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[wxWidgets.git] / src / png / pngwtran.c
diff --git a/src/png/pngwtran.c b/src/png/pngwtran.c
index 76cf3a3e5d9f638ee8ce253a5f579ebf50146036..96608efcb4a9f526e6fa8019254da4df24705022 100644 (file)
--- a/src/png/pngwtran.c
+++ b/src/png/pngwtran.c
@@ -1,92 +1,108 @@
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
- * libpng 1.0.3 - January 14, 1999
- * 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
- * Copyright (c) 1998, 1999 Glenn Randers-Pehrson
+ * Last changed in libpng 1.5.6 [November 3, 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
  */
 
  */
 
-#define PNG_INTERNAL
-#include "png.h"
+#include "pngpriv.h"
+
+#ifdef PNG_WRITE_SUPPORTED
 
 
+#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
 /* Transform the data according to the user's wishes.  The order of
  * transformations is significant.
  */
 /* Transform the data according to the user's wishes.  The order of
  * transformations is significant.
  */
-void
-png_do_write_transformations(png_structp png_ptr)
+void /* PRIVATE */
+png_do_write_transformations(png_structp png_ptr, png_row_infop row_info)
 {
 {
-   png_debug(1, "in png_do_write_transformations\n");
+   png_debug(1, "in png_do_write_transformations");
+
+   if (png_ptr == NULL)
+      return;
 
 
-#if defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
+#ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
-      if(png_ptr->write_user_transform_fn != NULL)
-        (*(png_ptr->write_user_transform_fn)) /* user write transform function */
-          (png_ptr,                    /* png_ptr */
-           &(png_ptr->row_info),       /* row_info:     */
-             /*  png_uint_32 width;          width of row */
-             /*  png_uint_32 rowbytes;       number of bytes in row */
-             /*  png_byte color_type;        color type of pixels */
-             /*  png_byte bit_depth;         bit depth of samples */
-             /*  png_byte channels;          number of channels (1-4) */
-             /*  png_byte pixel_depth;       bits per pixel (depth*channels) */
-           png_ptr->row_buf + 1);      /* start of pixel data for row */
+      if (png_ptr->write_user_transform_fn != NULL)
+         (*(png_ptr->write_user_transform_fn)) /* User write transform
+                                                 function */
+             (png_ptr,  /* png_ptr */
+             row_info,  /* row_info: */
+                /*  png_uint_32 width;       width of row */
+                /*  png_size_t rowbytes;     number of bytes in row */
+                /*  png_byte color_type;     color type of pixels */
+                /*  png_byte bit_depth;      bit depth of samples */
+                /*  png_byte channels;       number of channels (1-4) */
+                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
+             png_ptr->row_buf + 1);      /* start of pixel data for row */
 #endif
 #endif
-#if defined(PNG_WRITE_FILLER_SUPPORTED)
+
+#ifdef PNG_WRITE_FILLER_SUPPORTED
    if (png_ptr->transformations & PNG_FILLER)
    if (png_ptr->transformations & PNG_FILLER)
-      png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
-         png_ptr->flags);
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
+         !(png_ptr->flags & PNG_FLAG_FILLER_AFTER));
 #endif
 #endif
-#if defined(PNG_WRITE_PACKSWAP_SUPPORTED)
+
+#ifdef PNG_WRITE_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
    if (png_ptr->transformations & PNG_PACKSWAP)
-      png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_packswap(row_info, png_ptr->row_buf + 1);
 #endif
 #endif
-#if defined(PNG_WRITE_PACK_SUPPORTED)
+
+#ifdef PNG_WRITE_PACK_SUPPORTED
    if (png_ptr->transformations & PNG_PACK)
    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);
+      png_do_pack(row_info, png_ptr->row_buf + 1,
+          (png_uint_32)png_ptr->bit_depth);
 #endif
 #endif
-#if defined(PNG_WRITE_SWAP_SUPPORTED)
+
+#ifdef PNG_WRITE_SWAP_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_BYTES)
    if (png_ptr->transformations & PNG_SWAP_BYTES)
-      png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_swap(row_info, png_ptr->row_buf + 1);
 #endif
 #endif
-#if defined(PNG_WRITE_SHIFT_SUPPORTED)
+
+#ifdef PNG_WRITE_SHIFT_SUPPORTED
    if (png_ptr->transformations & PNG_SHIFT)
    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_INVERT_ALPHA_SUPPORTED)
-   if (png_ptr->transformations & PNG_INVERT_ALPHA)
-      png_do_write_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_shift(row_info, png_ptr->row_buf + 1,
+          &(png_ptr->shift));
 #endif
 #endif
-#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
+
+#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
-      png_do_write_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_write_swap_alpha(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
+   if (png_ptr->transformations & PNG_INVERT_ALPHA)
+      png_do_write_invert_alpha(row_info, png_ptr->row_buf + 1);
 #endif
 #endif
-#if defined(PNG_WRITE_BGR_SUPPORTED)
+
+#ifdef PNG_WRITE_BGR_SUPPORTED
    if (png_ptr->transformations & PNG_BGR)
    if (png_ptr->transformations & PNG_BGR)
-      png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_bgr(row_info, png_ptr->row_buf + 1);
 #endif
 #endif
-#if defined(PNG_WRITE_INVERT_SUPPORTED)
+
+#ifdef PNG_WRITE_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
    if (png_ptr->transformations & PNG_INVERT_MONO)
-      png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_invert(row_info, png_ptr->row_buf + 1);
 #endif
 }
 
