pngwtran.c

/* pngwtran.c - transforms the data in a row for PNG writers

   libpng 1.0 beta 6 - version 0.96
   For conditions of distribution and use, see copyright notice in png.h
   Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
   Copyright (c) 1996, 1997 Andreas Dilger
   May 12, 1997
   */

#define PNG_INTERNAL
#include "png.h"

/* transform the data according to the users wishes.  The order of
   transformations is significant. */
void
png_do_write_transformations(png_structp png_ptr)
{
   png_debug(1, "in png_do_write_transformations\n");
#if defined(PNG_WRITE_FILLER_SUPPORTED)
   if (png_ptr->transformations & PNG_FILLER)
      png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
         png_ptr->flags);
#endif
#if defined(PNG_WRITE_PACK_SUPPORTED)
   if (png_ptr->transformations & PNG_PACK)
      png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
         (png_uint_32)png_ptr->bit_depth);
#endif
#if defined(PNG_WRITE_SHIFT_SUPPORTED)
   if (png_ptr->transformations & PNG_SHIFT)
      png_do_shift(&(png_ptr->row_info), png_ptr->row_buf + 1,
         &(png_ptr->shift));
#endif
#if defined(PNG_WRITE_SWAP_SUPPORTED)
   if (png_ptr->transformations & PNG_SWAP_BYTES)
      png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
   if (png_ptr->transformations & PNG_SWAP_ALPHA)
      png_do_write_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
#if defined(PNG_WRITE_BGR_SUPPORTED)
   if (png_ptr->transformations & PNG_BGR)
      png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
#if defined(PNG_WRITE_INVERT_SUPPORTED)
   if (png_ptr->transformations & PNG_INVERT_MONO)
      png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
}

#if defined(PNG_WRITE_PACK_SUPPORTED)
/* pack pixels into bytes.  Pass the true bit depth in bit_depth.  The
   row_info bit depth should be 8 (one pixel per byte).  The channels
   should be 1 (this only happens on grayscale and paletted images) */
void
png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
{
   png_debug(1, "in png_do_pack\n");
   if (row_info->bit_depth == 8 &&
#if defined(PNG_USELESS_TESTS_SUPPORTED)
       row != NULL && row_info != NULL &&
#endif
      row_info->channels == 1)
   {
      switch ((int)bit_depth)
      {
         case 1:
         {
            png_bytep sp, dp;
            int mask, v;
            png_uint_32 i;

            sp = row;
            dp = row;
            mask = 0x80;
            v = 0;
            for (i = 0; i < row_info->width; i++)
            {
               if (*sp != 0)
                  v |= mask;
               sp++;
               if (mask > 1)
                  mask >>= 1;
               else
               {
                  mask = 0x80;
                  *dp = (png_byte)v;
                  dp++;
                  v = 0;
               }
            }
            if (mask != 0x80)
               *dp = (png_byte)v;
            break;
         }
         case 2:
         {
            png_bytep sp, dp;
            int shift, v;
            png_uint_32 i;

            sp = row;
            dp = row;
            shift = 6;
            v = 0;
            for (i = 0; i < row_info->width; i++)
            {
               png_byte value;

               value = (png_byte)(*sp & 0x3);
               v |= (value << shift);
               if (shift == 0)
               {
                  shift = 6;
                  *dp = (png_byte)v;
                  dp++;
                  v = 0;
               }
               else
                  shift -= 2;
               sp++;
            }
            if (shift != 6)
               *dp = (png_byte)v;
            break;
         }
         case 4:
         {
            png_bytep sp, dp;
            int shift, v;
            png_uint_32 i;

            sp = row;
            dp = row;
            shift = 4;
            v = 0;
            for (i = 0; i < row_info->width; i++)
            {
               png_byte value;

               value = (png_byte)(*sp & 0xf);
               v |= (value << shift);

               if (shift == 0)
               {
                  shift = 4;
                  *dp = (png_byte)v;
                  dp++;
                  v = 0;
               }
               else
                  shift -= 4;

               sp++;
            }
            if (shift != 4)
               *dp = (png_byte)v;
            break;
         }
      }
      row_info->bit_depth = (png_byte)bit_depth;
      row_info->pixel_depth = (png_byte)(bit_depth * row_info->channels);
      row_info->rowbytes =
         ((row_info->width * row_info->pixel_depth + 7) >> 3);
   }
}
#endif

