text: /*
   * Copyright (c) 2014 Clément Bœsch
   *
   * This file is part of FFmpeg.
   *
   * Permission to use, copy, modify, and/or distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  /**
   * @file
   * hqx magnification filters (hq2x, hq3x, hq4x)
   *
   * Originally designed by Maxim Stephin.
   *
   * @see http://en.wikipedia.org/wiki/Hqx
   * @see http://web.archive.org/web/20131114143602/http://www.hiend3d.com/hq3x.html
   * @see http://blog.pkh.me/p/19-butchering-hqx-scaling-filters.html
   */
  
  #include "libavutil/opt.h"
  #include "libavutil/avassert.h"
  #include "libavutil/pixdesc.h"
  #include "internal.h"
  
  typedef int (*hqxfunc_t)(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs);
  
  typedef struct {
      const AVClass *class;
      int n;
      hqxfunc_t func;
      uint32_t rgbtoyuv[1<<24];
  } HQXContext;
  
  typedef struct ThreadData {
      AVFrame *in, *out;
      const uint32_t *rgbtoyuv;
  } ThreadData;
  
  #define OFFSET(x) offsetof(HQXContext, x)
  #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
  static const AVOption hqx_options[] = {
      { "n", "set scale factor", OFFSET(n), AV_OPT_TYPE_INT, {.i64 = 3}, 2, 4, .flags = FLAGS },
      { NULL }
  };
  
  AVFILTER_DEFINE_CLASS(hqx);
  
  static av_always_inline uint32_t rgb2yuv(const uint32_t *r2y, uint32_t c)
  {
      return r2y[c & 0xffffff];
  }
  
  static av_always_inline int yuv_diff(uint32_t yuv1, uint32_t yuv2)
  {
  #define YMASK 0xff0000
  #define UMASK 0x00ff00
  #define VMASK 0x0000ff
  #define ABSDIFF(a,b) (abs((int)(a)-(int)(b)))
  
      return ABSDIFF(yuv1 & YMASK, yuv2 & YMASK) > (48 << 16) ||
             ABSDIFF(yuv1 & UMASK, yuv2 & UMASK) > ( 7 <<  8) ||
             ABSDIFF(yuv1 & VMASK, yuv2 & VMASK) > ( 6 <<  0);
  }
  
  /* (c1*w1 + c2*w2) >> s */
  static av_always_inline uint32_t interp_2px(uint32_t c1, int w1, uint32_t c2, int w2, int s)
  {
      return (((((c1 & 0xff00ff00) >> 8) * w1 + ((c2 & 0xff00ff00) >> 8) * w2) << (8 - s)) & 0xff00ff00) |
             (((((c1 & 0x00ff00ff)     ) * w1 + ((c2 & 0x00ff00ff)     ) * w2) >>      s ) & 0x00ff00ff);
  }
  
  /* (c1*w1 + c2*w2 + c3*w3) >> s */
  static av_always_inline uint32_t interp_3px(uint32_t c1, int w1, uint32_t c2, int w2, uint32_t c3, int w3, int s)
  {
      return (((((c1 & 0xff00ff00) >> 8) * w1 + ((c2 & 0xff00ff00) >> 8) * w2 + ((c3 & 0xff00ff00) >> 8) * w3) << (8 - s)) & 0xff00ff00) |
             (((((c1 & 0x00ff00ff)     ) * w1 + ((c2 & 0x00ff00ff)     ) * w2 + ((c3 & 0x00ff00ff)     ) * w3) >>      s ) & 0x00ff00ff);
  }
  
  /* m is the mask of diff with the center pixel that matters in the pattern, and
   * r is the expected result (bit set to 1 if there is difference with the
   * center, 0 otherwise) */
  #define P(m, r) ((k_shuffled & (m)) == (r))
  
  /* adjust 012345678 to 01235678: the mask doesn't contain the (null) diff
   * between the center/current pixel and itself */
  #define DROP4(z) ((z) > 4 ? (z)-1 : (z))
  
