text: /* makepng.c */
  #define _ISOC99_SOURCE
  /* Copyright: */
  #define COPYRIGHT "\251 2013,2015 John Cunningham Bowler"
  /*
   * This code is released under the libpng license.
   * For conditions of distribution and use, see the disclaimer
   * and license in png.h
   *
   * Make a test PNG image.  The arguments are as follows:
   *
   *    makepng [--sRGB|--linear|--1.8] [--tRNS] [--nofilters] \
   *       color-type bit-depth [file-name]
   *
   * The color-type may be numeric (and must match the numbers used by the PNG
   * specification) or one of the format names listed below.  The bit-depth is the
   * component bit depth, or the pixel bit-depth for a color-mapped image.
   *
   * Without any options no color-space information is written, with the options
   * an sRGB or the appropriate gAMA chunk is written.  "1.8" refers to the
   * display system used on older Apple computers to correct for high ambient
   * light levels in the viewing environment; it applies a transform of
   * approximately value^(1/1.45) to the color values and so a gAMA chunk of 65909
   * is written (1.45/2.2).
   *
   * The image data is generated internally.  Unless --color is given the images
   * used are as follows:
   *
   * 1 channel: a square image with a diamond, the least luminous colors are on
   *    the edge of the image, the most luminous in the center.
   *
   * 2 channels: the color channel increases in luminosity from top to bottom, the
   *    alpha channel increases in opacity from left to right.
   *
   * 3 channels: linear combinations of, from the top-left corner clockwise,
   *    black, green, white, red.
   *
   * 4 channels: linear combinations of, from the top-left corner clockwise,
   *    transparent, red, green, blue.
   *
   * For color-mapped images a four channel color-map is used and if --tRNS is
   * given the PNG file has a tRNS chunk, as follows:
   *
   * 1-bit: entry 0 is transparent-red, entry 1 is opaque-white
   * 2-bit: entry 0: transparent-green
   *        entry 1: 40%-red
   *        entry 2: 80%-blue
   *        entry 3: opaque-white
   * 4-bit: the 16 combinations of the 2-bit case
   * 8-bit: the 256 combinations of the 4-bit case
   *
   * The palette always has 2^bit-depth entries and the tRNS chunk one fewer.  The
   * image is the 1-channel diamond, but using palette index, not luminosity.
   *
   * For formats other than color-mapped ones if --tRNS is specified a tRNS chunk
   * is generated with all channels equal to the low bits of 0x0101.
   *
   * Image size is determined by the final pixel depth in bits, i.e. channels x
   * bit-depth, as follows:
   *
   * 8 bits or less:    64x64
   * 16 bits:           256x256
   * More than 16 bits: 1024x1024
   *
   * Row filtering is the libpng default but may be turned off (the 'none' filter
   * is used on every row) with the --nofilters option.
   *
   * The images are not interlaced.
   *
   * If file-name is given then the PNG is written to that file, else it is
   * written to stdout.  Notice that stdout is not supported on systems where, by
   * default, it assumes text output; this program makes no attempt to change the
   * text mode of stdout!
   *
   *    makepng --color=<color> ...
   *
   * If --color is given then the whole image has that color, color-mapped images
   * will have exactly one palette entry and all image files with be 16x16 in
   * size.  The color value is 1 to 4 decimal numbers as appropriate for the color
   * type.
   *
   *    makepng --small ...
   *
   * If --small is given the images are no larger than required to include every
   * possible pixel value for the format.
   *
   * For formats with pixels 8 bits or fewer in size the images consist of a
   * single row with 2^pixel-depth pixels, one of every possible value.
   *
   * For formats with 16-bit pixels a 256x256 image is generated containing every
   * possible pixel value.
   *
   * For larger pixel sizes a 256x256 image is generated where the first row
   * consists of each pixel that has identical byte values throughout the pixel
   * followed by rows where the byte values differ within the pixel.
   *
   * In all cases the pixel values are arranged in such a way that the SUB and UP
   * filters give byte sequences for maximal zlib compression.  By default (if
   * --nofilters is not given) the SUB filter is used on the first row and the UP
   * filter on all following rows.
   *
   * The --small option is meant to provide good test-case coverage, however the
   * images are not easy to examine visually.  Without the --small option the
   * images contain identical color values; the pixel values are adjusted
   * according to the gamma encoding with no gamma encoding being interpreted as
   * sRGB.
   *
   * LICENSING
   * =========
   *
   * This code is copyright of the authors, see the COPYRIGHT define above.  The
   * code is licensed as above, using the libpng license.  The code generates
   * images which are solely the product of the code; the options choose which of
   * the many possibilities to generate.  The images that result (but not the code
   * which generates them) are licensed as defined here:
   *
   * IMPORTANT: the COPYRIGHT #define must contain ISO-Latin-1 characters, the
   * IMAGE_LICENSING #define must contain UTF-8 characters.  The 'copyright'
   * symbol 0xA9U (\251) in ISO-Latin-1 encoding and 0xC20xA9 (\302\251) in UTF-8.
   */
  #define IMAGE_LICENSING "Dedicated to the public domain per Creative Commons "\
      "license \"CC0 1.0\"; https://creativecommons.org/publicdomain/zero/1.0/"
  
  #include <stddef.h> /* for offsetof */
  #include <stdlib.h>
  #include <stdio.h>
  #include <string.h>
  #include <ctype.h>
  #include <math.h>
  #include <errno.h>
  #include <assert.h>
  #include <stdint.h>
  
  #if defined(HAVE_CONFIG_H) && !defined(PNG_NO_CONFIG_H)
  #  include <config.h>
  #endif
  
  /* Define the following to use this test against your installed libpng, rather
   * than the one being built here:
   */
  #ifdef PNG_FREESTANDING_TESTS
  #  include <png.h>
  #else
  #  include "../.PNG/png.h"
  #endif
  
  #include <zlib.h>
  
  /* Work round for GCC complaints about casting a (double) function result to
   * an unsigned:
   */
  static unsigned int
  flooru(double d)
  {
     d = floor(d);
     return (unsigned int)d;
  }
  
  static png_byte
  floorb(double d)
  {
     d = floor(d);
     return (png_byte)d;
  }
  
