pngminus: Expect all image transformations to be available in libpng

The pngminus programs use several PNG image transformations:
`png_set_expand`, `png_set_expand_1_2_4_to_8`, etc. (in png2pnm.c);
`png_set_packing`, `png_set_invert_mono`, etc. (in pnm2png.c).
The availability of all of these transformations in libpng is now
required at compile time.

On the topic of transformations, apply an unrelated fix to the use
of `png_set_gamma`.

2 files changed, 7 insertions, 18 deletions

diff --git a/contrib/pngminus/png2pnm.c b/contrib/pngminus/png2pnm.c
index de58dfdc3..bb159e213 100644
--- a/contrib/pngminus/png2pnm.c
+++ b/contrib/pngminus/png2pnm.c
@@ -224,7 +224,7 @@ BOOL png2pnm_internal (png_struct *png_ptr, png_info *info_ptr,
   /* set up (if applicable) the expansion of grayscale images to bit-depth 8 */
   png_set_expand_gray_1_2_4_to_8 (png_ptr);
 
-#ifdef NJET /* FIXME */
+#ifdef NJET
   /* downgrade 16-bit images to 8-bit */
   if (bit_depth == 16)
     png_set_strip_16 (png_ptr);
@@ -232,9 +232,12 @@ BOOL png2pnm_internal (png_struct *png_ptr, png_info *info_ptr,
   if (color_type == PNG_COLOR_TYPE_GRAY ||
       color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
     png_set_gray_to_rgb (png_ptr);
-  /* only if file has a file gamma, we do a correction */
-  if (png_get_gAMA (png_ptr, info_ptr, &file_gamma))
-    png_set_gamma (png_ptr, (double) 2.2, file_gamma);
+  /* if the PNG image has a gAMA chunk then gamma-correct the output image */
+  {
+    double file_gamma;
+    if (png_get_gAMA (png_ptr, info_ptr, &file_gamma))
+      png_set_gamma (png_ptr, (double) 2.2, file_gamma);
+  }
 #endif
 
   /* read the image file, with all of the above image transforms applied */
diff --git a/contrib/pngminus/pnm2png.c b/contrib/pngminus/pnm2png.c
index 5558023be..b89b73266 100644
--- a/contrib/pngminus/pnm2png.c
+++ b/contrib/pngminus/pnm2png.c
@@ -222,9 +222,7 @@ BOOL pnm2png_internal (png_struct *png_ptr, png_info *info_ptr,
   png_uint_32   alpha_width = 0, alpha_height = 0;
   int           alpha_depth = 0, alpha_present = 0;
   BOOL          alpha_raw = FALSE;
-#if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
   BOOL          packed_bitmap = FALSE;
-#endif
 
   /* read header of PNM file */
 
@@ -247,16 +245,10 @@ BOOL pnm2png_internal (png_struct *png_ptr, png_info *info_ptr,
 
   if ((magic_token[1] == '1') || (magic_token[1] == '4'))
   {
-#if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
     raw = (magic_token[1] == '4');
     bit_depth = 1;
     color_type = PNG_COLOR_TYPE_GRAY;
     packed_bitmap = TRUE;
-#else
-    fprintf (stderr, "PNM2PNG built without PNG_WRITE_INVERT_SUPPORTED and\n");
-    fprintf (stderr, "PNG_WRITE_PACK_SUPPORTED can't read PBM (P1,P4) files\n");
-    return FALSE;
-#endif
   }
   else if ((magic_token[1] == '2') || (magic_token[1] == '5'))
   {
@@ -356,14 +348,12 @@ BOOL pnm2png_internal (png_struct *png_ptr, png_info *info_ptr,
 
   alpha_present = (channels - 1) % 2;
 
-#if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
   if (packed_bitmap)
   {
     /* row data is as many bytes as can fit width x channels x bit_depth */
     row_bytes = (width * channels * bit_depth + 7) / 8;
   }
   else
-#endif
   {
     /* row_bytes is the width x number of channels x (bit-depth / 8) */
     row_bytes = width * channels * ((bit_depth <= 8) ? 1 : 2);
@@ -396,7 +386,6 @@ BOOL pnm2png_internal (png_struct *png_ptr, png_info *info_ptr,
   for (row = 0; row < height; row++)
   {
     pix_ptr = row_pointers[row];
-#if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
     if (packed_bitmap)
     {
       for (i = 0; i < row_bytes; i++)
@@ -406,7 +395,6 @@ BOOL pnm2png_internal (png_struct *png_ptr, png_info *info_ptr,
       }
     }
     else
-#endif
     {
       for (col = 0; col < width; col++)
       {
@@ -466,13 +454,11 @@ BOOL pnm2png_internal (png_struct *png_ptr, png_info *info_ptr,
                 (!interlace) ? PNG_INTERLACE_NONE : PNG_INTERLACE_ADAM7,
                 PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 
-#if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
   if (packed_bitmap == TRUE)
   {
     png_set_packing (png_ptr);
     png_set_invert_mono (png_ptr);
   }
-#endif
 
   /* write the file header information */
   png_write_info (png_ptr, info_ptr);