 #endif
 }
 
-#if defined(PNG_WRITE_PACK_SUPPORTED)
+#ifdef 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).
  */
 /* 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
+void /* PRIVATE */
 png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
 {
 png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
 {
-   png_debug(1, "in png_do_pack\n");
+   png_debug(1, "in png_do_pack");
+
    if (row_info->bit_depth == 8 &&
    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)
       row_info->channels == 1)
    {
       switch ((int)bit_depth)
@@ -107,9 +123,12 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
             {
                if (*sp != 0)
                   v |= mask;
             {
                if (*sp != 0)
                   v |= mask;
+
                sp++;
                sp++;
+
                if (mask > 1)
                   mask >>= 1;
                if (mask > 1)
                   mask >>= 1;
+
                else
                {
                   mask = 0x80;
                else
                {
                   mask = 0x80;
@@ -118,10 +137,13 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
                   v = 0;
                }
             }
                   v = 0;
                }
             }
+
             if (mask != 0x80)
                *dp = (png_byte)v;
             if (mask != 0x80)
                *dp = (png_byte)v;
+
             break;
          }
             break;
          }
+
          case 2:
          {
             png_bytep sp, dp;
          case 2:
          {
             png_bytep sp, dp;
@@ -133,12 +155,14 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
             dp = row;
             shift = 6;
             v = 0;
             dp = row;
             shift = 6;
             v = 0;
+
             for (i = 0; i < row_width; i++)
             {
                png_byte value;
 
             for (i = 0; i < row_width; i++)
             {
                png_byte value;
 
-               value = (png_byte)(*sp & 0x3);
+               value = (png_byte)(*sp & 0x03);
                v |= (value << shift);
                v |= (value << shift);
+
                if (shift == 0)
                {
                   shift = 6;
                if (shift == 0)
                {
                   shift = 6;
@@ -146,14 +170,19 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
                   dp++;
                   v = 0;
                }
                   dp++;
                   v = 0;
                }
+
                else
                   shift -= 2;
                else
                   shift -= 2;
+
                sp++;
             }
                sp++;
             }
+
             if (shift != 6)
                *dp = (png_byte)v;
             if (shift != 6)
                *dp = (png_byte)v;
+
             break;
          }
             break;
          }
+
          case 4:
          {
             png_bytep sp, dp;
          case 4:
          {
             png_bytep sp, dp;
@@ -165,11 +194,12 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
             dp = row;
             shift = 4;
             v = 0;
             dp = row;
             shift = 4;
             v = 0;
+
             for (i = 0; i < row_width; i++)
             {
                png_byte value;
 
             for (i = 0; i < row_width; i++)
             {
                png_byte value;
 
-               value = (png_byte)(*sp & 0xf);
+               value = (png_byte)(*sp & 0x0f);
                v |= (value << shift);
 
                if (shift == 0)
                v |= (value << shift);
 
                if (shift == 0)
@@ -179,25 +209,32 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
                   dp++;
                   v = 0;
                }
                   dp++;
                   v = 0;
                }
+
                else
                   shift -= 4;
 
                sp++;
             }
                else
                   shift -= 4;
 
                sp++;
             }
+
             if (shift != 4)
                *dp = (png_byte)v;
             if (shift != 4)
                *dp = (png_byte)v;
+
             break;
          }
             break;
          }
+
+         default:
+            break;
       }
       }
+
       row_info->bit_depth = (png_byte)bit_depth;
       row_info->pixel_depth = (png_byte)(bit_depth * row_info->channels);
       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);
+      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
+          row_info->width);
    }
 }
 #endif
 