  /* shuffle the input mask: move bit n (4-adjusted) to position stored in p<n> */
  #define SHF(x, rot, n) (((x) >> ((rot) ? 7-DROP4(n) : DROP4(n)) & 1) << DROP4(p##n))
  
  /* used to check if there is YUV difference between 2 pixels */
  #define WDIFF(c1, c2) yuv_diff(rgb2yuv(r2y, c1), rgb2yuv(r2y, c2))
  
  /* bootstrap template for every interpolation code. It defines the shuffled
   * masks and surrounding pixels. The rot flag is used to indicate if it's a
   * rotation; its basic effect is to shuffle k using p8..p0 instead of p0..p8 */
  #define INTERP_BOOTSTRAP(rot)                                           \
      const int k_shuffled = SHF(k,rot,0) | SHF(k,rot,1) | SHF(k,rot,2)   \
                           | SHF(k,rot,3) |       0      | SHF(k,rot,5)   \
                           | SHF(k,rot,6) | SHF(k,rot,7) | SHF(k,rot,8);  \
                                                                          \
      const uint32_t w0 = w[p0], w1 = w[p1],                              \
                     w3 = w[p3], w4 = w[p4], w5 = w[p5],                  \
                                 w7 = w[p7]
  
  /* Assuming p0..p8 is mapped to pixels 0..8, this function interpolates the
   * top-left pixel in the total of the 2x2 pixels to interpolates. The function
   * is also used for the 3 other pixels */
  static av_always_inline uint32_t hq2x_interp_1x1(const uint32_t *r2y, int k,
                                                   const uint32_t *w,
                                                   int p0, int p1, int p2,
                                                   int p3, int p4, int p5,
                                                   int p6, int p7, int p8)
  {
      INTERP_BOOTSTRAP(0);
  
      if ((P(0xbf,0x37) || P(0xdb,0x13)) && WDIFF(w1, w5))
          return interp_2px(w4, 3, w3, 1, 2);
      if ((P(0xdb,0x49) || P(0xef,0x6d)) && WDIFF(w7, w3))
          return interp_2px(w4, 3, w1, 1, 2);
      if ((P(0x0b,0x0b) || P(0xfe,0x4a) || P(0xfe,0x1a)) && WDIFF(w3, w1))
          return w4;
      if ((P(0x6f,0x2a) || P(0x5b,0x0a) || P(0xbf,0x3a) || P(0xdf,0x5a) ||
           P(0x9f,0x8a) || P(0xcf,0x8a) || P(0xef,0x4e) || P(0x3f,0x0e) ||
           P(0xfb,0x5a) || P(0xbb,0x8a) || P(0x7f,0x5a) || P(0xaf,0x8a) ||
           P(0xeb,0x8a)) && WDIFF(w3, w1))
          return interp_2px(w4, 3, w0, 1, 2);
      if (P(0x0b,0x08))
          return interp_3px(w4, 2, w0, 1, w1, 1, 2);
      if (P(0x0b,0x02))
          return interp_3px(w4, 2, w0, 1, w3, 1, 2);
      if (P(0x2f,0x2f))
          return interp_3px(w4, 14, w3, 1, w1, 1, 4);
      if (P(0xbf,0x37) || P(0xdb,0x13))
          return interp_3px(w4, 5, w1, 2, w3, 1, 3);
      if (P(0xdb,0x49) || P(0xef,0x6d))
          return interp_3px(w4, 5, w3, 2, w1, 1, 3);
      if (P(0x1b,0x03) || P(0x4f,0x43) || P(0x8b,0x83) || P(0x6b,0x43))
          return interp_2px(w4, 3, w3, 1, 2);
      if (P(0x4b,0x09) || P(0x8b,0x89) || P(0x1f,0x19) || P(0x3b,0x19))
          return interp_2px(w4, 3, w1, 1, 2);
      if (P(0x7e,0x2a) || P(0xef,0xab) || P(0xbf,0x8f) || P(0x7e,0x0e))
          return interp_3px(w4, 2, w3, 3, w1, 3, 3);
      if (P(0xfb,0x6a) || P(0x6f,0x6e) || P(0x3f,0x3e) || P(0xfb,0xfa) ||
          P(0xdf,0xde) || P(0xdf,0x1e))
          return interp_2px(w4, 3, w0, 1, 2);
      if (P(0x0a,0x00) || P(0x4f,0x4b) || P(0x9f,0x1b) || P(0x2f,0x0b) ||
          P(0xbe,0x0a) || P(0xee,0x0a) || P(0x7e,0x0a) || P(0xeb,0x4b) ||
          P(0x3b,0x1b))
          return interp_3px(w4, 2, w3, 1, w1, 1, 2);
      return interp_3px(w4, 6, w3, 1, w1, 1, 3);
  }
  
