pngtrans.c File Reference

#include "pngpriv.h"

Functions
void PNGAPI	png_set_bgr (png_structrp png_ptr)
void PNGAPI	png_set_swap (png_structrp png_ptr)
void PNGAPI	png_set_packing (png_structrp png_ptr)
void PNGAPI	png_set_packswap (png_structrp png_ptr)
void PNGAPI	png_set_shift (png_structrp png_ptr, png_const_color_8p true_bits)
int PNGAPI	png_set_interlace_handling (png_structrp png_ptr)
void PNGAPI	png_set_filler (png_structrp png_ptr, png_uint_32 filler, int filler_loc)
void PNGAPI	png_set_add_alpha (png_structrp png_ptr, png_uint_32 filler, int filler_loc)
void PNGAPI	png_set_swap_alpha (png_structrp png_ptr)
void PNGAPI	png_set_invert_alpha (png_structrp png_ptr)
void PNGAPI	png_set_invert_mono (png_structrp png_ptr)
void	png_do_invert (png_row_infop row_info, png_bytep row)
void	png_do_swap (png_row_infop row_info, png_bytep row)
void	png_do_packswap (png_row_infop row_info, png_bytep row)
void	png_do_strip_channel (png_row_infop row_info, png_bytep row, int at_start)
void	png_do_bgr (png_row_infop row_info, png_bytep row)
void	png_do_check_palette_indexes (png_structrp png_ptr, png_row_infop row_info)
void PNGAPI	png_set_user_transform_info (png_structrp png_ptr, png_voidp user_transform_ptr, int user_transform_depth, int user_transform_channels)
png_voidp PNGAPI	png_get_user_transform_ptr (png_const_structrp png_ptr)
png_uint_32 PNGAPI	png_get_current_row_number (png_const_structrp png_ptr)
png_byte PNGAPI	png_get_current_pass_number (png_const_structrp png_ptr)

Variables
static const png_byte	onebppswaptable [256]
static const png_byte	twobppswaptable [256]
static const png_byte	fourbppswaptable [256]

Function Documentation

png_set_bgr()

void PNGAPI png_set_bgr

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_bgr");
 
   if (png_ptr == NULL)
      return;
 
   png_ptr->transformations |= PNG_BGR;
}

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png_set_swap()

void PNGAPI png_set_swap

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_swap");
 
   if (png_ptr == NULL)
      return;
 
   if (png_ptr->bit_depth == 16)
      png_ptr->transformations |= PNG_SWAP_BYTES;
}

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png_set_packing()

void PNGAPI png_set_packing

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_packing");
 
   if (png_ptr == NULL)
      return;
 
   if (png_ptr->bit_depth < 8)
   {
      png_ptr->transformations |= PNG_PACK;
#     ifdef PNG_WRITE_SUPPORTED
         png_ptr->usr_bit_depth = 8;
#     endif
   }
}

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png_set_packswap()

void PNGAPI png_set_packswap

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_packswap");
 
   if (png_ptr == NULL)
      return;
 
   if (png_ptr->bit_depth < 8)
      png_ptr->transformations |= PNG_PACKSWAP;
}

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png_set_shift()

void PNGAPI png_set_shift	(	png_structrp	png_ptr,
		png_const_color_8p	true_bits
	)

{
   png_debug(1, "in png_set_shift");
 
   if (png_ptr == NULL)
      return;
 
   png_ptr->transformations |= PNG_SHIFT;
   png_ptr->shift = *true_bits;
}

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png_set_interlace_handling()

int PNGAPI png_set_interlace_handling

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_interlace handling");
 
   if (png_ptr != 0 && png_ptr->interlaced != 0)
   {
      png_ptr->transformations |= PNG_INTERLACE;
      return (7);
   }
 
   return (1);
}

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png_set_filler()

void PNGAPI png_set_filler	(	png_structrp	png_ptr,
		png_uint_32	filler,
		int	filler_loc
	)

{
   png_debug(1, "in png_set_filler");
 
   if (png_ptr == NULL)
      return;
 
