text: /*
   * Copyright 2015 The Android Open Source Project
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #ifndef SkCodecPriv_DEFINED
  #define SkCodecPriv_DEFINED
  
  #include "SkColorPriv.h"
  #include "SkColorTable.h"
  #include "SkImageInfo.h"
  #include "SkTypes.h"
  
  #ifdef SK_PRINT_CODEC_MESSAGES
      #define SkCodecPrintf SkDebugf
  #else
      #define SkCodecPrintf(...)
  #endif
  
  // FIXME: Consider sharing with dm, nanbench, and tools.
  static inline float get_scale_from_sample_size(int sampleSize) {
      return 1.0f / ((float) sampleSize);
  }
  
  static inline bool is_valid_subset(const SkIRect& subset, const SkISize& imageDims) {
      return SkIRect::MakeSize(imageDims).contains(subset);
  }
  
  /*
   * returns a scaled dimension based on the original dimension and the sampleSize
   * NOTE: we round down here for scaled dimension to match the behavior of SkImageDecoder
   * FIXME: I think we should call this get_sampled_dimension().
   */
  static inline int get_scaled_dimension(int srcDimension, int sampleSize) {
      if (sampleSize > srcDimension) {
          return 1;
      }
      return srcDimension / sampleSize;
  }
  
  /*
   * Returns the first coordinate that we will keep during a scaled decode.
   * The output can be interpreted as an x-coordinate or a y-coordinate.
   *
   * This does not need to be called and is not called when sampleFactor == 1.
   */
  static inline int get_start_coord(int sampleFactor) { return sampleFactor / 2; };
  
  /*
   * Given a coordinate in the original image, this returns the corresponding
   * coordinate in the scaled image.  This function is meaningless if
   * IsCoordNecessary returns false.
   * The output can be interpreted as an x-coordinate or a y-coordinate.
   *
   * This does not need to be called and is not called when sampleFactor == 1.
   */
  static inline int get_dst_coord(int srcCoord, int sampleFactor) { return srcCoord / sampleFactor; };
  
  /*
   * When scaling, we will discard certain y-coordinates (rows) and
   * x-coordinates (columns).  This function returns true if we should keep the
   * coordinate and false otherwise.
   * The inputs may be x-coordinates or y-coordinates.
   *
   * This does not need to be called and is not called when sampleFactor == 1.
   */
  static inline bool is_coord_necessary(int srcCoord, int sampleFactor, int scaledDim) {
      // Get the first coordinate that we want to keep
      int startCoord = get_start_coord(sampleFactor);
  
      // Return false on edge cases
      if (srcCoord < startCoord || get_dst_coord(srcCoord, sampleFactor) >= scaledDim) {
          return false;
      }
  
      // Every sampleFactor rows are necessary
      return ((srcCoord - startCoord) % sampleFactor) == 0;
  }
  
  static inline bool valid_alpha(SkAlphaType dstAlpha, SkAlphaType srcAlpha) {
      if (kUnknown_SkAlphaType == dstAlpha) {
          return false;
      }
  
      if (srcAlpha != dstAlpha) {
          if (kOpaque_SkAlphaType == srcAlpha) {
              // If the source is opaque, we can support any.
              SkCodecPrintf("Warning: an opaque image should be decoded as opaque "
                            "- it is being decoded as non-opaque, which will draw slower\n");
              return true;
          }
  
          // The source is not opaque
          switch (dstAlpha) {
              case kPremul_SkAlphaType:
              case kUnpremul_SkAlphaType:
                  // The source is not opaque, so either of these is okay
                  break;
              default:
                  // We cannot decode a non-opaque image to opaque (or unknown)
                  return false;
          }
      }
      return true;
  }
  
  /*
   * Most of our codecs support the same conversions:
   * - opaque to any alpha type
   * - 565 only if opaque
   * - premul to unpremul and vice versa
   * - always support N32
   * - otherwise match the src color type
   */
  static inline bool conversion_possible(const SkImageInfo& dst, const SkImageInfo& src) {
      // Ensure the alpha type is valid
      if (!valid_alpha(dst.alphaType(), src.alphaType())) {
          return false;
      }
  
      // Check for supported color types
      switch (dst.colorType()) {
          case kRGBA_8888_SkColorType:
          case kBGRA_8888_SkColorType:
              return true;
          case kRGB_565_SkColorType:
              return kOpaque_SkAlphaType == src.alphaType();
          default:
              return dst.colorType() == src.colorType();
      }
  }
  
  /*
   * If there is a color table, get a pointer to the colors, otherwise return nullptr
   */
  static inline const SkPMColor* get_color_ptr(SkColorTable* colorTable) {
       return nullptr != colorTable ? colorTable->readColors() : nullptr;
  }
  
  /*
   * Given that the encoded image uses a color table, return the fill value
   */
  static inline uint32_t get_color_table_fill_value(SkColorType colorType, const SkPMColor* colorPtr,
          uint8_t fillIndex) {
      SkASSERT(nullptr != colorPtr);
      switch (colorType) {
          case kRGBA_8888_SkColorType:
          case kBGRA_8888_SkColorType:
              return colorPtr[fillIndex];
          case kRGB_565_SkColorType:
              return SkPixel32ToPixel16(colorPtr[fillIndex]);
          case kIndex_8_SkColorType:
              return fillIndex;
          default:
              SkASSERT(false);
              return 0;
      }
  }
  