  /* Assuming p0..p8 is mapped to pixels 0..8, this function interpolates the
   * top-left and top-center pixel in the total of the 3x3 pixels to
   * interpolates. The function is also used for the 3 other couples of pixels
   * defining the outline. The center pixel is not defined through this function,
   * since it's just the same as the original value. */
  static av_always_inline void hq3x_interp_2x1(uint32_t *dst, int dst_linesize,
                                               const uint32_t *r2y, int k,
                                               const uint32_t *w,
                                               int pos00, int pos01,
                                               int p0, int p1, int p2,
                                               int p3, int p4, int p5,
                                               int p6, int p7, int p8,
                                               int rotate)
  {
      INTERP_BOOTSTRAP(rotate);
  
      uint32_t *dst00 = &dst[dst_linesize*(pos00>>1) + (pos00&1)];
      uint32_t *dst01 = &dst[dst_linesize*(pos01>>1) + (pos01&1)];
  
      if ((P(0xdb,0x49) || P(0xef,0x6d)) && WDIFF(w7, w3))
          *dst00 = interp_2px(w4, 3, w1, 1, 2);
      else if ((P(0xbf,0x37) || P(0xdb,0x13)) && WDIFF(w1, w5))
          *dst00 = interp_2px(w4, 3, w3, 1, 2);
      else if ((P(0x0b,0x0b) || P(0xfe,0x4a) || P(0xfe,0x1a)) && WDIFF(w3, w1))
          *dst00 = w4;
      else if ((P(0x6f,0x2a) || P(0x5b,0x0a) || P(0xbf,0x3a) || P(0xdf,0x5a) ||
                P(0x9f,0x8a) || P(0xcf,0x8a) || P(0xef,0x4e) || P(0x3f,0x0e) ||
                P(0xfb,0x5a) || P(0xbb,0x8a) || P(0x7f,0x5a) || P(0xaf,0x8a) ||
                P(0xeb,0x8a)) && WDIFF(w3, w1))
          *dst00 = interp_2px(w4, 3, w0, 1, 2);
      else if (P(0x4b,0x09) || P(0x8b,0x89) || P(0x1f,0x19) || P(0x3b,0x19))
          *dst00 = interp_2px(w4, 3, w1, 1, 2);
      else if (P(0x1b,0x03) || P(0x4f,0x43) || P(0x8b,0x83) || P(0x6b,0x43))
          *dst00 = interp_2px(w4, 3, w3, 1, 2);
      else if (P(0x7e,0x2a) || P(0xef,0xab) || P(0xbf,0x8f) || P(0x7e,0x0e))
          *dst00 = interp_2px(w3, 1, w1, 1, 1);
      else if (P(0x4f,0x4b) || P(0x9f,0x1b) || P(0x2f,0x0b) || P(0xbe,0x0a) ||
               P(0xee,0x0a) || P(0x7e,0x0a) || P(0xeb,0x4b) || P(0x3b,0x1b))
          *dst00 = interp_3px(w4, 2, w3, 7, w1, 7, 4);
      else if (P(0x0b,0x08) || P(0xf9,0x68) || P(0xf3,0x62) || P(0x6d,0x6c) ||
               P(0x67,0x66) || P(0x3d,0x3c) || P(0x37,0x36) || P(0xf9,0xf8) ||
               P(0xdd,0xdc) || P(0xf3,0xf2) || P(0xd7,0xd6) || P(0xdd,0x1c) ||
               P(0xd7,0x16) || P(0x0b,0x02))
          *dst00 = interp_2px(w4, 3, w0, 1, 2);
      else
          *dst00 = interp_3px(w4, 2, w3, 1, w1, 1, 2);
  