#if defined(PNG_WRITE_SHIFT_SUPPORTED)
/* shift pixel values to take advantage of whole range.  Pass the
   true number of bits in bit_depth.  The row should be packed
   according to row_info->bit_depth.  Thus, if you had a row of
   bit depth 4, but the pixels only had values from 0 to 7, you
   would pass 3 as bit_depth, and this routine would translate the
   data to 0 to 15. */
void
png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
{
   png_debug(1, "in png_do_shift\n");
#if defined(PNG_USELESS_TESTS_SUPPORTED)
   if (row != NULL && row_info != NULL &&
#else
   if (
#endif
      row_info->color_type != PNG_COLOR_TYPE_PALETTE)
   {
      int shift_start[4], shift_dec[4];
      png_uint_32 channels;

      channels = 0;
      if (row_info->color_type & PNG_COLOR_MASK_COLOR)
      {
         shift_start[channels] = row_info->bit_depth - bit_depth->red;
         shift_dec[channels] = bit_depth->red;
         channels++;
         shift_start[channels] = row_info->bit_depth - bit_depth->green;
         shift_dec[channels] = bit_depth->green;
         channels++;
         shift_start[channels] = row_info->bit_depth - bit_depth->blue;
         shift_dec[channels] = bit_depth->blue;
         channels++;
      }
      else
      {
         shift_start[channels] = row_info->bit_depth - bit_depth->gray;
         shift_dec[channels] = bit_depth->gray;
         channels++;
      }
      if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
      {
         shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
         shift_dec[channels] = bit_depth->alpha;
         channels++;
      }

      /* with low row dephts, could only be grayscale, so one channel */
      if (row_info->bit_depth < 8)
      {
         png_bytep bp;
         png_uint_32 i;
         png_byte mask;

         if (bit_depth->gray == 1 && row_info->bit_depth == 2)
            mask = 0x55;
         else if (row_info->bit_depth == 4 && bit_depth->gray == 3)
            mask = 0x11;
         else
            mask = 0xff;

         for (bp = row, i = 0; i < row_info->rowbytes; i++, bp++)
         {
            png_uint_16 v;
            int j;

            v = *bp;
            *bp = 0;
            for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
            {
               if (j > 0)
                  *bp |= (png_byte)((v << j) & 0xff);
               else
                  *bp |= (png_byte)((v >> (-j)) & mask);
            }
         }
      }
      else if (row_info->bit_depth == 8)
      {
         png_bytep bp;
         png_uint_32 i;

         for (bp = row, i = 0; i < row_info->width; i++)
         {
            int c;

            for (c = 0; c < channels; c++, bp++)
            {
               png_uint_16 v;
               int j;

               v = *bp;
               *bp = 0;
               for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
               {
                  if (j > 0)
                     *bp |= (png_byte)((v << j) & 0xff);
                  else
                     *bp |= (png_byte)((v >> (-j)) & 0xff);
               }
            }
         }
      }
      else
      {
         png_bytep bp;
         png_uint_32 i;

         for (bp = row, i = 0; i < row_info->width * row_info->channels; i++)
         {
            int c;

            for (c = 0; c < channels; c++, bp += 2)
            {
               png_uint_16 value, v;
               int j;

               v = ((png_uint_16)(*bp) << 8) + *(bp + 1);
               value = 0;
               for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
               {
                  if (j > 0)
                     value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
                  else
                     value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
               }
               *bp = (png_byte)(value >> 8);
               *(bp + 1) = (png_byte)(value & 0xff);
            }
         }
      }
   }
}
#endif

#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
void
png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
{
   png_debug(1, "in png_do_write_swap_alpha\n");
#if defined(PNG_USELESS_TESTS_SUPPORTED)
   if (row != NULL && row_info != NULL)
#endif
   {
      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
      {
         /* This converts from ARGB to RGBA */
         if (row_info->bit_depth == 8)
         {
            png_bytep sp, dp;
            png_byte save;
            png_uint_32 i;

            for (i = 0, sp = dp = row; i < row_info->width; i++)
            {
               save = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = save;
            }
         }
         /* This converts from AARRGGBB to RRGGBBAA */
         else
         {
            png_bytep sp, dp;
            png_byte save[2];
            png_uint_32 i;

            for (i = 0, sp = dp = row; i < row_info->width; i++)
            {
               save[0] = *(sp++);
               save[1] = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = save[0];
               *(dp++) = save[1];
            }
         }
      }
      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
      {
         /* This converts from AG to GA */
         if (row_info->bit_depth == 8)
         {
            png_bytep sp, dp;
            png_byte save;
            png_uint_32 i;

            for (i = 0, sp = dp = row; i < row_info->width; i++)
            {
               save = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = save;
            }
         }
         /* This converts from AAGG to GGAA */
         else
         {
            png_bytep sp, dp;
            png_byte save[2];
            png_uint_32 i;

            for (i = 0, sp = dp = row; i < row_info->width; i++)
            {
               save[0] = *(sp++);
               save[1] = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = *(sp++);
               *(dp++) = save[0];
               *(dp++) = save[1];
            }
         }
      }
   }
}
#endif