   /* In libpng 1.6 it is possible to determine whether this is a read or write
    * operation and therefore to do more checking here for a valid call.
    */
   if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0)
   {
#     ifdef PNG_READ_FILLER_SUPPORTED
         /* On read png_set_filler is always valid, regardless of the base PNG
          * format, because other transformations can give a format where the
          * filler code can execute (basically an 8 or 16-bit component RGB or G
          * format.)
          *
          * NOTE: usr_channels is not used by the read code!  (This has led to
          * confusion in the past.)  The filler is only used in the read code.
          */
         png_ptr->filler = (png_uint_16)filler;
#     else
         png_app_error(png_ptr, "png_set_filler not supported on read");
         PNG_UNUSED(filler) /* not used in the write case */
         return;
#     endif
   }
 
   else /* write */
   {
#     ifdef PNG_WRITE_FILLER_SUPPORTED
         /* On write the usr_channels parameter must be set correctly at the
          * start to record the number of channels in the app-supplied data.
          */
         switch (png_ptr->color_type)
         {
            case PNG_COLOR_TYPE_RGB:
               png_ptr->usr_channels = 4;
               break;
 
            case PNG_COLOR_TYPE_GRAY:
               if (png_ptr->bit_depth >= 8)
               {
                  png_ptr->usr_channels = 2;
                  break;
               }
 
               else
               {
                  /* There simply isn't any code in libpng to strip out bits
                   * from bytes when the components are less than a byte in
                   * size!
                   */
                  png_app_error(png_ptr,
                      "png_set_filler is invalid for"
                      " low bit depth gray output");
                  return;
               }
 
            default:
               png_app_error(png_ptr,
                   "png_set_filler: inappropriate color type");
               return;
         }
#     else
         png_app_error(png_ptr, "png_set_filler not supported on write");
         return;
#     endif
   }
 
   /* Here on success - libpng supports the operation, set the transformation
    * and the flag to say where the filler channel is.
    */
   png_ptr->transformations |= PNG_FILLER;
 
   if (filler_loc == PNG_FILLER_AFTER)
      png_ptr->flags |= PNG_FLAG_FILLER_AFTER;
 
   else
      png_ptr->flags &= ~PNG_FLAG_FILLER_AFTER;
}

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png_set_add_alpha()

void PNGAPI png_set_add_alpha	(	png_structrp	png_ptr,
		png_uint_32	filler,
		int	filler_loc
	)

{
   png_debug(1, "in png_set_add_alpha");
 
   if (png_ptr == NULL)
      return;
 
   png_set_filler(png_ptr, filler, filler_loc);
   /* The above may fail to do anything. */
   if ((png_ptr->transformations & PNG_FILLER) != 0)
      png_ptr->transformations |= PNG_ADD_ALPHA;
}

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png_set_swap_alpha()

void PNGAPI png_set_swap_alpha

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_swap_alpha");
 
   if (png_ptr == NULL)
      return;
 
   png_ptr->transformations |= PNG_SWAP_ALPHA;
}

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png_set_invert_alpha()

void PNGAPI png_set_invert_alpha

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_invert_alpha");
 
   if (png_ptr == NULL)
      return;
 
   png_ptr->transformations |= PNG_INVERT_ALPHA;
}

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png_set_invert_mono()

void PNGAPI png_set_invert_mono

(

png_structrp

png_ptr

)

{
   png_debug(1, "in png_set_invert_mono");
 
   if (png_ptr == NULL)
      return;
 
   png_ptr->transformations |= PNG_INVERT_MONO;
}

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png_do_invert()

void png_do_invert	(	png_row_infop	row_info,
		png_bytep	row
	)

{
   png_debug(1, "in png_do_invert");
 
  /* This test removed from libpng version 1.0.13 and 1.2.0:
   *   if (row_info->bit_depth == 1 &&
   */
   if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
   {
      png_bytep rp = row;
      size_t i;
      size_t istop = row_info->rowbytes;
 
      for (i = 0; i < istop; i++)
      {
         *rp = (png_byte)(~(*rp));
         rp++;
      }
   }
 
   else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
      row_info->bit_depth == 8)
   {
      png_bytep rp = row;
      size_t i;
      size_t istop = row_info->rowbytes;
 
      for (i = 0; i < istop; i += 2)
      {
         *rp = (png_byte)(~(*rp));
         rp += 2;
      }
   }
 