  /*
   *
   * Copy the codec color table back to the client when kIndex8 color type is requested
   */
  static inline void copy_color_table(const SkImageInfo& dstInfo, SkColorTable* colorTable,
          SkPMColor* inputColorPtr, int* inputColorCount) {
      if (kIndex_8_SkColorType == dstInfo.colorType()) {
          SkASSERT(nullptr != inputColorPtr);
          SkASSERT(nullptr != inputColorCount);
          SkASSERT(nullptr != colorTable);
          memcpy(inputColorPtr, colorTable->readColors(), *inputColorCount * sizeof(SkPMColor));
      }
  }
  
  /*
   * Compute row bytes for an image using pixels per byte
   */
  static inline size_t compute_row_bytes_ppb(int width, uint32_t pixelsPerByte) {
      return (width + pixelsPerByte - 1) / pixelsPerByte;
  }
  
  /*
   * Compute row bytes for an image using bytes per pixel
   */
  static inline size_t compute_row_bytes_bpp(int width, uint32_t bytesPerPixel) {
      return width * bytesPerPixel;
  }
  
  /*
   * Compute row bytes for an image
   */
  static inline size_t compute_row_bytes(int width, uint32_t bitsPerPixel) {
      if (bitsPerPixel < 16) {
          SkASSERT(0 == 8 % bitsPerPixel);
          const uint32_t pixelsPerByte = 8 / bitsPerPixel;
          return compute_row_bytes_ppb(width, pixelsPerByte);
      } else {
          SkASSERT(0 == bitsPerPixel % 8);
          const uint32_t bytesPerPixel = bitsPerPixel / 8;
          return compute_row_bytes_bpp(width, bytesPerPixel);
      }
  }
  
  /*
   * Get a byte from a buffer
   * This method is unsafe, the caller is responsible for performing a check
   */
  static inline uint8_t get_byte(uint8_t* buffer, uint32_t i) {
      return buffer[i];
  }
  
  /*
   * Get a short from a buffer
   * This method is unsafe, the caller is responsible for performing a check
   */
  static inline uint16_t get_short(uint8_t* buffer, uint32_t i) {
      uint16_t result;
      memcpy(&result, &(buffer[i]), 2);
  #ifdef SK_CPU_BENDIAN
      return SkEndianSwap16(result);
  #else
      return result;
  #endif
  }
  
  /*
   * Get an int from a buffer
   * This method is unsafe, the caller is responsible for performing a check
   */
  static inline uint32_t get_int(uint8_t* buffer, uint32_t i) {
      uint32_t result;
      memcpy(&result, &(buffer[i]), 4);
  #ifdef SK_CPU_BENDIAN
      return SkEndianSwap32(result);
  #else
      return result;
  #endif
  }
  
  /*
   * @param data           Buffer to read bytes from
   * @param isLittleEndian Output parameter
   *                       Indicates if the data is little endian
   *                       Is unaffected on false returns
   */
  static inline bool is_valid_endian_marker(const uint8_t* data, bool* isLittleEndian) {
      // II indicates Intel (little endian) and MM indicates motorola (big endian).
      if (('I' != data[0] || 'I' != data[1]) && ('M' != data[0] || 'M' != data[1])) {
          return false;
      }
  
      *isLittleEndian = ('I' == data[0]);
      return true;
  }
  
  static inline uint16_t get_endian_short(const uint8_t* data, bool littleEndian) {
      if (littleEndian) {
          return (data[1] << 8) | (data[0]);
      }
  
      return (data[0] << 8) | (data[1]);
  }
  
  static inline SkPMColor premultiply_argb_as_rgba(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
      if (a != 255) {
          r = SkMulDiv255Round(r, a);
          g = SkMulDiv255Round(g, a);
          b = SkMulDiv255Round(b, a);
      }
  
      return SkPackARGB_as_RGBA(a, r, g, b);
  }
  
  static inline SkPMColor premultiply_argb_as_bgra(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
      if (a != 255) {
          r = SkMulDiv255Round(r, a);
          g = SkMulDiv255Round(g, a);
          b = SkMulDiv255Round(b, a);
      }
  
      return SkPackARGB_as_BGRA(a, r, g, b);
  }
  
  static inline bool is_rgba(SkColorType colorType) {
  #ifdef SK_PMCOLOR_IS_RGBA
      return (kBGRA_8888_SkColorType != colorType);
  #else
      return (kRGBA_8888_SkColorType == colorType);
  #endif
  }
  
  // Method for coverting to a 32 bit pixel.
  typedef uint32_t (*PackColorProc)(U8CPU a, U8CPU r, U8CPU g, U8CPU b);
  
  static inline PackColorProc choose_pack_color_proc(bool isPremul, SkColorType colorType) {
      bool isRGBA = is_rgba(colorType);
      if (isPremul) {
          if (isRGBA) {
              return &premultiply_argb_as_rgba;
          } else {
              return &premultiply_argb_as_bgra;
          }
      } else {
          if (isRGBA) {
              return &SkPackARGB_as_RGBA;
          } else {
              return &SkPackARGB_as_BGRA;
          }
      }
  }
  
  static inline bool needs_color_xform(const SkImageInfo& dstInfo, const SkImageInfo& srcInfo) {
      return (kRGBA_F16_SkColorType == dstInfo.colorType()) ||
             (dstInfo.colorSpace() && !SkColorSpace::Equals(srcInfo.colorSpace(),
                                                            dstInfo.colorSpace()));
  }
  
  #endif // SkCodecPriv_DEFINED
  