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Java example source code file (pngtrans.c)

This example Java source code file (pngtrans.c) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

null, png_16bit_supported, png_add_alpha, png_color_mask_color, png_color_type_gray_alpha, png_color_type_rgb, png_color_type_rgb_alpha, png_const, png_flag_filler_after, png_user_transform_info_supported, png_user_transform_ptr_supported, pngapi, private, skip

The pngtrans.c Java example source code

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/* pngtrans.c - transforms the data in a row (used by both readers and writers)
 *
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file and, per its terms, should not be removed:
 *
 * Last changed in libpng 1.5.4 [July 7, 2011]
 * Copyright (c) 1998-2011 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 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_structp png_ptr)
{
   png_debug(1, "in png_set_bgr");

   if (png_ptr == NULL)
      return;

   png_ptr->transformations |= PNG_BGR;
}
#endif

#if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
/* Turn on 16 bit byte swapping */
void PNGAPI
png_set_swap(png_structp 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;
}
#endif

#if defined(PNG_READ_PACK_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
/* Turn on pixel packing */
void PNGAPI
png_set_packing(png_structp 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;
      png_ptr->usr_bit_depth = 8;
   }
}
#endif

#if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
/* Turn on packed pixel swapping */
void PNGAPI
png_set_packswap(png_structp 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;
}
#endif

#if defined(PNG_READ_SHIFT_SUPPORTED) || defined(PNG_WRITE_SHIFT_SUPPORTED)
void PNGAPI
png_set_shift(png_structp 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;
}
#endif

#if defined(PNG_READ_INTERLACING_SUPPORTED) || \
    defined(PNG_WRITE_INTERLACING_SUPPORTED)
int PNGAPI
png_set_interlace_handling(png_structp png_ptr)
{
   png_debug(1, "in png_set_interlace handling");

   if (png_ptr && png_ptr->interlaced)
   {
      png_ptr->transformations |= PNG_INTERLACE;
      return (7);
   }

   return (1);
}
#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_structp png_ptr, png_uint_32 filler, int filler_loc)
{
   png_debug(1, "in png_set_filler");

   if (png_ptr == NULL)
      return;

   png_ptr->transformations |= PNG_FILLER;
   png_ptr->filler = (png_uint_16)filler;

   if (filler_loc == PNG_FILLER_AFTER)
      png_ptr->flags |= PNG_FLAG_FILLER_AFTER;

   else
      png_ptr->flags &= ~PNG_FLAG_FILLER_AFTER;

   /* This should probably go in the "do_read_filler" routine.
    * I attempted to do that in libpng-1.0.1a but that caused problems
    * so I restored it in libpng-1.0.2a
   */

   if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
   {
      png_ptr->usr_channels = 4;
   }

   /* Also I added this in libpng-1.0.2a (what happens when we expand
    * a less-than-8-bit grayscale to GA?) */

   if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY && png_ptr->bit_depth >= 8)
   {
      png_ptr->usr_channels = 2;
   }
}

/* Added to libpng-1.2.7 */
void PNGAPI
png_set_add_alpha(png_structp 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);
   png_ptr->transformations |= PNG_ADD_ALPHA;
}

#endif

#if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
    defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
void PNGAPI
png_set_swap_alpha(png_structp png_ptr)
{
   png_debug(1, "in png_set_swap_alpha");

   if (png_ptr == NULL)
      return;

   png_ptr->transformations |= PNG_SWAP_ALPHA;
}
#endif

#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
    defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
void PNGAPI
png_set_invert_alpha(png_structp 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_structp 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;
      png_size_t i;
      png_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;
      png_size_t i;
      png_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;
      png_size_t i;
      png_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)
{
   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)
      {
         png_byte t = *rp;
         *rp = *(rp + 1);
         *(rp + 1) = t;
      }
   }
}
#endif
#endif