#ifdef PNG_16BIT_SUPPORTED
   else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
      row_info->bit_depth == 16)
   {
      png_bytep rp = row;
      size_t i;
      size_t istop = row_info->rowbytes;
 
      for (i = 0; i < istop; i += 4)
      {
         *rp = (png_byte)(~(*rp));
         *(rp + 1) = (png_byte)(~(*(rp + 1)));
         rp += 4;
      }
   }
#endif
}

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png_do_swap()

void png_do_swap	(	png_row_infop	row_info,
		png_bytep	row
	)

{
   png_debug(1, "in png_do_swap");
 
   if (row_info->bit_depth == 16)
   {
      png_bytep rp = row;
      png_uint_32 i;
      png_uint_32 istop= row_info->width * row_info->channels;
 
      for (i = 0; i < istop; i++, rp += 2)
      {
#ifdef PNG_BUILTIN_BSWAP16_SUPPORTED
         /* Feature added to libpng-1.6.11 for testing purposes, not
          * enabled by default.
          */
         *(png_uint_16*)rp = __builtin_bswap16(*(png_uint_16*)rp);
#else
         png_byte t = *rp;
         *rp = *(rp + 1);
         *(rp + 1) = t;
#endif
      }
   }
}

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png_do_packswap()

void png_do_packswap	(	png_row_infop	row_info,
		png_bytep	row
	)

{
   png_debug(1, "in png_do_packswap");
 
   if (row_info->bit_depth < 8)
   {
      png_bytep rp;
      png_const_bytep end, table;
 
      end = row + row_info->rowbytes;
 
      if (row_info->bit_depth == 1)
         table = onebppswaptable;
 
      else if (row_info->bit_depth == 2)
         table = twobppswaptable;
 
      else if (row_info->bit_depth == 4)
         table = fourbppswaptable;
 
      else
         return;
 
      for (rp = row; rp < end; rp++)
         *rp = table[*rp];
   }
}

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png_do_strip_channel()

void png_do_strip_channel	(	png_row_infop	row_info,
		png_bytep	row,
		int	at_start
	)

{
   png_bytep sp = row; /* source pointer */
   png_bytep dp = row; /* destination pointer */
   png_bytep ep = row + row_info->rowbytes; /* One beyond end of row */
 
   /* At the start sp will point to the first byte to copy and dp to where
    * it is copied to.  ep always points just beyond the end of the row, so
    * the loop simply copies (channels-1) channels until sp reaches ep.
    *
    * at_start:        0 -- convert AG, XG, ARGB, XRGB, AAGG, XXGG, etc.
    *            nonzero -- convert GA, GX, RGBA, RGBX, GGAA, RRGGBBXX, etc.
    */
 
   /* GA, GX, XG cases */
   if (row_info->channels == 2)
   {
      if (row_info->bit_depth == 8)
      {
         if (at_start != 0) /* Skip initial filler */
            ++sp;
         else          /* Skip initial channel and, for sp, the filler */
         {
            sp += 2; ++dp;
         }
 
         /* For a 1 pixel wide image there is nothing to do */
         while (sp < ep)
         {
            *dp++ = *sp; sp += 2;
         }
 
         row_info->pixel_depth = 8;
      }
 
      else if (row_info->bit_depth == 16)
      {
         if (at_start != 0) /* Skip initial filler */
            sp += 2;
         else          /* Skip initial channel and, for sp, the filler */
         {
            sp += 4; dp += 2;
         }
 
         while (sp < ep)
         {
            *dp++ = *sp++; *dp++ = *sp; sp += 3;
         }
 
         row_info->pixel_depth = 16;
      }
 
      else
         return; /* bad bit depth */
 
      row_info->channels = 1;
 