      if ((P(0xfe,0xde) || P(0x9e,0x16) || P(0xda,0x12) || P(0x17,0x16) ||
           P(0x5b,0x12) || P(0xbb,0x12)) && WDIFF(w1, w5))
          *dst01 = w4;
      else if ((P(0x0f,0x0b) || P(0x5e,0x0a) || P(0xfb,0x7b) || P(0x3b,0x0b) ||
                P(0xbe,0x0a) || P(0x7a,0x0a)) && WDIFF(w3, w1))
          *dst01 = w4;
      else if (P(0xbf,0x8f) || P(0x7e,0x0e) || P(0xbf,0x37) || P(0xdb,0x13))
          *dst01 = interp_2px(w1, 3, w4, 1, 2);
      else if (P(0x02,0x00) || P(0x7c,0x28) || P(0xed,0xa9) || P(0xf5,0xb4) ||
               P(0xd9,0x90))
          *dst01 = interp_2px(w4, 3, w1, 1, 2);
      else if (P(0x4f,0x4b) || P(0xfb,0x7b) || P(0xfe,0x7e) || P(0x9f,0x1b) ||
               P(0x2f,0x0b) || P(0xbe,0x0a) || P(0x7e,0x0a) || P(0xfb,0x4b) ||
               P(0xfb,0xdb) || P(0xfe,0xde) || P(0xfe,0x56) || P(0x57,0x56) ||
               P(0x97,0x16) || P(0x3f,0x1e) || P(0xdb,0x12) || P(0xbb,0x12))
          *dst01 = interp_2px(w4, 7, w1, 1, 3);
      else
          *dst01 = w4;
  }
  
  /* Assuming p0..p8 is mapped to pixels 0..8, this function interpolates the
   * top-left block of 2x2 pixels in the total of the 4x4 pixels (or 4 blocks) to
   * interpolates. The function is also used for the 3 other blocks of 2x2
   * pixels. */
  static av_always_inline void hq4x_interp_2x2(uint32_t *dst, int dst_linesize,
                                               const uint32_t *r2y, int k,
                                               const uint32_t *w,
                                               int pos00, int pos01,
                                               int pos10, int pos11,
                                               int p0, int p1, int p2,
                                               int p3, int p4, int p5,
                                               int p6, int p7, int p8)
  {
      INTERP_BOOTSTRAP(0);
  
      uint32_t *dst00 = &dst[dst_linesize*(pos00>>1) + (pos00&1)];
      uint32_t *dst01 = &dst[dst_linesize*(pos01>>1) + (pos01&1)];
      uint32_t *dst10 = &dst[dst_linesize*(pos10>>1) + (pos10&1)];
      uint32_t *dst11 = &dst[dst_linesize*(pos11>>1) + (pos11&1)];
  