  /* This structure is used for inserting extra chunks (the --insert argument, not
   * documented above.)
   */
  typedef struct chunk_insert
  {
     struct chunk_insert *next;
     void               (*insert)(png_structp, png_infop, int, png_charpp);
     int                  nparams;
     png_charp            parameters[1];
  } chunk_insert;
  
  static unsigned int
  channels_of_type(int color_type)
  {
     if (color_type & PNG_COLOR_MASK_PALETTE)
        return 1;
  
     else
     {
        int channels = 1;
  
        if (color_type & PNG_COLOR_MASK_COLOR)
           channels = 3;
  
        if (color_type & PNG_COLOR_MASK_ALPHA)
           return channels + 1;
  
        else
           return channels;
     }
  }
  
  static unsigned int
  pixel_depth_of_type(int color_type, int bit_depth)
  {
     return channels_of_type(color_type) * bit_depth;
  }
  
  static unsigned int
  image_size_of_type(int color_type, int bit_depth, unsigned int *colors,
     int small)
  {
     if (*colors)
        return 16;
  
     else
     {
        int pixel_depth = pixel_depth_of_type(color_type, bit_depth);
  
        if (small)
        {
           if (pixel_depth <= 8) /* there will be one row */
              return 1 << pixel_depth;
  
           else
              return 256;
        }
  
        else if (pixel_depth < 8)
           return 64;
  
        else if (pixel_depth > 16)
           return 1024;
  
        else
           return 256;
     }
  }
  
  static void
  set_color(png_colorp color, png_bytep trans, unsigned int red,
     unsigned int green, unsigned int blue, unsigned int alpha,
     png_const_bytep gamma_table)
  {
     color->red = gamma_table[red];
     color->green = gamma_table[green];
     color->blue = gamma_table[blue];
     *trans = (png_byte)alpha;
  }
  
  static int
  generate_palette(png_colorp palette, png_bytep trans, int bit_depth,
     png_const_bytep gamma_table, unsigned int *colors)
  {
     /*
      * 1-bit: entry 0 is transparent-red, entry 1 is opaque-white
      * 2-bit: entry 0: transparent-green
      *        entry 1: 40%-red
      *        entry 2: 80%-blue
      *        entry 3: opaque-white
      * 4-bit: the 16 combinations of the 2-bit case
      * 8-bit: the 256 combinations of the 4-bit case
      */
     switch (colors[0])
     {
        default:
           fprintf(stderr, "makepng: --colors=...: invalid count %u\n",
              colors[0]);
           exit(1);
  
        case 1:
           set_color(palette+0, trans+0, colors[1], colors[1], colors[1], 255,
              gamma_table);
           return 1;
  
        case 2:
           set_color(palette+0, trans+0, colors[1], colors[1], colors[1],
              colors[2], gamma_table);
           return 1;
  
        case 3:
           set_color(palette+0, trans+0, colors[1], colors[2], colors[3], 255,
              gamma_table);
           return 1;
  
        case 4:
           set_color(palette+0, trans+0, colors[1], colors[2], colors[3],
              colors[4], gamma_table);
           return 1;
  
        case 0:
           if (bit_depth == 1)
           {
              set_color(palette+0, trans+0, 255, 0, 0, 0, gamma_table);
              set_color(palette+1, trans+1, 255, 255, 255, 255, gamma_table);
              return 2;
           }
  
           else
           {
              unsigned int size = 1U << (bit_depth/2); /* 2, 4 or 16 */
              unsigned int x, y;
              volatile unsigned int ip = 0;
  
              for (x=0; x<size; ++x)
              {
                 for (y=0; y<size; ++y)
                 {
                    ip = x + (size * y);
  
                    /* size is at most 16, so the scaled value below fits in 16 bits
                    */
  #                 define interp(pos, c1, c2) ((pos * c1) + ((size-pos) * c2))
  #                 define xyinterp(x, y, c1, c2, c3, c4) (((size * size / 2) +\
                       (interp(x, c1, c2) * y + (size-y) * interp(x, c3, c4))) /\
                       (size*size))
  
                    set_color(palette+ip, trans+ip,
                       /* color:    green, red,blue,white */
                       xyinterp(x, y,   0, 255,   0, 255),
                       xyinterp(x, y, 255,   0,   0, 255),
                       xyinterp(x, y,   0,   0, 255, 255),
                       /* alpha:        0, 102, 204, 255) */
                       xyinterp(x, y,   0, 102, 204, 255),
                       gamma_table);
                 }
              }
  
              return ip+1;
           }
     }
  }
  
  static void
  set_value(png_bytep row, size_t rowbytes, png_uint_32 x, unsigned int bit_depth,
     png_uint_32 value, png_const_bytep gamma_table, double conv)
  {
     unsigned int mask = (1U << bit_depth)-1;
  
     x *= bit_depth;  /* Maximum x is 4*1024, maximum bit_depth is 16 */
  
     if (value <= mask)
     {
        png_uint_32 offset = x >> 3;
  
        if (offset < rowbytes && (bit_depth < 16 || offset+1 < rowbytes))
        {
           row += offset;
  
           switch (bit_depth)
           {
              case 1:
              case 2:
              case 4:
                 /* Don't gamma correct - values get smashed */
                 {
                    unsigned int shift = (8 - bit_depth) - (x & 0x7U);
  
                    mask <<= shift;
                    value = (value << shift) & mask;
                    *row = (png_byte)((*row & ~mask) | value);
                 }
                 return;
  
              default:
                 fprintf(stderr, "makepng: bad bit depth (internal error)\n");
                 exit(1);
  
              case 16:
                 value = flooru(65535*pow(value/65535.,conv)+.5);
                 *row++ = (png_byte)(value >> 8);
                 *row = (png_byte)value;
                 return;
  
              case 8:
                 *row = gamma_table[value];
                 return;
           }
        }
  
        else
        {
           fprintf(stderr, "makepng: row buffer overflow (internal error)\n");
           exit(1);
        }
     }
  
     else
     {
        fprintf(stderr, "makepng: component overflow (internal error)\n");
        exit(1);
     }
  }
  
  static int /* filter mask for row */
  generate_row(png_bytep row, size_t rowbytes, unsigned int y, int color_type,
     int bit_depth, png_const_bytep gamma_table, double conv,
     unsigned int *colors, int small)
  {
     int filters = 0; /* file *MASK*, 0 means the default, not NONE */
     png_uint_32 size_max =
        image_size_of_type(color_type, bit_depth, colors, small)-1;
     png_uint_32 depth_max = (1U << bit_depth)-1; /* up to 65536 */
  
     if (colors[0] == 0 && small)
     {
        unsigned int pixel_depth = pixel_depth_of_type(color_type, bit_depth);
  
        /* For pixel depths less than 16 generate a single row containing all the
         * possible pixel values.  For 16 generate all 65536 byte pair
         * combinations in a 256x256 pixel array.
         */
        switch (pixel_depth)
        {
           case 1:
              assert(y == 0 && rowbytes == 1 && size_max == 1);
              row[0] = 0x6CU; /* binary: 01101100, only top 2 bits used */
              filters = PNG_FILTER_NONE;
              break;
  
           case 2:
              assert(y == 0 && rowbytes == 1 && size_max == 3);
              row[0] = 0x1BU; /* binary 00011011, all bits used */
              filters = PNG_FILTER_NONE;
              break;
  
           case 4:
              assert(y == 0 && rowbytes == 8 && size_max == 15);
              row[0] = 0x01U;
              row[1] = 0x23U; /* SUB gives 0x22U for all following bytes */
              row[2] = 0x45U;
              row[3] = 0x67U;
              row[4] = 0x89U;
              row[5] = 0xABU;
              row[6] = 0xCDU;
              row[7] = 0xEFU;
              filters = PNG_FILTER_SUB;
              break;
  