      /* Finally fix the color type if it records an alpha channel */
      if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
         row_info->color_type = PNG_COLOR_TYPE_GRAY;
   }
 
   /* RGBA, RGBX, XRGB cases */
   else if (row_info->channels == 4)
   {
      if (row_info->bit_depth == 8)
      {
         if (at_start != 0) /* Skip initial filler */
            ++sp;
         else          /* Skip initial channels and, for sp, the filler */
         {
            sp += 4; dp += 3;
         }
 
         /* Note that the loop adds 3 to dp and 4 to sp each time. */
         while (sp < ep)
         {
            *dp++ = *sp++; *dp++ = *sp++; *dp++ = *sp; sp += 2;
         }
 
         row_info->pixel_depth = 24;
      }
 
      else if (row_info->bit_depth == 16)
      {
         if (at_start != 0) /* Skip initial filler */
            sp += 2;
         else          /* Skip initial channels and, for sp, the filler */
         {
            sp += 8; dp += 6;
         }
 
         while (sp < ep)
         {
            /* Copy 6 bytes, skip 2 */
            *dp++ = *sp++; *dp++ = *sp++;
            *dp++ = *sp++; *dp++ = *sp++;
            *dp++ = *sp++; *dp++ = *sp; sp += 3;
         }
 
         row_info->pixel_depth = 48;
      }
 
      else
         return; /* bad bit depth */
 
      row_info->channels = 3;
 
      /* Finally fix the color type if it records an alpha channel */
      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
         row_info->color_type = PNG_COLOR_TYPE_RGB;
   }
 
   else
      return; /* The filler channel has gone already */
 
   /* Fix the rowbytes value. */
   row_info->rowbytes = (size_t)(dp-row);
}

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png_do_bgr()

void png_do_bgr	(	png_row_infop	row_info,
		png_bytep	row
	)

{
   png_debug(1, "in png_do_bgr");
 
   if ((row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
   {
      png_uint_32 row_width = row_info->width;
      if (row_info->bit_depth == 8)
      {
         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
         {
            png_bytep rp;
            png_uint_32 i;
 
            for (i = 0, rp = row; i < row_width; i++, rp += 3)
            {
               png_byte save = *rp;
               *rp = *(rp + 2);
               *(rp + 2) = save;
            }
         }
 
         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
         {
            png_bytep rp;
            png_uint_32 i;
 
            for (i = 0, rp = row; i < row_width; i++, rp += 4)
            {
               png_byte save = *rp;
               *rp = *(rp + 2);
               *(rp + 2) = save;
            }
         }
      }
 
#ifdef PNG_16BIT_SUPPORTED
      else if (row_info->bit_depth == 16)
      {
         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
         {
            png_bytep rp;
            png_uint_32 i;
 
            for (i = 0, rp = row; i < row_width; i++, rp += 6)
            {
               png_byte save = *rp;
               *rp = *(rp + 4);
               *(rp + 4) = save;
               save = *(rp + 1);
               *(rp + 1) = *(rp + 5);
               *(rp + 5) = save;
            }
         }
 
         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
         {
            png_bytep rp;
            png_uint_32 i;
 
            for (i = 0, rp = row; i < row_width; i++, rp += 8)
            {
               png_byte save = *rp;
               *rp = *(rp + 4);
               *(rp + 4) = save;
               save = *(rp + 1);
               *(rp + 1) = *(rp + 5);
               *(rp + 5) = save;
            }
         }
      }
#endif
   }
}

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png_do_check_palette_indexes()

void png_do_check_palette_indexes	(	png_structrp	png_ptr,
		png_row_infop	row_info
	)