      const int cond00 = (P(0xbf,0x37) || P(0xdb,0x13)) && WDIFF(w1, w5);
      const int cond01 = (P(0xdb,0x49) || P(0xef,0x6d)) && WDIFF(w7, w3);
      const int cond02 = (P(0x6f,0x2a) || P(0x5b,0x0a) || P(0xbf,0x3a) ||
                          P(0xdf,0x5a) || P(0x9f,0x8a) || P(0xcf,0x8a) ||
                          P(0xef,0x4e) || P(0x3f,0x0e) || P(0xfb,0x5a) ||
                          P(0xbb,0x8a) || P(0x7f,0x5a) || P(0xaf,0x8a) ||
                          P(0xeb,0x8a)) && WDIFF(w3, w1);
      const int cond03 = P(0xdb,0x49) || P(0xef,0x6d);
      const int cond04 = P(0xbf,0x37) || P(0xdb,0x13);
      const int cond05 = P(0x1b,0x03) || P(0x4f,0x43) || P(0x8b,0x83) ||
                         P(0x6b,0x43);
      const int cond06 = P(0x4b,0x09) || P(0x8b,0x89) || P(0x1f,0x19) ||
                         P(0x3b,0x19);
      const int cond07 = P(0x0b,0x08) || P(0xf9,0x68) || P(0xf3,0x62) ||
                         P(0x6d,0x6c) || P(0x67,0x66) || P(0x3d,0x3c) ||
                         P(0x37,0x36) || P(0xf9,0xf8) || P(0xdd,0xdc) ||
                         P(0xf3,0xf2) || P(0xd7,0xd6) || P(0xdd,0x1c) ||
                         P(0xd7,0x16) || P(0x0b,0x02);
      const int cond08 = (P(0x0f,0x0b) || P(0x2b,0x0b) || P(0xfe,0x4a) ||
                          P(0xfe,0x1a)) && WDIFF(w3, w1);
      const int cond09 = P(0x2f,0x2f);
      const int cond10 = P(0x0a,0x00);
      const int cond11 = P(0x0b,0x09);
      const int cond12 = P(0x7e,0x2a) || P(0xef,0xab);
      const int cond13 = P(0xbf,0x8f) || P(0x7e,0x0e);
      const int cond14 = P(0x4f,0x4b) || P(0x9f,0x1b) || P(0x2f,0x0b) ||
                         P(0xbe,0x0a) || P(0xee,0x0a) || P(0x7e,0x0a) ||
                         P(0xeb,0x4b) || P(0x3b,0x1b);
      const int cond15 = P(0x0b,0x03);
  
      if (cond00)
          *dst00 = interp_2px(w4, 5, w3, 3, 3);
      else if (cond01)
          *dst00 = interp_2px(w4, 5, w1, 3, 3);
      else if ((P(0x0b,0x0b) || P(0xfe,0x4a) || P(0xfe,0x1a)) && WDIFF(w3, w1))
          *dst00 = w4;
      else if (cond02)
          *dst00 = interp_2px(w4, 5, w0, 3, 3);
      else if (cond03)
          *dst00 = interp_2px(w4, 3, w3, 1, 2);
      else if (cond04)
          *dst00 = interp_2px(w4, 3, w1, 1, 2);
      else if (cond05)
          *dst00 = interp_2px(w4, 5, w3, 3, 3);
      else if (cond06)
          *dst00 = interp_2px(w4, 5, w1, 3, 3);
      else if (P(0x0f,0x0b) || P(0x5e,0x0a) || P(0x2b,0x0b) || P(0xbe,0x0a) ||
               P(0x7a,0x0a) || P(0xee,0x0a))
          *dst00 = interp_2px(w1, 1, w3, 1, 1);
      else if (cond07)
          *dst00 = interp_2px(w4, 5, w0, 3, 3);
      else
          *dst00 = interp_3px(w4, 2, w1, 1, w3, 1, 2);
  
      if (cond00)
          *dst01 = interp_2px(w4, 7, w3, 1, 3);
      else if (cond08)
          *dst01 = w4;
      else if (cond02)
          *dst01 = interp_2px(w4, 3, w0, 1, 2);
      else if (cond09)
          *dst01 = w4;
      else if (cond10)
          *dst01 = interp_3px(w4, 5, w1, 2, w3, 1, 3);
      else if (P(0x0b,0x08))
          *dst01 = interp_3px(w4, 5, w1, 2, w0, 1, 3);
      else if (cond11)
          *dst01 = interp_2px(w4, 5, w1, 3, 3);
      else if (cond04)
          *dst01 = interp_2px(w1, 3, w4, 1, 2);
      else if (cond12)
          *dst01 = interp_3px(w1, 2, w4, 1, w3, 1, 2);
      else if (cond13)
          *dst01 = interp_2px(w1, 5, w3, 3, 3);
      else if (cond05)
          *dst01 = interp_2px(w4, 7, w3, 1, 3);
      else if (P(0xf3,0x62) || P(0x67,0x66) || P(0x37,0x36) || P(0xf3,0xf2) ||
               P(0xd7,0xd6) || P(0xd7,0x16) || P(0x0b,0x02))
          *dst01 = interp_2px(w4, 3, w0, 1, 2);
      else if (cond14)
          *dst01 = interp_2px(w1, 1, w4, 1, 1);
      else
          *dst01 = interp_2px(w4, 3, w1, 1, 2);
  