           case 8:
              /* The row will have all the pixel values in order starting with
               * '1', the SUB filter will change every byte into '1' (including
               * the last, which generates pixel value '0').  Since the SUB filter
               * has value 1 this should result in maximum compression.
               */
              assert(y == 0 && rowbytes == 256 && size_max == 255);
              for (;;)
              {
                 row[size_max] = 0xFFU & (size_max+1);
                 if (size_max == 0)
                    break;
                 --size_max;
              }
              filters = PNG_FILTER_SUB;
              break;
  
           case 16:
              /* Rows are generated such that each row has a constant difference
               * between the first and second byte of each pixel and so that the
               * difference increases by 1 at each row.  The rows start with the
               * first byte value of 0 and the value increases to 255 across the
               * row.
               *
               * The difference starts at 1, so the first row is:
               *
               *     0 1 1 2 2 3 3 4 ... 254 255 255 0
               *
               * This means that running the SUB filter on the first row produces:
               *
               *   [SUB==1] 0 1 0 1 0 1...
               *
               * Then the difference is 2 on the next row, giving:
               *
               *    0 2 1 3 2 4 3 5 ... 254 0 255 1
               *
               * When the UP filter is run on this libpng produces:
               *
               *   [UP ==2] 0 1 0 1 0 1...
               *
               * And so on for all the remain rows to the final two * rows:
               *
               *    row 254: 0 255 1 0 2 1 3 2 4 3 ... 254 253 255 254
               *    row 255: 0   0 1 1 2 2 3 3 4 4 ... 254 254 255 255
               */
              assert(rowbytes == 512 && size_max == 255);
              for (;;)
              {
                 row[2*size_max  ] = 0xFFU & size_max;
                 row[2*size_max+1] = 0xFFU & (size_max+y+1);
                 if (size_max == 0)
                    break;
                 --size_max;
              }
              /* The first row must include PNG_FILTER_UP so that libpng knows we
               * need to keep it for the following row:
               */
              filters = (y == 0 ? PNG_FILTER_SUB+PNG_FILTER_UP : PNG_FILTER_UP);
              break;
  
           case 24:
           case 32:
           case 48:
           case 64:
              /* The rows are filled by an alogorithm similar to the above, in the
               * first row pixel bytes are all equal, increasing from 0 by 1 for
               * each pixel.  In the second row the bytes within a pixel are
               * incremented 1,3,5,7,... from the previous row byte.  Using an odd
               * number ensures all the possible byte values are used.
               */
              assert(size_max == 255 && rowbytes == 256*(pixel_depth>>3));
              pixel_depth >>= 3; /* now in bytes */
              while (rowbytes > 0)
              {
                 const size_t pixel_index = --rowbytes/pixel_depth;
  
                 if (y == 0)
                    row[rowbytes] = 0xFFU & pixel_index;
  
                 else
                 {
                    const size_t byte_offset =
                       rowbytes - pixel_index * pixel_depth;
  
                    row[rowbytes] =
                       0xFFU & (pixel_index + (byte_offset * 2*y) + 1);
                 }
              }
              filters = (y == 0 ? PNG_FILTER_SUB+PNG_FILTER_UP : PNG_FILTER_UP);
              break;
  
           default:
              assert(0/*NOT REACHED*/);
        }
     }
  
     else switch (channels_of_type(color_type))
     {
     /* 1 channel: a square image with a diamond, the least luminous colors are on
      *    the edge of the image, the most luminous in the center.
      */
        case 1:
           {
              png_uint_32 x;
              png_uint_32 base = 2*size_max - abs(2*y-size_max);
  
              for (x=0; x<=size_max; ++x)
              {
                 png_uint_32 luma = base - abs(2*x-size_max);
  
                 /* 'luma' is now in the range 0..2*size_max, we need
                  * 0..depth_max
                  */
                 luma = (luma*depth_max + size_max) / (2*size_max);
                 set_value(row, rowbytes, x, bit_depth, luma, gamma_table, conv);
              }
           }
           break;
  
     /* 2 channels: the color channel increases in luminosity from top to bottom,
      *    the alpha channel increases in opacity from left to right.
      */
        case 2:
           {
              png_uint_32 alpha = (depth_max * y * 2 + size_max) / (2 * size_max);
              png_uint_32 x;
  
              for (x=0; x<=size_max; ++x)
              {
                 set_value(row, rowbytes, 2*x, bit_depth,
                    (depth_max * x * 2 + size_max) / (2 * size_max), gamma_table,
                    conv);
                 set_value(row, rowbytes, 2*x+1, bit_depth, alpha, gamma_table,
                    conv);
              }
           }
           break;
  
     /* 3 channels: linear combinations of, from the top-left corner clockwise,
      *    black, green, white, red.
      */
        case 3:
           {
              /* x0: the black->red scale (the value of the red component) at the
               *     start of the row (blue and green are 0).
               * x1: the green->white scale (the value of the red and blue
               *     components at the end of the row; green is depth_max).
               */
              png_uint_32 Y = (depth_max * y * 2 + size_max) / (2 * size_max);
              png_uint_32 x;
  
              /* Interpolate x/depth_max from start to end:
               *
               *        start end         difference
               * red:     Y    Y            0
               * green:   0   depth_max   depth_max
               * blue:    0    Y            Y
               */
              for (x=0; x<=size_max; ++x)
              {
                 set_value(row, rowbytes, 3*x+0, bit_depth, /* red */ Y,
                       gamma_table, conv);
                 set_value(row, rowbytes, 3*x+1, bit_depth, /* green */
                    (depth_max * x * 2 + size_max) / (2 * size_max),
                    gamma_table, conv);
                 set_value(row, rowbytes, 3*x+2, bit_depth, /* blue */
                    (Y * x * 2 + size_max) / (2 * size_max),
                    gamma_table, conv);
              }
           }
           break;
  
     /* 4 channels: linear combinations of, from the top-left corner clockwise,
      *    transparent, red, green, blue.
      */
        case 4:
           {
              /* x0: the transparent->blue scale (the value of the blue and alpha
               *     components) at the start of the row (red and green are 0).
               * x1: the red->green scale (the value of the red and green
               *     components at the end of the row; blue is 0 and alpha is
               *     depth_max).
               */
              png_uint_32 Y = (depth_max * y * 2 + size_max) / (2 * size_max);
              png_uint_32 x;
  
