pngtrans.c | Explore in Territory


/* pngtrans.c - transforms the data in a row (used by both readers and writers)
 *
 * Copyright (c) 2018-2024 Cosmin Truta
 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
 * Copyright (c) 1996-1997 Andreas Dilger
 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 */

#include "pngpriv.h"

#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

#if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
/* Turn on BGR-to-RGB mapping */
void PNGAPI
png_set_bgr(png_structrp png_ptr)
{ … }
#endif

#if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
/* Turn on 16-bit byte swapping */
void PNGAPI
png_set_swap(png_structrp png_ptr)
{ … }
#endif

#if defined(PNG_READ_PACK_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
/* Turn on pixel packing */
void PNGAPI
png_set_packing(png_structrp png_ptr)
{ … }
#endif

#if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
/* Turn on packed pixel swapping */
void PNGAPI
png_set_packswap(png_structrp png_ptr)
{ … }
#endif

#if defined(PNG_READ_SHIFT_SUPPORTED) || defined(PNG_WRITE_SHIFT_SUPPORTED)
void PNGAPI
png_set_shift(png_structrp png_ptr, png_const_color_8p true_bits)
{ … }
#endif

#if defined(PNG_READ_INTERLACING_SUPPORTED) || \
    defined(PNG_WRITE_INTERLACING_SUPPORTED)
int PNGAPI
png_set_interlace_handling(png_structrp png_ptr)
{ … }
#endif

#if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
/* Add a filler byte on read, or remove a filler or alpha byte on write.
 * The filler type has changed in v0.95 to allow future 2-byte fillers
 * for 48-bit input data, as well as to avoid problems with some compilers
 * that don't like bytes as parameters.
 */
void PNGAPI
png_set_filler(png_structrp png_ptr, png_uint_32 filler, int filler_loc)
{ … }

/* Added to libpng-1.2.7 */
void PNGAPI
png_set_add_alpha(png_structrp png_ptr, png_uint_32 filler, int filler_loc)
{ … }

#endif

#if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
    defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
void PNGAPI
png_set_swap_alpha(png_structrp png_ptr)
{ … }
#endif

#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
    defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
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;
}
#endif

#if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
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;
}

/* Invert monochrome grayscale data */
void /* PRIVATE */
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
}
#endif

#ifdef PNG_16BIT_SUPPORTED
#if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
/* Swaps byte order on 16-bit depth images */
void /* PRIVATE */
png_do_swap(png_row_infop row_info, png_bytep row)
{ … }
#endif
#endif

#if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
static const png_byte onebppswaptable[256] = …;

static const png_byte twobppswaptable[256] = …;

static const png_byte fourbppswaptable[256] = …;

/* Swaps pixel packing order within bytes */
void /* PRIVATE */
png_do_packswap(png_row_infop row_info, png_bytep row)
{ … }
#endif /* PACKSWAP || WRITE_PACKSWAP */

#if defined(PNG_WRITE_FILLER_SUPPORTED) || \
    defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
/* Remove a channel - this used to be 'png_do_strip_filler' but it used a
 * somewhat weird combination of flags to determine what to do.  All the calls
 * to png_do_strip_filler are changed in 1.5.2 to call this instead with the
 * correct arguments.
 *
 * The routine isn't general - the channel must be the channel at the start or
 * end (not in the middle) of each pixel.
 */
void /* PRIVATE */
png_do_strip_channel(png_row_infop row_info, png_bytep row, int at_start)
{ … }
#endif

#if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
/* Swaps red and blue bytes within a pixel */
void /* PRIVATE */
png_do_bgr(png_row_infop row_info, png_bytep row)
{ … }
#endif /* READ_BGR || WRITE_BGR */

#if defined(PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED) || \
    defined(PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED)
/* Added at libpng-1.5.10 */
void /* PRIVATE */
png_do_check_palette_indexes(png_structrp png_ptr, png_row_infop row_info)
{
   png_debug(1, "in png_do_check_palette_indexes");

   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;

      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;
      }
   }
}
#endif /* CHECK_FOR_INVALID_INDEX */

#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
void PNGAPI
png_set_user_transform_info(png_structrp png_ptr, png_voidp
   user_transform_ptr, int user_transform_depth, int user_transform_channels)
{ … }
#endif

/* This function returns a pointer to the user_transform_ptr associated with
 * the user transform functions.  The application should free any memory
 * associated with this pointer before png_write_destroy and png_read_destroy
 * are called.
 */
#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
png_voidp PNGAPI
png_get_user_transform_ptr(png_const_structrp png_ptr)
{ … }
#endif

#ifdef PNG_USER_TRANSFORM_INFO_SUPPORTED
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)
{ … }
#endif /* USER_TRANSFORM_INFO */
#endif /* READ_USER_TRANSFORM || WRITE_USER_TRANSFORM */
#endif /* READ || WRITE */
chromium/third_party/libpng/pngtrans.c