      if (cond01)
          *dst10 = interp_2px(w4, 7, w1, 1, 3);
      else if (cond08)
          *dst10 = w4;
      else if (cond02)
          *dst10 = interp_2px(w4, 3, w0, 1, 2);
      else if (cond09)
          *dst10 = w4;
      else if (cond10)
          *dst10 = interp_3px(w4, 5, w3, 2, w1, 1, 3);
      else if (P(0x0b,0x02))
          *dst10 = interp_3px(w4, 5, w3, 2, w0, 1, 3);
      else if (cond15)
          *dst10 = interp_2px(w4, 5, w3, 3, 3);
      else if (cond03)
          *dst10 = interp_2px(w3, 3, w4, 1, 2);
      else if (cond13)
          *dst10 = interp_3px(w3, 2, w4, 1, w1, 1, 2);
      else if (cond12)
          *dst10 = interp_2px(w3, 5, w1, 3, 3);
      else if (cond06)
          *dst10 = interp_2px(w4, 7, w1, 1, 3);
      else if (P(0x0b,0x08) || P(0xf9,0x68) || P(0x6d,0x6c) || P(0x3d,0x3c) ||
               P(0xf9,0xf8) || P(0xdd,0xdc) || P(0xdd,0x1c))
          *dst10 = interp_2px(w4, 3, w0, 1, 2);
      else if (cond14)
          *dst10 = interp_2px(w3, 1, w4, 1, 1);
      else
          *dst10 = interp_2px(w4, 3, w3, 1, 2);
  
      if ((P(0x7f,0x2b) || P(0xef,0xab) || P(0xbf,0x8f) || P(0x7f,0x0f)) &&
           WDIFF(w3, w1))
          *dst11 = w4;
      else if (cond02)
          *dst11 = interp_2px(w4, 7, w0, 1, 3);
      else if (cond15)
          *dst11 = interp_2px(w4, 7, w3, 1, 3);
      else if (cond11)
          *dst11 = interp_2px(w4, 7, w1, 1, 3);
      else if (P(0x0a,0x00) || P(0x7e,0x2a) || P(0xef,0xab) || P(0xbf,0x8f) ||
               P(0x7e,0x0e))
          *dst11 = interp_3px(w4, 6, w3, 1, w1, 1, 3);
      else if (cond07)
          *dst11 = interp_2px(w4, 7, w0, 1, 3);
      else
          *dst11 = w4;
  }
  
  static av_always_inline void hqx_filter(const ThreadData *td, int jobnr, int nb_jobs, int n)
  {
      int x, y;
      AVFrame *in = td->in, *out = td->out;
      const uint32_t *r2y = td->rgbtoyuv;
      const int height = in->height;
      const int width  = in->width;
      const int slice_start = (height *  jobnr   ) / nb_jobs;
      const int slice_end   = (height * (jobnr+1)) / nb_jobs;
      const int dst_linesize = out->linesize[0];
      const int src_linesize =  in->linesize[0];
      uint8_t       *dst = out->data[0] + slice_start * dst_linesize * n;
      const uint8_t *src =  in->data[0] + slice_start * src_linesize;
  
      const int dst32_linesize = dst_linesize >> 2;
      const int src32_linesize = src_linesize >> 2;
  
      for (y = slice_start; y < slice_end; y++) {
          const uint32_t *src32 = (const uint32_t *)src;
          uint32_t       *dst32 = (uint32_t *)dst;
          const int prevline = y > 0          ? -src32_linesize : 0;
          const int nextline = y < height - 1 ?  src32_linesize : 0;
  