              /* Interpolate x/depth_max from start to end:
               *
               *        start    end       difference
               * red:     0   depth_max-Y depth_max-Y
               * green:   0       Y             Y
               * blue:    Y       0            -Y
               * alpha:   Y    depth_max  depth_max-Y
               */
              for (x=0; x<=size_max; ++x)
              {
                 set_value(row, rowbytes, 4*x+0, bit_depth, /* red */
                    ((depth_max-Y) * x * 2 + size_max) / (2 * size_max),
                    gamma_table, conv);
                 set_value(row, rowbytes, 4*x+1, bit_depth, /* green */
                    (Y * x * 2 + size_max) / (2 * size_max),
                    gamma_table, conv);
                 set_value(row, rowbytes, 4*x+2, bit_depth, /* blue */
                    Y - (Y * x * 2 + size_max) / (2 * size_max),
                    gamma_table, conv);
                 set_value(row, rowbytes, 4*x+3, bit_depth, /* alpha */
                    Y + ((depth_max-Y) * x * 2 + size_max) / (2 * size_max),
                    gamma_table, conv);
              }
           }
           break;
  
        default:
           fprintf(stderr, "makepng: internal bad channel count\n");
           exit(2);
     }
  
     else if (color_type & PNG_COLOR_MASK_PALETTE)
     {
        /* Palette with fixed color: the image rows are all 0 and the image width
         * is 16.
         */
        memset(row, 0, rowbytes);
     }
  
     else if (colors[0] == channels_of_type(color_type))
        switch (channels_of_type(color_type))
        {
           case 1:
              {
                 png_uint_32 luma = colors[1];
                 png_uint_32 x;
  
                 for (x=0; x<=size_max; ++x)
                    set_value(row, rowbytes, x, bit_depth, luma, gamma_table,
                       conv);
              }
              break;
  
           case 2:
              {
                 png_uint_32 luma = colors[1];
                 png_uint_32 alpha = colors[2];
                 png_uint_32 x;
  
                 for (x=0; x<size_max; ++x)
                 {
                    set_value(row, rowbytes, 2*x, bit_depth, luma, gamma_table,
                       conv);
                    set_value(row, rowbytes, 2*x+1, bit_depth, alpha, gamma_table,
                       conv);
                 }
              }
              break;
  
           case 3:
              {
                 png_uint_32 red = colors[1];
                 png_uint_32 green = colors[2];
                 png_uint_32 blue = colors[3];
                 png_uint_32 x;
  
                 for (x=0; x<=size_max; ++x)
                 {
                    set_value(row, rowbytes, 3*x+0, bit_depth, red, gamma_table,
                       conv);
                    set_value(row, rowbytes, 3*x+1, bit_depth, green, gamma_table,
                       conv);
                    set_value(row, rowbytes, 3*x+2, bit_depth, blue, gamma_table,
                       conv);
                 }
              }
              break;
  
           case 4:
              {
                 png_uint_32 red = colors[1];
                 png_uint_32 green = colors[2];
                 png_uint_32 blue = colors[3];
                 png_uint_32 alpha = colors[4];
                 png_uint_32 x;
  
                 for (x=0; x<=size_max; ++x)
                 {
                    set_value(row, rowbytes, 4*x+0, bit_depth, red, gamma_table,
                       conv);
                    set_value(row, rowbytes, 4*x+1, bit_depth, green, gamma_table,
                       conv);
                    set_value(row, rowbytes, 4*x+2, bit_depth, blue, gamma_table,
                       conv);
                    set_value(row, rowbytes, 4*x+3, bit_depth, alpha, gamma_table,
                       conv);
                 }
              }
           break;
  
           default:
              fprintf(stderr, "makepng: internal bad channel count\n");
              exit(2);
        }
  
     else
     {
        fprintf(stderr,
           "makepng: --color: count(%u) does not match channels(%u)\n",
           colors[0], channels_of_type(color_type));
        exit(1);
     }
  
     return filters;
  }
  
  
  static void PNGCBAPI
  makepng_warning(png_structp png_ptr, png_const_charp message)
  {
     const char **ep = png_get_error_ptr(png_ptr);
     const char *name;
  
     if (ep != NULL && *ep != NULL)
        name = *ep;
  
     else
        name = "makepng";
  
    fprintf(stderr, "%s: warning: %s\n", name, message);
  }
  
  static void PNGCBAPI
  makepng_error(png_structp png_ptr, png_const_charp message)
  {
     makepng_warning(png_ptr, message);
     png_longjmp(png_ptr, 1);
  }
  
  static int /* 0 on success, else an error code */
  write_png(const char **name, FILE *fp, int color_type, int bit_depth,
     volatile png_fixed_point gamma, chunk_insert * volatile insert,
     unsigned int filters, unsigned int *colors, int small, int tRNS)
  {
     png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
        name, makepng_error, makepng_warning);
     volatile png_infop info_ptr = NULL;
     volatile png_bytep row = NULL;
  
     if (png_ptr == NULL)
     {
        fprintf(stderr, "makepng: OOM allocating write structure\n");
        return 1;
     }
  
     if (setjmp(png_jmpbuf(png_ptr)))
     {
        png_structp nv_ptr = png_ptr;
        png_infop nv_info = info_ptr;
  
        png_ptr = NULL;
        info_ptr = NULL;
        png_destroy_write_struct(&nv_ptr, &nv_info);
        if (row != NULL) free(row);
        return 1;
     }
  
     /* Allow benign errors so that we can write PNGs with errors */
     png_set_benign_errors(png_ptr, 1/*allowed*/);
  
     /* Max out the text compression level in an attempt to make the license
      * small.   If --small then do the same for the IDAT.
      */
     if (small)
        png_set_compression_level(png_ptr, Z_BEST_COMPRESSION);
  
     png_set_text_compression_level(png_ptr, Z_BEST_COMPRESSION);
  
     png_init_io(png_ptr, fp);
  
     info_ptr = png_create_info_struct(png_ptr);
     if (info_ptr == NULL)
        png_error(png_ptr, "OOM allocating info structure");
  
     {
        unsigned int size =
           image_size_of_type(color_type, bit_depth, colors, small);
        unsigned int ysize;
        png_fixed_point real_gamma = 45455; /* For sRGB */
        png_byte gamma_table[256];
        double conv;
  
        /* Normally images are square, but with 'small' we want to simply generate
         * all the pixel values, or all that we reasonably can:
         */
        if (small)
        {
           unsigned int pixel_depth =
              pixel_depth_of_type(color_type, bit_depth);
  
           if (pixel_depth <= 8U)
           {
              assert(size == (1U<<pixel_depth));
              ysize = 1U;
           }
  
           else
           {
              assert(size == 256U);
              ysize = 256U;
           }
        }
  
        else
           ysize = size;
  
        /* This function uses the libpng values used on read to carry extra
         * information about the gamma:
         */
        if (gamma == PNG_GAMMA_MAC_18)
           gamma = 65909;
  
        else if (gamma > 0 && gamma < 1000)
           gamma = PNG_FP_1;
  
        if (gamma > 0)
           real_gamma = gamma;
  
        {
           unsigned int i;
  
           if (real_gamma == 45455)
           {
              for (i=0; i<256; ++i)
              {
                 gamma_table[i] = (png_byte)i;
                 conv = 1.;
              }
           }
  
           else
           {
              /* Convert 'i' from sRGB (45455) to real_gamma, this makes
               * the images look the same regardless of the gAMA chunk.
               */
              conv = real_gamma;
              conv /= 45455;
  
              gamma_table[0] = 0;
  
              for (i=1; i<255; ++i)
                 gamma_table[i] = floorb(pow(i/255.,conv) * 255 + .5);
  
              gamma_table[255] = 255;
           }
        }
  
        png_set_IHDR(png_ptr, info_ptr, size, ysize, bit_depth, color_type,
           PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
  
        if (color_type & PNG_COLOR_MASK_PALETTE)
        {
           int npalette;
           png_color palette[256];
           png_byte trans[256];
  
           npalette = generate_palette(palette, trans, bit_depth, gamma_table,
              colors);
           png_set_PLTE(png_ptr, info_ptr, palette, npalette);
  
           if (tRNS)
              png_set_tRNS(png_ptr, info_ptr, trans, npalette-1,
                 NULL/*transparent color*/);
  