    }
 }
 #endif
 
-#if defined(PNG_WRITE_SHIFT_SUPPORTED)
+#ifdef 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
 /* 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
@@ -205,16 +242,13 @@ png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
  * would pass 3 as bit_depth, and this routine would translate the
  * data to 0 to 15.
  */
  * 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)
+void /* PRIVATE */
+png_do_shift(png_row_infop row_info, png_bytep row,
+    png_const_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)
+   png_debug(1, "in png_do_shift");
+
+   if (row_info->color_type != PNG_COLOR_TYPE_PALETTE)
    {
       int shift_start[4], shift_dec[4];
       int channels = 0;
    {
       int shift_start[4], shift_dec[4];
       int channels = 0;
@@ -224,19 +258,23 @@ png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
          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->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->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++;
       }
          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++;
       }
       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;
       if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
       {
          shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
@@ -244,18 +282,20 @@ png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
          channels++;
       }
 
          channels++;
       }
 
-      /* with low row depths, could only be grayscale, so one channel */
+      /* With low row depths, could only be grayscale, so one channel */
       if (row_info->bit_depth < 8)
       {
          png_bytep bp = row;
       if (row_info->bit_depth < 8)
       {
          png_bytep bp = row;
-         png_uint_32 i;
+         png_size_t i;
          png_byte mask;
          png_byte mask;
-         png_uint_32 row_bytes = row_info->rowbytes;
+         png_size_t row_bytes = row_info->rowbytes;
 
          if (bit_depth->gray == 1 && row_info->bit_depth == 2)
             mask = 0x55;
 
          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 if (row_info->bit_depth == 4 && bit_depth->gray == 3)
             mask = 0x11;
+
          else
             mask = 0xff;
 
          else
             mask = 0xff;
 
@@ -266,15 +306,18 @@ png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
 
             v = *bp;
             *bp = 0;
 
             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);
             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
                   *bp |= (png_byte)((v >> (-j)) & mask);
             }
          }
       }
+
       else if (row_info->bit_depth == 8)
       {
          png_bytep bp = row;
       else if (row_info->bit_depth == 8)
       {
          png_bytep bp = row;
@@ -290,15 +333,18 @@ png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
 
             v = *bp;
             *bp = 0;
 
             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);
             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
                   *bp |= (png_byte)((v >> (-j)) & 0xff);
             }
          }
       }
+
       else
       {
          png_bytep bp;
       else
       {
          png_bytep bp;
@@ -311,12 +357,14 @@ png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
             png_uint_16 value, v;
             int j;
 
             png_uint_16 value, v;
             int j;
 
-            v = ((png_uint_16)(*bp) << 8) + *(bp + 1);
+            v = (png_uint_16)(((png_uint_16)(*bp) << 8) + *(bp + 1));
             value = 0;
             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);
             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);
             }
                else
                   value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
             }
@@ -328,23 +376,22 @@ png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
 }
 #endif
 
 }
 #endif
 
-#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
-void
+#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
+void /* PRIVATE */
 png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
 {
 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
+   png_debug(1, "in png_do_write_swap_alpha");
+
    {
       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
       {
    {
       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
       {
-         /* This converts from ARGB to RGBA */
          if (row_info->bit_depth == 8)
          {
          if (row_info->bit_depth == 8)
          {
+            /* This converts from ARGB to RGBA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
+
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
                png_byte save = *(sp++);
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
                png_byte save = *(sp++);
@@ -354,9 +401,11 @@ png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
                *(dp++) = save;
             }
          }
                *(dp++) = save;
             }
          }
-         /* This converts from AARRGGBB to RRGGBBAA */
+
+#ifdef PNG_WRITE_16BIT_SUPPORTED
          else
          {
          else
          {
+            /* This converts from AARRGGBB to RRGGBBAA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
@@ -376,12 +425,14 @@ png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
                *(dp++) = save[1];
             }
          }
                *(dp++) = save[1];
             }
          }
+#endif /* PNG_WRITE_16BIT_SUPPORTED */
       }
       }
+
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
-         /* This converts from AG to GA */
          if (row_info->bit_depth == 8)
          {
          if (row_info->bit_depth == 8)
          {
+            /* This converts from AG to GA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
@@ -393,9 +444,11 @@ png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
                *(dp++) = save;
             }
          }
                *(dp++) = save;
             }
          }
-         /* This converts from AAGG to GGAA */
+
+#ifdef PNG_WRITE_16BIT_SUPPORTED
          else
          {
          else
          {
+            /* This converts from AAGG to GGAA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
@@ -411,61 +464,71 @@ png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
                *(dp++) = save[1];
             }
          }
                *(dp++) = save[1];
             }
          }
+#endif /* PNG_WRITE_16BIT_SUPPORTED */
       }
    }
 }
 #endif
 