#if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
static PNG_CONST png_byte onebppswaptable[256] = {
   0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
   0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
   0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
   0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
   0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4,
   0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
   0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
   0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
   0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2,
   0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
   0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
   0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
   0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6,
   0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
   0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE,
   0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
   0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1,
   0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
   0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9,
   0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
   0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
   0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
   0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED,
   0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
   0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3,
   0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
   0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB,
   0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
   0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7,
   0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
   0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF,
   0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
};

static PNG_CONST png_byte twobppswaptable[256] = {
   0x00, 0x40, 0x80, 0xC0, 0x10, 0x50, 0x90, 0xD0,
   0x20, 0x60, 0xA0, 0xE0, 0x30, 0x70, 0xB0, 0xF0,
   0x04, 0x44, 0x84, 0xC4, 0x14, 0x54, 0x94, 0xD4,
   0x24, 0x64, 0xA4, 0xE4, 0x34, 0x74, 0xB4, 0xF4,
   0x08, 0x48, 0x88, 0xC8, 0x18, 0x58, 0x98, 0xD8,
   0x28, 0x68, 0xA8, 0xE8, 0x38, 0x78, 0xB8, 0xF8,
   0x0C, 0x4C, 0x8C, 0xCC, 0x1C, 0x5C, 0x9C, 0xDC,
   0x2C, 0x6C, 0xAC, 0xEC, 0x3C, 0x7C, 0xBC, 0xFC,
   0x01, 0x41, 0x81, 0xC1, 0x11, 0x51, 0x91, 0xD1,
   0x21, 0x61, 0xA1, 0xE1, 0x31, 0x71, 0xB1, 0xF1,
   0x05, 0x45, 0x85, 0xC5, 0x15, 0x55, 0x95, 0xD5,
   0x25, 0x65, 0xA5, 0xE5, 0x35, 0x75, 0xB5, 0xF5,
   0x09, 0x49, 0x89, 0xC9, 0x19, 0x59, 0x99, 0xD9,
   0x29, 0x69, 0xA9, 0xE9, 0x39, 0x79, 0xB9, 0xF9,
   0x0D, 0x4D, 0x8D, 0xCD, 0x1D, 0x5D, 0x9D, 0xDD,
   0x2D, 0x6D, 0xAD, 0xED, 0x3D, 0x7D, 0xBD, 0xFD,
   0x02, 0x42, 0x82, 0xC2, 0x12, 0x52, 0x92, 0xD2,
   0x22, 0x62, 0xA2, 0xE2, 0x32, 0x72, 0xB2, 0xF2,
   0x06, 0x46, 0x86, 0xC6, 0x16, 0x56, 0x96, 0xD6,
   0x26, 0x66, 0xA6, 0xE6, 0x36, 0x76, 0xB6, 0xF6,
   0x0A, 0x4A, 0x8A, 0xCA, 0x1A, 0x5A, 0x9A, 0xDA,
   0x2A, 0x6A, 0xAA, 0xEA, 0x3A, 0x7A, 0xBA, 0xFA,
   0x0E, 0x4E, 0x8E, 0xCE, 0x1E, 0x5E, 0x9E, 0xDE,
   0x2E, 0x6E, 0xAE, 0xEE, 0x3E, 0x7E, 0xBE, 0xFE,
   0x03, 0x43, 0x83, 0xC3, 0x13, 0x53, 0x93, 0xD3,
   0x23, 0x63, 0xA3, 0xE3, 0x33, 0x73, 0xB3, 0xF3,
   0x07, 0x47, 0x87, 0xC7, 0x17, 0x57, 0x97, 0xD7,
   0x27, 0x67, 0xA7, 0xE7, 0x37, 0x77, 0xB7, 0xF7,
   0x0B, 0x4B, 0x8B, 0xCB, 0x1B, 0x5B, 0x9B, 0xDB,
   0x2B, 0x6B, 0xAB, 0xEB, 0x3B, 0x7B, 0xBB, 0xFB,
   0x0F, 0x4F, 0x8F, 0xCF, 0x1F, 0x5F, 0x9F, 0xDF,
   0x2F, 0x6F, 0xAF, 0xEF, 0x3F, 0x7F, 0xBF, 0xFF
};