           /* Reset gamma_table to prevent the image rows being changed */
           for (npalette=0; npalette<256; ++npalette)
              gamma_table[npalette] = (png_byte)npalette;
        }
  
        else if (tRNS)
        {
           png_color_16 col;
  
           col.red = col.green = col.blue = col.gray =
              0x0101U & ((1U<<bit_depth)-1U);
           col.index = 0U;
           png_set_tRNS(png_ptr, info_ptr, NULL/*trans*/, 1U, &col);
        }
  
        if (gamma == PNG_DEFAULT_sRGB)
           png_set_sRGB(png_ptr, info_ptr, PNG_sRGB_INTENT_ABSOLUTE);
  
        else if (gamma > 0) /* Else don't set color space information */
        {
           png_set_gAMA_fixed(png_ptr, info_ptr, real_gamma);
  
           /* Just use the sRGB values here. */
           png_set_cHRM_fixed(png_ptr, info_ptr,
              /* color      x       y */
              /* white */ 31270, 32900,
              /* red   */ 64000, 33000,
              /* green */ 30000, 60000,
              /* blue  */ 15000,  6000
           );
        }
  
        /* Insert extra information. */
        while (insert != NULL)
        {
           insert->insert(png_ptr, info_ptr, insert->nparams, insert->parameters);
           insert = insert->next;
        }
  
        /* Write the file header. */
        png_write_info(png_ptr, info_ptr);
  
        /* Restrict the filters */
        png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, filters);
  
        {
  #        ifdef PNG_WRITE_INTERLACING_SUPPORTED
              int passes = png_set_interlace_handling(png_ptr);
  #        else /* !WRITE_INTERLACING */
              int passes = 1;
  #        endif /* !WRITE_INTERLACING */
           int pass;
           size_t rowbytes = png_get_rowbytes(png_ptr, info_ptr);
  
           row = malloc(rowbytes);
  
           if (row == NULL)
              png_error(png_ptr, "OOM allocating row buffer");
  
           for (pass = 0; pass < passes; ++pass)
           {
              unsigned int y;
  
              for (y=0; y<ysize; ++y)
              {
                 unsigned int row_filters =
                    generate_row(row, rowbytes, y, color_type, bit_depth,
                          gamma_table, conv, colors, small);
  
                 if (row_filters != 0 && filters == PNG_ALL_FILTERS)
                    png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, row_filters);
  
                 png_write_row(png_ptr, row);
              }
           }
        }
     }
  
     /* Finish writing the file. */
     png_write_end(png_ptr, info_ptr);
  
     {
        png_structp nv_ptr = png_ptr;
        png_infop nv_info = info_ptr;
  
        png_ptr = NULL;
        info_ptr = NULL;
        png_destroy_write_struct(&nv_ptr, &nv_info);
     }
     free(row);
     return 0;
  }
  
  
  static size_t
  load_file(png_const_charp name, png_bytepp result)
  {
     FILE *fp = tmpfile();
  
     if (fp != NULL)
     {
        FILE *ip = fopen(name, "rb");
  
        if (ip != NULL)
        {
           size_t total = 0;
           int ch;
  
           for (;;)
           {
              ch = getc(ip);
              if (ch == EOF) break;
              putc(ch, fp);
              ++total;
           }
  
           if (ferror(ip))
           {
              perror(name);
              fprintf(stderr, "%s: read error\n", name);
              (void)fclose(ip);
           }
  
           else
           {
              (void)fclose(ip);
  
              if (ferror(fp))
              {
                 perror("temporary file");
                 fprintf(stderr, "temporary file write error\n");
              }
  
              else
              {
                 rewind(fp);
  
                 if (total > 0)
                 {
                    /* Round up to a multiple of 4 here to allow an iCCP profile
                     * to be padded to a 4x boundary.
                     */
                    png_bytep data = malloc((total+3)&~3);
  
                    if (data != NULL)
                    {
                       size_t new_size = 0;
  
                       for (;;)
                       {
                          ch = getc(fp);
                          if (ch == EOF) break;
                          data[new_size++] = (png_byte)ch;
                       }
  
                       if (ferror(fp) || new_size != total)
                       {
                          perror("temporary file");
                          fprintf(stderr, "temporary file read error\n");
                          free(data);
                       }
  
                       else
                       {
                          (void)fclose(fp);
                          *result = data;
                          return total;
                       }
                    }
  
                    else
                       fprintf(stderr, "%s: out of memory loading file\n", name);
                 }
  
                 else
                    fprintf(stderr, "%s: empty file\n", name);
              }
           }
        }
  
        else
        {
           perror(name);
           fprintf(stderr, "%s: open failed\n", name);
        }
  
        fclose(fp);
     }
  
     else
        fprintf(stderr, "makepng: %s: could not open temporary file\n", name);
  
     exit(1);
     return 0;
  }
  
  static size_t
  load_fake(png_charp param, png_bytepp profile)
  {
     char *endptr = NULL;
     uint64_t size = strtoull(param, &endptr, 0/*base*/);
  
     /* The 'fake' format is <number>*[string] */
     if (endptr != NULL && *endptr == '*')
     {
        size_t len = strlen(++endptr);
        size_t result = (size_t)size;
  
        if (len == 0) len = 1; /* capture the terminating '\0' */
  
        /* Now repeat that string to fill 'size' bytes. */
        if (result == size && (*profile = malloc(result)) != NULL)
        {
           png_bytep out = *profile;
  
           if (len == 1)
              memset(out, *endptr, result);
  
           else
           {
              while (size >= len)
              {
                 memcpy(out, endptr, len);
                 out += len;
                 size -= len;
              }
              memcpy(out, endptr, size);
           }
  
           return result;
        }
  
        else
        {
           fprintf(stderr, "%s: size exceeds system limits\n", param);
           exit(1);
        }
     }
  
     return 0;
  }
  
  static void
  check_param_count(int nparams, int expect)
  {
     if (nparams != expect)
     {
        fprintf(stderr, "bad parameter count (internal error)\n");
        exit(1);
     }
  }
  
  static void
  insert_iCCP(png_structp png_ptr, png_infop info_ptr, int nparams,
     png_charpp params)
  {
     png_bytep profile = NULL;
     png_uint_32 proflen = 0;
     int result;
  
     check_param_count(nparams, 2);
  
     switch (params[1][0])
     {
        case '<':
           {
              size_t filelen = load_file(params[1]+1, &profile);
              if (filelen > 0xfffffffc) /* Maximum profile length */
              {
                 fprintf(stderr, "%s: file too long (%lu) for an ICC profile\n",
                    params[1]+1, (unsigned long)filelen);
                 exit(1);
              }
  
              proflen = (png_uint_32)filelen;
           }
           break;
  