       }
    }
 }
 #endif
 
-#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
-void
+#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
+void /* PRIVATE */
 png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
 {
 png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
 {
-   png_debug(1, "in png_do_write_invert_alpha\n");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
-   if (row != NULL && row_info != NULL)
-#endif
+   png_debug(1, "in png_do_write_invert_alpha");
+
    {
       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
       {
    {
       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
       {
-         /* This inverts the alpha channel in RGBA */
          if (row_info->bit_depth == 8)
          {
          if (row_info->bit_depth == 8)
          {
+            /* This inverts the alpha channel in RGBA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
+
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
+               /* Does nothing
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
-               *(dp++) = 255 - *(sp++);
+               */
+               sp+=3; dp = sp;
+               *(dp++) = (png_byte)(255 - *(sp++));
             }
          }
             }
          }
-         /* This inverts the alpha channel in RRGGBBAA */
+
+#ifdef PNG_WRITE_16BIT_SUPPORTED
          else
          {
          else
          {
+            /* This inverts the alpha channel in RRGGBBAA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
 
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
 
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
+               /* Does nothing
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
-               *(dp++) = 255 - *(sp++);
-               *(dp++) = 255 - *(sp++);
+               */
+               sp+=6; dp = sp;
+               *(dp++) = (png_byte)(255 - *(sp++));
+               *(dp++) = (png_byte)(255 - *(sp++));
             }
          }
             }
          }
+#endif /* PNG_WRITE_16BIT_SUPPORTED */
       }
       }
+
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
-         /* This inverts the alpha channel in GA */
          if (row_info->bit_depth == 8)
          {
          if (row_info->bit_depth == 8)
          {
+            /* This inverts the alpha channel in GA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
@@ -473,25 +536,98 @@ png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
                *(dp++) = *(sp++);
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
                *(dp++) = *(sp++);
-               *(dp++) = 255 - *(sp++);
+               *(dp++) = (png_byte)(255 - *(sp++));
             }
          }
             }
          }
-         /* This inverts the alpha channel in GGAA */
+
+#ifdef PNG_WRITE_16BIT_SUPPORTED
          else
          {
          else
          {
+            /* This inverts the alpha channel in GGAA */
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
 
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
             png_bytep sp, dp;
             png_uint_32 i;
             png_uint_32 row_width = row_info->width;
 
             for (i = 0, sp = dp = row; i < row_width; i++)
             {
+               /* Does nothing
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
                *(dp++) = *(sp++);
-               *(dp++) = 255 - *(sp++);
-               *(dp++) = 255 - *(sp++);
+               */
+               sp+=2; dp = sp;
+               *(dp++) = (png_byte)(255 - *(sp++));
+               *(dp++) = (png_byte)(255 - *(sp++));
             }
          }
             }
          }
+#endif /* PNG_WRITE_16BIT_SUPPORTED */
       }
    }
 }
 #endif
       }
    }
 }
 #endif
+#endif /* PNG_WRITE_TRANSFORMS_SUPPORTED */
+
+#ifdef PNG_MNG_FEATURES_SUPPORTED
+/* Undoes intrapixel differencing  */
+void /* PRIVATE */
+png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_write_intrapixel");
+
+   if ((row_info->color_type & PNG_COLOR_MASK_COLOR))
+   {
+      int bytes_per_pixel;
+      png_uint_32 row_width = row_info->width;
+      if (row_info->bit_depth == 8)
+      {
+         png_bytep rp;
+         png_uint_32 i;
+
+         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+            bytes_per_pixel = 3;
+
+         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+            bytes_per_pixel = 4;
+
+         else
+            return;
+
+         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+         {
+            *(rp)     = (png_byte)((*rp       - *(rp + 1)) & 0xff);
+            *(rp + 2) = (png_byte)((*(rp + 2) - *(rp + 1)) & 0xff);
+         }
+      }
+
+#ifdef PNG_WRITE_16BIT_SUPPORTED
+      else if (row_info->bit_depth == 16)
+      {
+         png_bytep rp;
+         png_uint_32 i;
+
+         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+            bytes_per_pixel = 6;
+
+         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+            bytes_per_pixel = 8;
+
+         else
+            return;
+
+         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+         {
+            png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);
+            png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);
+            png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);
+            png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);
+            png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
+            *(rp    ) = (png_byte)((red >> 8) & 0xff);
+            *(rp + 1) = (png_byte)(red & 0xff);
+            *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
+            *(rp + 5) = (png_byte)(blue & 0xff);
+         }
+      }
+#endif /* PNG_WRITE_16BIT_SUPPORTED */
+   }
+}
+#endif /* PNG_MNG_FEATURES_SUPPORTED */
+#endif /* PNG_WRITE_SUPPORTED */
wxWidgets (Impactor)