[gimp] file-png: Call png_set_*() functions after png_set_IHDR()

[Mukund Sivaraman <muks src gnome org>]

commit fbbeb8d629eb78728396025432bb8be2078461fe
Author: Mukund Sivaraman <muks banu com>
Date:   Thu May 5 20:36:45 2011 +0530

    file-png: Call png_set_*() functions after png_set_IHDR()

 plug-ins/common/file-png.c |   80 +++++++++++++++++++++++++++++++------------
 1 files changed, 57 insertions(+), 23 deletions(-)
---
diff --git a/plug-ins/common/file-png.c b/plug-ins/common/file-png.c
index e34f0af..f798999 100644
--- a/plug-ins/common/file-png.c
+++ b/plug-ins/common/file-png.c
@@ -106,6 +106,17 @@ typedef struct
 }
 PngSaveGui;
 
+/* These are not saved or restored. */
+typedef struct
+{
+  gboolean   has_trns;
+  png_bytep  trans;
+  int        num_trans;
+  gboolean   has_plte;
+  png_colorp palette;
+  int        num_palette;
+}
+PngGlobals;
 
 /*
  * Local functions...
@@ -175,6 +186,7 @@ static const PngSaveVals defaults =
 };
 
 static PngSaveVals pngvals;
+static PngGlobals pngg;
 
 
 /*
@@ -1217,7 +1229,6 @@ save_image (const gchar  *filename,
   GimpPixelRgn pixel_rgn;       /* Pixel region for layer */
   png_structp pp;               /* PNG read pointer */
   png_infop info;               /* PNG info pointer */
-  gint num_colors;              /* Number of colors in colormap */
   gint offx, offy;              /* Drawable offsets from origin */
   guchar **pixels,              /* Pixel rows */
    *fixed,                      /* Fixed-up pixel data */
@@ -1230,7 +1241,6 @@ save_image (const gchar  *filename,
   struct tm *gmt;               /* GMT broken down */
   int color_type;
   int bit_depth;
-  png_colorp palette;
 
   guchar remap[256];            /* Re-mapping for the palette */
 
@@ -1309,9 +1319,9 @@ save_image (const gchar  *filename,
     case GIMP_INDEXED_IMAGE:
       bpp = 1;
       color_type = PNG_COLOR_TYPE_PALETTE;
-      palette = (png_colorp) gimp_image_get_colormap (image_ID, &num_colors);
-      png_set_PLTE (pp, info, palette, num_colors);
-      bit_depth = get_bit_depth_for_palette (num_colors);
+      pngg.has_plte = TRUE;
+      pngg.palette = (png_colorp) gimp_image_get_colormap (image_ID, &pngg.num_palette);
+      bit_depth = get_bit_depth_for_palette (pngg.num_palette);
       break;
 
     case GIMP_INDEXEDA_IMAGE:
@@ -1326,6 +1336,29 @@ save_image (const gchar  *filename,
       return FALSE;
     }
 
+  /* Set the image dimensions, bit depth, interlacing and compression */
+
+  png_set_IHDR (pp, info, drawable->width, drawable->height,
+                bit_depth,
+                color_type,
+                pngvals.interlaced ? PNG_INTERLACE_ADAM7 : PNG_INTERLACE_NONE,
+                PNG_COMPRESSION_TYPE_BASE,
+                PNG_FILTER_TYPE_BASE);
+
+  if (pngg.has_trns)
+    {
+      png_set_tRNS (pp, info, pngg.trans, pngg.num_trans, NULL);
+    }
+
+  if (pngg.has_plte)
+    {
+      png_set_PLTE (pp, info, pngg.palette, pngg.num_palette);
+    }
+
+  /* Set the compression level */
+
+  png_set_compression_level (pp, pngvals.compression_level);
+
   /* All this stuff is optional extras, if the user is aiming for smallest
      possible file size she can turn them all off */
 
@@ -1420,18 +1453,6 @@ save_image (const gchar  *filename,
   }
 #endif
 
-  /*
-   * Set the image dimensions, bit depth, interlacing and compression
-   */
-
-  png_set_IHDR (pp, info, drawable->width, drawable->height,
-                bit_depth,
-                color_type,
-                pngvals.interlaced ? PNG_INTERLACE_ADAM7 : PNG_INTERLACE_NONE,
-                PNG_COMPRESSION_TYPE_BASE,
-                PNG_FILTER_TYPE_BASE);
-  png_set_compression_level (pp, pngvals.compression_level);
-
   if (pngvals.comment)
     {
       GimpParasite *parasite;
@@ -1721,7 +1742,7 @@ respin_cmap (png_structp   pp,
              gint32        image_ID,
              GimpDrawable *drawable)
 {
-  static const guchar trans[] = { 0 };
+  static guchar trans[] = { 0 };
 
   gint          colors;
   guchar       *before;
@@ -1748,10 +1769,13 @@ respin_cmap (png_structp   pp,
                                      * index - do like gif2png and swap
                                      * index 0 and index transparent */
         {
-          png_color palette[256];
+          static png_color palette[256];
           gint      i;
 
-          png_set_tRNS (pp, info, (png_bytep) trans, 1, NULL);
+          /* Set tRNS chunk values for writing later. */
+          pngg.has_trns = TRUE;
+          pngg.trans = trans;
+          pngg.num_trans = 1;
 
           /* Transform all pixels with a value = transparent to
            * 0 and vice versa to compensate for re-ordering in palette
@@ -1772,7 +1796,10 @@ respin_cmap (png_structp   pp,
               palette[i].blue = before[3 * remap[i] + 2];
             }
 
-          png_set_PLTE (pp, info, palette, colors);
+          /* Set PLTE chunk values for writing later. */
+          pngg.has_plte = TRUE;
+          pngg.palette = palette;
+          pngg.num_palette = colors;
         }
       else
         {
@@ -1780,12 +1807,19 @@ respin_cmap (png_structp   pp,
            * transparency & just use the full palette */
           g_message (_("Couldn't losslessly save transparency, "
                        "saving opacity instead."));
-          png_set_PLTE (pp, info, (png_colorp) before, colors);
+
+          /* Set PLTE chunk values for writing later. */
+          pngg.has_plte = TRUE;
+          pngg.palette = (png_colorp) before;
+          pngg.num_palette = colors;
         }
     }
   else
     {
-      png_set_PLTE (pp, info, (png_colorp) before, colors);
+      /* Set PLTE chunk values for writing later. */
+      pngg.has_plte = TRUE;
+      pngg.palette = (png_colorp) before;
+      pngg.num_palette = colors;
     }
 
   return get_bit_depth_for_palette (colors);