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
           {
              size_t fake_len = load_fake(params[1], &profile);
  
              if (fake_len > 0) /* else a simple parameter */
              {
                 if (fake_len > 0xffffffff) /* Maximum profile length */
                 {
                    fprintf(stderr,
                       "%s: fake data too long (%lu) for an ICC profile\n",
                       params[1], (unsigned long)fake_len);
                    exit(1);
                 }
                 proflen = (png_uint_32)(fake_len & ~3U);
                 /* Always fix up the profile length. */
                 png_save_uint_32(profile, proflen);
                 break;
              }
           }
  
        default:
           fprintf(stderr, "--insert iCCP \"%s\": unrecognized\n", params[1]);
           fprintf(stderr, "  use '<' to read a file: \"<filename\"\n");
           exit(1);
     }
  
     result = 1;
  
     if (proflen & 3)
     {
        fprintf(stderr,
           "makepng: --insert iCCP %s: profile length made a multiple of 4\n",
           params[1]);
  
        /* load_file allocates extra space for this padding, the ICC spec requires
         * padding with zero bytes.
         */
        while (proflen & 3)
           profile[proflen++] = 0;
     }
  
     if (profile != NULL && proflen > 3)
     {
        png_uint_32 prof_header = png_get_uint_32(profile);
  
        if (prof_header != proflen)
        {
           fprintf(stderr, "--insert iCCP %s: profile length field wrong:\n",
              params[1]);
           fprintf(stderr, "  actual %lu, recorded value %lu (corrected)\n",
              (unsigned long)proflen, (unsigned long)prof_header);
           png_save_uint_32(profile, proflen);
        }
     }
  
     if (result && profile != NULL && proflen >=4)
        png_set_iCCP(png_ptr, info_ptr, params[0], PNG_COMPRESSION_TYPE_BASE,
           profile, proflen);
  
     if (profile)
        free(profile);
  
     if (!result)
        exit(1);
  }
  
  static void
  clear_text(png_text *text, png_charp keyword)
  {
     text->compression = -1; /* none */
     text->key = keyword;
     text->text = NULL;
     text->text_length = 0; /* libpng calculates this */
     text->itxt_length = 0; /* libpng calculates this */
     text->lang = NULL;
     text->lang_key = NULL;
  }
  
  static void
  set_text(png_structp png_ptr, png_infop info_ptr, png_textp text,
     png_charp param)
  {
     switch (param[0])
     {
        case '<':
           {
              png_bytep file = NULL;
  
              text->text_length = load_file(param+1, &file);
              text->text = (png_charp)file;
           }
           break;
  
        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
           {
              png_bytep data = NULL;
              size_t fake_len = load_fake(param, &data);
  
              if (fake_len > 0) /* else a simple parameter */
              {
                 text->text_length = fake_len;
                 text->text = (png_charp)data;
                 break;
              }
           }
  
        default:
           text->text = param;
           break;
     }
  
     png_set_text(png_ptr, info_ptr, text, 1);
  
     if (text->text != param)
        free(text->text);
  }
  
  static void
  insert_tEXt(png_structp png_ptr, png_infop info_ptr, int nparams,
     png_charpp params)
  {
     png_text text;
  
     check_param_count(nparams, 2);
     clear_text(&text, params[0]);
     set_text(png_ptr, info_ptr, &text, params[1]);
  }
  
  static void
  insert_zTXt(png_structp png_ptr, png_infop info_ptr, int nparams,
     png_charpp params)
  {
     png_text text;
  
     check_param_count(nparams, 2);
     clear_text(&text, params[0]);
     text.compression = 0; /* deflate */
     set_text(png_ptr, info_ptr, &text, params[1]);
  }
  
  static void
  insert_iTXt(png_structp png_ptr, png_infop info_ptr, int nparams,
     png_charpp params)
  {
     png_text text;
  
     check_param_count(nparams, 4);
     clear_text(&text, params[0]);
     text.compression = 2; /* iTXt + deflate */
     text.lang = params[1];/* language tag */
     text.lang_key = params[2]; /* translated keyword */
     set_text(png_ptr, info_ptr, &text, params[3]);
  }
  
  static void
  insert_hIST(png_structp png_ptr, png_infop info_ptr, int nparams,
        png_charpp params)
  {
     int i;
     png_uint_16 freq[256];
  
     /* libpng takes the count from the PLTE count; we don't check it here but we
      * do set the array to 0 for unspecified entries.
      */
     memset(freq, 0, sizeof freq);
     for (i=0; i<nparams; ++i)
     {
        char *endptr = NULL;
        unsigned long int l = strtoul(params[i], &endptr, 0/*base*/);
  
        if (params[i][0] && *endptr == 0 && l <= 65535)
           freq[i] = (png_uint_16)l;
  
        else
        {
           fprintf(stderr, "hIST[%d]: %s: invalid frequency\n", i, params[i]);
           exit(1);
        }
     }
  
     png_set_hIST(png_ptr, info_ptr, freq);
  }
  
  static png_byte
  bval(png_const_structrp png_ptr, png_charp param, unsigned int maxval)
  {
     char *endptr = NULL;
     unsigned long int l = strtoul(param, &endptr, 0/*base*/);
  
     if (param[0] && *endptr == 0 && l <= maxval)
        return (png_byte)l;
  
     else
        png_error(png_ptr, "sBIT: invalid sBIT value");
  }
  
  static void
  insert_sBIT(png_structp png_ptr, png_infop info_ptr, int nparams,
        png_charpp params)
  {
     int ct = png_get_color_type(png_ptr, info_ptr);
     int c = (ct & PNG_COLOR_MASK_COLOR ? 3 : 1) +
        (ct & PNG_COLOR_MASK_ALPHA ? 1 : 0);
     unsigned int maxval =
        ct & PNG_COLOR_MASK_PALETTE ? 8U : png_get_bit_depth(png_ptr, info_ptr);
     png_color_8 sBIT;
  
     if (nparams != c)
        png_error(png_ptr, "sBIT: incorrect parameter count");
  
     if (ct & PNG_COLOR_MASK_COLOR)
     {
        sBIT.red = bval(png_ptr, params[0], maxval);
        sBIT.green = bval(png_ptr, params[1], maxval);
        sBIT.blue = bval(png_ptr, params[2], maxval);
        sBIT.gray = 42;
     }
  
     else
     {
        sBIT.red = sBIT.green = sBIT.blue = 42;
        sBIT.gray = bval(png_ptr, params[0], maxval);
     }
  
     if (ct & PNG_COLOR_MASK_ALPHA)
        sBIT.alpha = bval(png_ptr, params[nparams-1], maxval);
  
     else
        sBIT.alpha = 42;
  
     png_set_sBIT(png_ptr, info_ptr, &sBIT);
  }
  
  #if 0
  static void
  insert_sPLT(png_structp png_ptr, png_infop info_ptr, int nparams, png_charpp params)
  {
     fprintf(stderr, "insert sPLT: NYI\n");
  }
  #endif
  