          for (x = 0; x < width; x++) {
              const int prevcol = x > 0        ? -1 : 0;
              const int nextcol = x < width -1 ?  1 : 0;
              const uint32_t w[3*3] = {
                  src32[prevcol + prevline], src32[prevline], src32[prevline + nextcol],
                  src32[prevcol           ], src32[       0], src32[           nextcol],
                  src32[prevcol + nextline], src32[nextline], src32[nextline + nextcol]
              };
              const uint32_t yuv1 = rgb2yuv(r2y, w[4]);
              const int pattern = (w[4] != w[0] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[0]))) : 0)
                                | (w[4] != w[1] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[1]))) : 0) << 1
                                | (w[4] != w[2] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[2]))) : 0) << 2
                                | (w[4] != w[3] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[3]))) : 0) << 3
                                | (w[4] != w[5] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[5]))) : 0) << 4
                                | (w[4] != w[6] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[6]))) : 0) << 5
                                | (w[4] != w[7] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[7]))) : 0) << 6
                                | (w[4] != w[8] ? (yuv_diff(yuv1, rgb2yuv(r2y, w[8]))) : 0) << 7;
  
              if (n == 2) {
                  dst32[dst32_linesize*0 + 0] = hq2x_interp_1x1(r2y, pattern, w, 0,1,2,3,4,5,6,7,8);  // 00
                  dst32[dst32_linesize*0 + 1] = hq2x_interp_1x1(r2y, pattern, w, 2,1,0,5,4,3,8,7,6);  // 01 (vert mirrored)
                  dst32[dst32_linesize*1 + 0] = hq2x_interp_1x1(r2y, pattern, w, 6,7,8,3,4,5,0,1,2);  // 10 (horiz mirrored)
                  dst32[dst32_linesize*1 + 1] = hq2x_interp_1x1(r2y, pattern, w, 8,7,6,5,4,3,2,1,0);  // 11 (center mirrored)
              } else if (n == 3) {
                  hq3x_interp_2x1(dst32,                        dst32_linesize, r2y, pattern, w, 0,1, 0,1,2,3,4,5,6,7,8, 0);  // 00 01
                  hq3x_interp_2x1(dst32 + 1,                    dst32_linesize, r2y, pattern, w, 1,3, 2,5,8,1,4,7,0,3,6, 1);  // 02 12 (rotated to the right)
                  hq3x_interp_2x1(dst32 + 1*dst32_linesize,     dst32_linesize, r2y, pattern, w, 2,0, 6,3,0,7,4,1,8,5,2, 1);  // 20 10 (rotated to the left)
                  hq3x_interp_2x1(dst32 + 1*dst32_linesize + 1, dst32_linesize, r2y, pattern, w, 3,2, 8,7,6,5,4,3,2,1,0, 0);  // 22 21 (center mirrored)
                  dst32[dst32_linesize + 1] = w[4];                                                                           // 11
              } else if (n == 4) {
                  hq4x_interp_2x2(dst32,                        dst32_linesize, r2y, pattern, w, 0,1,2,3, 0,1,2,3,4,5,6,7,8); // 00 01 10 11
                  hq4x_interp_2x2(dst32 + 2,                    dst32_linesize, r2y, pattern, w, 1,0,3,2, 2,1,0,5,4,3,8,7,6); // 02 03 12 13 (vert mirrored)
                  hq4x_interp_2x2(dst32 + 2*dst32_linesize,     dst32_linesize, r2y, pattern, w, 2,3,0,1, 6,7,8,3,4,5,0,1,2); // 20 21 30 31 (horiz mirrored)
                  hq4x_interp_2x2(dst32 + 2*dst32_linesize + 2, dst32_linesize, r2y, pattern, w, 3,2,1,0, 8,7,6,5,4,3,2,1,0); // 22 23 32 33 (center mirrored)
              } else {
                  av_assert0(0);
              }
  
              src32 += 1;
              dst32 += n;
          }
  
          src += src_linesize;
          dst += dst_linesize * n;
      }
  }
  
  #define HQX_FUNC(size) \
  static int hq##size##x(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs) \
  { \
      hqx_filter(arg, jobnr, nb_jobs, size); \
      return 0; \
  }
  