{
   if (png_ptr->num_palette < (1 << row_info->bit_depth) &&
      png_ptr->num_palette > 0) /* num_palette can be 0 in MNG files */
   {
      /* Calculations moved outside switch in an attempt to stop different
       * compiler warnings.  'padding' is in *bits* within the last byte, it is
       * an 'int' because pixel_depth becomes an 'int' in the expression below,
       * and this calculation is used because it avoids warnings that other
       * forms produced on either GCC or MSVC.
       */
      int padding = PNG_PADBITS(row_info->pixel_depth, row_info->width);
      png_bytep rp = png_ptr->row_buf + row_info->rowbytes - 1;
 
      switch (row_info->bit_depth)
      {
         case 1:
         {
            /* in this case, all bytes must be 0 so we don't need
             * to unpack the pixels except for the rightmost one.
             */
            for (; rp > png_ptr->row_buf; rp--)
            {
              if ((*rp >> padding) != 0)
                 png_ptr->num_palette_max = 1;
              padding = 0;
            }
 
            break;
         }
 
         case 2:
         {
            for (; rp > png_ptr->row_buf; rp--)
            {
              int i = ((*rp >> padding) & 0x03);
 
              if (i > png_ptr->num_palette_max)
                 png_ptr->num_palette_max = i;
 
              i = (((*rp >> padding) >> 2) & 0x03);
 
              if (i > png_ptr->num_palette_max)
                 png_ptr->num_palette_max = i;
 
              i = (((*rp >> padding) >> 4) & 0x03);
 
              if (i > png_ptr->num_palette_max)
                 png_ptr->num_palette_max = i;
 
              i = (((*rp >> padding) >> 6) & 0x03);
 
              if (i > png_ptr->num_palette_max)
                 png_ptr->num_palette_max = i;
 
              padding = 0;
            }
 
            break;
         }
 
         case 4:
         {
            for (; rp > png_ptr->row_buf; rp--)
            {
              int i = ((*rp >> padding) & 0x0f);
 
              if (i > png_ptr->num_palette_max)
                 png_ptr->num_palette_max = i;
 
              i = (((*rp >> padding) >> 4) & 0x0f);
 
              if (i > png_ptr->num_palette_max)
                 png_ptr->num_palette_max = i;
 
              padding = 0;
            }
 
            break;
         }
 
         case 8:
         {
            for (; rp > png_ptr->row_buf; rp--)
            {
               if (*rp > png_ptr->num_palette_max)
                  png_ptr->num_palette_max = (int) *rp;
            }
 
            break;
         }
 
         default:
            break;
      }
   }
}

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png_set_user_transform_info()

void PNGAPI png_set_user_transform_info	(	png_structrp	png_ptr,
		png_voidp	user_transform_ptr,
		int	user_transform_depth,
		int	user_transform_channels
	)

{
   png_debug(1, "in png_set_user_transform_info");
 
   if (png_ptr == NULL)
      return;
 
#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
   if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
      (png_ptr->flags & PNG_FLAG_ROW_INIT) != 0)
   {
      png_app_error(png_ptr,
          "info change after png_start_read_image or png_read_update_info");
      return;
   }
#endif
 
   png_ptr->user_transform_ptr = user_transform_ptr;
   png_ptr->user_transform_depth = (png_byte)user_transform_depth;
   png_ptr->user_transform_channels = (png_byte)user_transform_channels;
}

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png_get_user_transform_ptr()

png_voidp PNGAPI png_get_user_transform_ptr

(

png_const_structrp

png_ptr

)

{
   if (png_ptr == NULL)
      return (NULL);
 
   return png_ptr->user_transform_ptr;
}

png_get_current_row_number()

png_uint_32 PNGAPI png_get_current_row_number

(

png_const_structrp

png_ptr

)

{
   /* See the comments in png.h - this is the sub-image row when reading an
    * interlaced image.
    */
   if (png_ptr != NULL)
      return png_ptr->row_number;
 
   return PNG_UINT_32_MAX; /* help the app not to fail silently */
}

png_get_current_pass_number()

png_byte PNGAPI png_get_current_pass_number

(

png_const_structrp

png_ptr

)

{
   if (png_ptr != NULL)
      return png_ptr->pass;
   return 8; /* invalid */
}

Variable Documentation

onebppswaptable

const png_byte onebppswaptable[256]

static

twobppswaptable

const png_byte twobppswaptable[256]

static

fourbppswaptable

const png_byte fourbppswaptable[256]

static