  static int
  find_parameters(png_const_charp what, png_charp param, png_charp *list,
     int nparams)
  {
     /* Parameters are separated by '\n' or ':' characters, up to nparams are
      * accepted (more is an error) and the number found is returned.
      */
     int i;
     for (i=0; *param && i<nparams; ++i)
     {
        list[i] = param;
        while (*++param)
        {
           if (*param == '\n' || *param == ':')
           {
              *param++ = 0; /* Terminate last parameter */
              break;        /* And start a new one. */
           }
        }
     }
  
     if (*param)
     {
        fprintf(stderr, "--insert %s: too many parameters (%s)\n", what, param);
        exit(1);
     }
  
     list[i] = NULL; /* terminates list */
     return i; /* number of parameters filled in */
  }
  
  static void
  bad_parameter_count(png_const_charp what, int nparams)
  {
     fprintf(stderr, "--insert %s: bad parameter count %d\n", what, nparams);
     exit(1);
  }
  
  static chunk_insert *
  make_insert(png_const_charp what,
     void (*insert)(png_structp, png_infop, int, png_charpp),
     int nparams, png_charpp list)
  {
     int i;
     chunk_insert *cip;
  
     cip = malloc(offsetof(chunk_insert,parameters) +
        nparams * sizeof (png_charp));
  
     if (cip == NULL)
     {
        fprintf(stderr, "--insert %s: out of memory allocating %d parameters\n",
           what, nparams);
        exit(1);
     }
  
     cip->next = NULL;
     cip->insert = insert;
     cip->nparams = nparams;
     for (i=0; i<nparams; ++i)
        cip->parameters[i] = list[i];
  
     return cip;
  }
  
  static chunk_insert *
  find_insert(png_const_charp what, png_charp param)
  {
     png_uint_32 chunk = 0;
     png_charp parameter_list[1024];
     int i, nparams;
  
     /* Assemble the chunk name */
     for (i=0; i<4; ++i)
     {
        char ch = what[i];
  
        if ((ch >= 65 && ch <= 90) || (ch >= 97 && ch <= 122))
           chunk = (chunk << 8) + what[i];
  
        else
           break;
     }
  
     if (i < 4 || what[4] != 0)
     {
        fprintf(stderr, "makepng --insert \"%s\": invalid chunk name\n", what);
        exit(1);
     }
  
     /* Assemble the parameter list. */
     nparams = find_parameters(what, param, parameter_list, 1024);
  
  #  define CHUNK(a,b,c,d) (((a)<<24)+((b)<<16)+((c)<<8)+(d))
  
     switch (chunk)
     {
        case CHUNK(105,67,67,80):  /* iCCP */
           if (nparams == 2)
              return make_insert(what, insert_iCCP, nparams, parameter_list);
           break;
  
        case CHUNK(116,69,88,116): /* tEXt */
           if (nparams == 2)
              return make_insert(what, insert_tEXt, nparams, parameter_list);
           break;
  
        case CHUNK(122,84,88,116): /* zTXt */
           if (nparams == 2)
              return make_insert(what, insert_zTXt, nparams, parameter_list);
           break;
  
        case CHUNK(105,84,88,116): /* iTXt */
           if (nparams == 4)
              return make_insert(what, insert_iTXt, nparams, parameter_list);
           break;
  
        case CHUNK(104,73,83,84):  /* hIST */
           if (nparams <= 256)
              return make_insert(what, insert_hIST, nparams, parameter_list);
           break;
  
        case CHUNK(115,66,73,84): /* sBIT */
           if (nparams <= 4)
              return make_insert(what, insert_sBIT, nparams, parameter_list);
           break;
  
  #if 0
        case CHUNK(115,80,76,84):  /* sPLT */
           return make_insert(what, insert_sPLT, nparams, parameter_list);
  #endif
  
        default:
           fprintf(stderr, "makepng --insert \"%s\": unrecognized chunk name\n",
              what);
           exit(1);
     }
  
     bad_parameter_count(what, nparams);
     return NULL;
  }
  
  /* This is necessary because libpng expects writeable strings for things like
   * text chunks (maybe this should be fixed...)
   */
  static png_charp
  strstash(png_const_charp foo)
  {
     /* The program indicates a memory allocation error by crashing, this is by
      * design.
      */
     if (foo != NULL)
     {
        png_charp bar = malloc(strlen(foo)+1);
        return strcpy(bar, foo);
     }
  
     return NULL;
  }
  
  static png_charp
  strstash_list(const png_const_charp *text)
  {
     size_t foo = 0;
     png_charp result, bar;
     const png_const_charp *line = text;
  
     while (*line != NULL)
        foo += strlen(*line++);
  
     result = bar = malloc(foo+1);
  
     line = text;
     while (*line != NULL)
     {
        foo = strlen(*line);
        memcpy(bar, *line++, foo);
        bar += foo;
     }
  
     *bar = 0;
     return result;
  }
  
  /* These are used to insert Copyright and Licence fields, they allow the text to
   * have \n unlike the --insert option.
   */
  static chunk_insert *
  add_tEXt(const char *key, const png_const_charp *text)
  {
     static char what[5] = { 116, 69, 88, 116, 0 };
     png_charp parameter_list[3];
  
     parameter_list[0] = strstash(key);
     parameter_list[1] = strstash_list(text);
     parameter_list[2] = NULL;
  
     return make_insert(what, insert_tEXt, 2, parameter_list);
  }
  
  static chunk_insert *
  add_iTXt(const char *key, const char *language, const char *language_key,
        const png_const_charp *text)
  {
     static char what[5] = { 105, 84, 88, 116, 0 };
     png_charp parameter_list[5];
  
     parameter_list[0] = strstash(key);
     parameter_list[1] = strstash(language);
     parameter_list[2] = strstash(language_key);
     parameter_list[3] = strstash_list(text);
     parameter_list[4] = NULL;
  
     return make_insert(what, insert_iTXt, 4, parameter_list);
  }
  
  /* This is a not-very-good parser for a sequence of numbers (including 0).  It
   * doesn't accept some apparently valid things, but it accepts all the sensible
   * combinations.
   */
  static void
  parse_color(char *arg, unsigned int *colors)
  {
     unsigned int ncolors = 0;
  
     while (*arg && ncolors < 4)
     {
        char *ep = arg;
  
        unsigned long ul = strtoul(arg, &ep, 0);
  
        if (ul > 65535)
        {
           fprintf(stderr, "makepng --color=...'%s': too big\n", arg);
           exit(1);
        }
  
        if (ep == arg)
        {
           fprintf(stderr, "makepng --color=...'%s': not a valid color\n", arg);
           exit(1);
        }
  
        if (*ep) ++ep; /* skip a separator */
        arg = ep;
  
        colors[++ncolors] = (unsigned int)ul; /* checked above */
     }
  
     if (*arg)
     {
        fprintf(stderr, "makepng --color=...'%s': too many values\n", arg);
        exit(1);
     }
  