  HQX_FUNC(2)
  HQX_FUNC(3)
  HQX_FUNC(4)
  
  static int query_formats(AVFilterContext *ctx)
  {
      static const enum AVPixelFormat pix_fmts[] = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};
      AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
      if (!fmts_list)
          return AVERROR(ENOMEM);
      return ff_set_common_formats(ctx, fmts_list);
  }
  
  static int config_output(AVFilterLink *outlink)
  {
      AVFilterContext *ctx = outlink->src;
      HQXContext *hqx = ctx->priv;
      AVFilterLink *inlink = ctx->inputs[0];
  
      outlink->w = inlink->w * hqx->n;
      outlink->h = inlink->h * hqx->n;
      av_log(inlink->dst, AV_LOG_VERBOSE, "fmt:%s size:%dx%d -> size:%dx%d\n",
             av_get_pix_fmt_name(inlink->format),
             inlink->w, inlink->h, outlink->w, outlink->h);
      return 0;
  }
  
  static int filter_frame(AVFilterLink *inlink, AVFrame *in)
  {
      AVFilterContext *ctx = inlink->dst;
      AVFilterLink *outlink = ctx->outputs[0];
      HQXContext *hqx = ctx->priv;
      ThreadData td;
      AVFrame *out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
      if (!out) {
          av_frame_free(&in);
          return AVERROR(ENOMEM);
      }
      av_frame_copy_props(out, in);
      out->width  = outlink->w;
      out->height = outlink->h;
  
      td.in = in;
      td.out = out;
      td.rgbtoyuv = hqx->rgbtoyuv;
      ctx->internal->execute(ctx, hqx->func, &td, NULL, FFMIN(inlink->h, ctx->graph->nb_threads));
  
      av_frame_free(&in);
      return ff_filter_frame(outlink, out);
  }
  
  static av_cold int init(AVFilterContext *ctx)
  {
      HQXContext *hqx = ctx->priv;
      static const hqxfunc_t hqxfuncs[] = {hq2x, hq3x, hq4x};
  
      uint32_t c;
      int bg, rg, g;
  
      for (bg=-255; bg<256; bg++) {
          for (rg=-255; rg<256; rg++) {
              const uint32_t u = (uint32_t)((-169*rg + 500*bg)/1000) + 128;
              const uint32_t v = (uint32_t)(( 500*rg -  81*bg)/1000) + 128;
              int startg = FFMAX3(-bg, -rg, 0);
              int endg = FFMIN3(255-bg, 255-rg, 255);
              uint32_t y = (uint32_t)(( 299*rg + 1000*startg + 114*bg)/1000);
              c = bg + (rg<<16) + 0x010101 * startg;
              for (g = startg; g <= endg; g++) {
                  hqx->rgbtoyuv[c] = ((y++) << 16) + (u << 8) + v;
                  c+= 0x010101;
              }
          }
      }
  
      hqx->func = hqxfuncs[hqx->n - 2];
      return 0;
  }
  
  static const AVFilterPad hqx_inputs[] = {
      {
          .name         = "default",
          .type         = AVMEDIA_TYPE_VIDEO,
          .filter_frame = filter_frame,
      },
      { NULL }
  };
  
  static const AVFilterPad hqx_outputs[] = {
      {
          .name         = "default",
          .type         = AVMEDIA_TYPE_VIDEO,
          .config_props = config_output,
      },
      { NULL }
  };
  
  AVFilter ff_vf_hqx = {
      .name          = "hqx",
      .description   = NULL_IF_CONFIG_SMALL("Scale the input by 2, 3 or 4 using the hq*x magnification algorithm."),
      .priv_size     = sizeof(HQXContext),
      .init          = init,
      .query_formats = query_formats,
      .inputs        = hqx_inputs,
      .outputs       = hqx_outputs,
      .priv_class    = &hqx_class,
      .flags         = AVFILTER_FLAG_SLICE_THREADS,
  };
  