static PNG_CONST png_byte fourbppswaptable[256] = {
   0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70,
   0x80, 0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0,
   0x01, 0x11, 0x21, 0x31, 0x41, 0x51, 0x61, 0x71,
   0x81, 0x91, 0xA1, 0xB1, 0xC1, 0xD1, 0xE1, 0xF1,
   0x02, 0x12, 0x22, 0x32, 0x42, 0x52, 0x62, 0x72,
   0x82, 0x92, 0xA2, 0xB2, 0xC2, 0xD2, 0xE2, 0xF2,
   0x03, 0x13, 0x23, 0x33, 0x43, 0x53, 0x63, 0x73,
   0x83, 0x93, 0xA3, 0xB3, 0xC3, 0xD3, 0xE3, 0xF3,
   0x04, 0x14, 0x24, 0x34, 0x44, 0x54, 0x64, 0x74,
   0x84, 0x94, 0xA4, 0xB4, 0xC4, 0xD4, 0xE4, 0xF4,
   0x05, 0x15, 0x25, 0x35, 0x45, 0x55, 0x65, 0x75,
   0x85, 0x95, 0xA5, 0xB5, 0xC5, 0xD5, 0xE5, 0xF5,
   0x06, 0x16, 0x26, 0x36, 0x46, 0x56, 0x66, 0x76,
   0x86, 0x96, 0xA6, 0xB6, 0xC6, 0xD6, 0xE6, 0xF6,
   0x07, 0x17, 0x27, 0x37, 0x47, 0x57, 0x67, 0x77,
   0x87, 0x97, 0xA7, 0xB7, 0xC7, 0xD7, 0xE7, 0xF7,
   0x08, 0x18, 0x28, 0x38, 0x48, 0x58, 0x68, 0x78,
   0x88, 0x98, 0xA8, 0xB8, 0xC8, 0xD8, 0xE8, 0xF8,
   0x09, 0x19, 0x29, 0x39, 0x49, 0x59, 0x69, 0x79,
   0x89, 0x99, 0xA9, 0xB9, 0xC9, 0xD9, 0xE9, 0xF9,
   0x0A, 0x1A, 0x2A, 0x3A, 0x4A, 0x5A, 0x6A, 0x7A,
   0x8A, 0x9A, 0xAA, 0xBA, 0xCA, 0xDA, 0xEA, 0xFA,
   0x0B, 0x1B, 0x2B, 0x3B, 0x4B, 0x5B, 0x6B, 0x7B,
   0x8B, 0x9B, 0xAB, 0xBB, 0xCB, 0xDB, 0xEB, 0xFB,
   0x0C, 0x1C, 0x2C, 0x3C, 0x4C, 0x5C, 0x6C, 0x7C,
   0x8C, 0x9C, 0xAC, 0xBC, 0xCC, 0xDC, 0xEC, 0xFC,
   0x0D, 0x1D, 0x2D, 0x3D, 0x4D, 0x5D, 0x6D, 0x7D,
   0x8D, 0x9D, 0xAD, 0xBD, 0xCD, 0xDD, 0xED, 0xFD,
   0x0E, 0x1E, 0x2E, 0x3E, 0x4E, 0x5E, 0x6E, 0x7E,
   0x8E, 0x9E, 0xAE, 0xBE, 0xCE, 0xDE, 0xEE, 0xFE,
   0x0F, 0x1F, 0x2F, 0x3F, 0x4F, 0x5F, 0x6F, 0x7F,
   0x8F, 0x9F, 0xAF, 0xBF, 0xCF, 0xDF, 0xEF, 0xFF
};

/* Swaps pixel packing order within bytes */
void /* PRIVATE */
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];
   }
}
#endif /* PNG_READ_PACKSWAP_SUPPORTED or PNG_WRITE_PACKSWAP_SUPPORTED */

#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)
{
   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) /* 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) /* 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) /* 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) /* 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 = dp-row;
}
#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)
{
   png_debug(1, "in png_do_bgr");

   if ((row_info->color_type & PNG_COLOR_MASK_COLOR))
   {
      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
   }
}
#endif /* PNG_READ_BGR_SUPPORTED or PNG_WRITE_BGR_SUPPORTED */

#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_structp 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;
   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;
}
#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_structp png_ptr)
{
   if (png_ptr == NULL)
      return (NULL);

   return ((png_voidp)png_ptr->user_transform_ptr);
}
#endif

#ifdef PNG_USER_TRANSFORM_INFO_SUPPORTED
png_uint_32 PNGAPI
png_get_current_row_number(png_const_structp png_ptr)
{
   /* See the comments in png.h - this is the sub-image row when reading and
    * interlaced image.
    */
   if (png_ptr != NULL)
      return png_ptr->row_number;

   return PNG_UINT_32_MAX; /* help the app not to fail silently */
}

png_byte PNGAPI
png_get_current_pass_number(png_const_structp png_ptr)
{
   if (png_ptr != NULL)
      return png_ptr->pass;
   return 8; /* invalid */
}
#endif /* PNG_USER_TRANSFORM_INFO_SUPPORTED */
#endif /* PNG_READ_USER_TRANSFORM_SUPPORTED ||
          PNG_WRITE_USER_TRANSFORM_SUPPORTED */
#endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */

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