     *colors = ncolors;
  }
  
  int
  main(int argc, char **argv)
  {
     FILE *fp = stdout;
     const char *file_name = NULL;
     int color_type = 8; /* invalid */
     int bit_depth = 32; /* invalid */
     int small = 0; /* make full size images */
     int tRNS = 0; /* don't output a tRNS chunk */
     unsigned int colors[5];
     unsigned int filters = PNG_ALL_FILTERS;
     png_fixed_point gamma = 0; /* not set */
     chunk_insert *head_insert = NULL;
     chunk_insert **insert_ptr = &head_insert;
  
     memset(colors, 0, sizeof colors);
  
     while (--argc > 0)
     {
        char *arg = *++argv;
  
        if (strcmp(arg, "--small") == 0)
        {
           small = 1;
           continue;
        }
  
        if (strcmp(arg, "--tRNS") == 0)
        {
           tRNS = 1;
           continue;
        }
  
        if (strcmp(arg, "--sRGB") == 0)
        {
           gamma = PNG_DEFAULT_sRGB;
           continue;
        }
  
        if (strcmp(arg, "--linear") == 0)
        {
           gamma = PNG_FP_1;
           continue;
        }
  
        if (strcmp(arg, "--1.8") == 0)
        {
           gamma = PNG_GAMMA_MAC_18;
           continue;
        }
  
        if (strcmp(arg, "--nofilters") == 0)
        {
           filters = PNG_FILTER_NONE;
           continue;
        }
  
        if (strncmp(arg, "--color=", 8) == 0)
        {
            parse_color(arg+8, colors);
            continue;
        }
  
        if (argc >= 3 && strcmp(arg, "--insert") == 0)
        {
           png_const_charp what = *++argv;
           png_charp param = *++argv;
           chunk_insert *new_insert;
  
           argc -= 2;
  
           new_insert = find_insert(what, param);
  
           if (new_insert != NULL)
           {
              *insert_ptr = new_insert;
              insert_ptr = &new_insert->next;
           }
  
           continue;
        }
  
        if (arg[0] == '-')
        {
           fprintf(stderr, "makepng: %s: invalid option\n", arg);
           exit(1);
        }
  
        if (strcmp(arg, "palette") == 0)
        {
           color_type = PNG_COLOR_TYPE_PALETTE;
           continue;
        }
  
        if (strncmp(arg, "gray", 4) == 0)
        {
           if (arg[4] == 0)
           {
              color_type = PNG_COLOR_TYPE_GRAY;
              continue;
           }
  
           else if (strcmp(arg+4, "a") == 0 ||
              strcmp(arg+4, "alpha") == 0 ||
              strcmp(arg+4, "-alpha") == 0)
           {
              color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
              continue;
           }
        }
  
        if (strncmp(arg, "rgb", 3) == 0)
        {
           if (arg[3] == 0)
           {
              color_type = PNG_COLOR_TYPE_RGB;
              continue;
           }
  
           else if (strcmp(arg+3, "a") == 0 ||
              strcmp(arg+3, "alpha") == 0 ||
              strcmp(arg+3, "-alpha") == 0)
           {
              color_type = PNG_COLOR_TYPE_RGB_ALPHA;
              continue;
           }
        }
  
        if (color_type == 8 && isdigit(arg[0]))
        {
           color_type = atoi(arg);
           if (color_type < 0 || color_type > 6 || color_type == 1 ||
              color_type == 5)
           {
              fprintf(stderr, "makepng: %s: not a valid color type\n", arg);
              exit(1);
           }
  
           continue;
        }
  
        if (bit_depth == 32 && isdigit(arg[0]))
        {
           bit_depth = atoi(arg);
           if (bit_depth <= 0 || bit_depth > 16 ||
              (bit_depth & -bit_depth) != bit_depth)
           {
              fprintf(stderr, "makepng: %s: not a valid bit depth\n", arg);
              exit(1);
           }
  
           continue;
        }
  
        if (argc == 1) /* It's the file name */
        {
           fp = fopen(arg, "wb");
           if (fp == NULL)
           {
              fprintf(stderr, "%s: %s: could not open\n", arg, strerror(errno));
              exit(1);
           }
  
           file_name = arg;
           continue;
        }
  
        fprintf(stderr, "makepng: %s: unknown argument\n", arg);
        exit(1);
     } /* argument while loop */
  
     if (color_type == 8 || bit_depth == 32)
     {
        fprintf(stderr, "usage: makepng [--small] [--sRGB|--linear|--1.8] "
           "[--color=...] color-type bit-depth [file-name]\n"
           "  Make a test PNG file, by default writes to stdout.\n"
           "  Other options are available, UTSL.\n");
        exit(1);
     }
  
     /* Check the colors */
     {
        unsigned int lim = (color_type == PNG_COLOR_TYPE_PALETTE ? 255U :
           (1U<<bit_depth)-1);
        unsigned int i;
  
        for (i=1; i<=colors[0]; ++i)
           if (colors[i] > lim)
           {
              fprintf(stderr, "makepng: --color=...: %u out of range [0..%u]\n",
                 colors[i], lim);
              exit(1);
           }
     }
  
     /* small and colors are incomparible (will probably crash if both are used at
      * the same time!)
      */
     if (small && colors[0] != 0)
     {
        fprintf(stderr, "makepng: --color --small: only one at a time!\n");
        exit(1);
     }
  
     /* Restrict the filters for more speed to those we know are used for the
      * generated images.
      */
     if (filters == PNG_ALL_FILTERS && !small/*small provides defaults*/)
     {
        if ((color_type & PNG_COLOR_MASK_PALETTE) != 0 || bit_depth < 8)
           filters = PNG_FILTER_NONE;
  
        else if (color_type & PNG_COLOR_MASK_COLOR) /* rgb */
        {
           if (bit_depth == 8)
              filters &= ~(PNG_FILTER_NONE | PNG_FILTER_AVG);
  
           else
              filters = PNG_FILTER_SUB | PNG_FILTER_PAETH;
        }
  
        else /* gray 8 or 16-bit */
           filters &= ~PNG_FILTER_NONE;
     }
  
     /* Insert standard copyright and licence text. */
     {
        static png_const_charp copyright[] =
        {
           COPYRIGHT, /* ISO-Latin-1 */
           NULL
        };
        static png_const_charp licensing[] =
        {
           IMAGE_LICENSING, /* UTF-8 */
           NULL
        };
  
        chunk_insert *new_insert;
  
        new_insert = add_tEXt("Copyright", copyright);
        if (new_insert != NULL)
        {
           *insert_ptr = new_insert;
           insert_ptr = &new_insert->next;
        }
  
        new_insert = add_iTXt("Licensing", "en", NULL, licensing);
        if (new_insert != NULL)
        {
           *insert_ptr = new_insert;
           insert_ptr = &new_insert->next;
        }
     }
  
     {
        int ret = write_png(&file_name, fp, color_type, bit_depth, gamma,
           head_insert, filters, colors, small, tRNS);
  
        if (ret != 0 && file_name != NULL)
           remove(file_name);
  
        return ret;
     }
  }
  