Update bundled libpng to version 1.6.50 dated 2025-07-01

1 files changed, 78 insertions, 47 deletions

diff --git a/png/pngwrite.c b/png/pngwrite.c
index 77e412f43..35a5d17b6 100644
--- a/png/pngwrite.c
+++ b/png/pngwrite.c
@@ -1,7 +1,6 @@
-
 /* pngwrite.c - general routines to write a PNG file
  *
- * Copyright (c) 2018-2024 Cosmin Truta
+ * Copyright (c) 2018-2025 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.
@@ -128,61 +127,93 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
        * the application continues writing the PNG.  So check the 'invalid'
        * flag here too.
        */
-#ifdef PNG_GAMMA_SUPPORTED
-#  ifdef PNG_WRITE_gAMA_SUPPORTED
-      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-          (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_gAMA) != 0 &&
-          (info_ptr->valid & PNG_INFO_gAMA) != 0)
-         png_write_gAMA_fixed(png_ptr, info_ptr->colorspace.gamma);
-#  endif
+#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
+         /* Write unknown chunks first; PNG v3 establishes a precedence order
+          * for colourspace chunks.  It is certain therefore that new
+          * colourspace chunks will have a precedence and very likely it will be
+          * higher than all known so far.  Writing the unknown chunks here is
+          * most likely to present the chunks in the most convenient order.
+          *
+          * FUTURE: maybe write chunks in the order the app calls png_set_chnk
+          * to give the app control.
+          */
+         write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
 #endif
 
-#ifdef PNG_COLORSPACE_SUPPORTED
-      /* Write only one of sRGB or an ICC profile.  If a profile was supplied
-       * and it matches one of the known sRGB ones issue a warning.
-       */
-#  ifdef PNG_WRITE_iCCP_SUPPORTED
-         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-             (info_ptr->valid & PNG_INFO_iCCP) != 0)
-         {
-#    ifdef PNG_WRITE_sRGB_SUPPORTED
-               if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
-                  png_app_warning(png_ptr,
-                      "profile matches sRGB but writing iCCP instead");
-#     endif
+#ifdef PNG_WRITE_sBIT_SUPPORTED
+         /* PNG v3: a streaming app will need to see this before cICP because
+          * the information is helpful in handling HLG encoding (which is
+          * natively 10 bits but gets expanded to 16 in PNG.)
+          *
+          * The app shouldn't care about the order ideally, but it might have
+          * no choice.  In PNG v3, apps are allowed to reject PNGs where the
+          * APNG chunks are out of order so it behooves libpng to be nice here.
+          */
+         if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
+            png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
+#endif
 
+   /* PNG v3: the July 2004 version of the TR introduced the concept of colour
+    * space priority.  As above it therefore behooves libpng to write the colour
+    * space chunks in the priority order so that a streaming app need not buffer
+    * them.
+    *
+    * PNG v3: Chunks mDCV and cLLI provide ancillary information for the
+    * interpretation of the colourspace chunkgs but do not require support for
+    * those chunks so are outside the "COLORSPACE" check but before the write of
+    * the colourspace chunks themselves.
+    */
+#ifdef PNG_WRITE_cLLI_SUPPORTED
+   if ((info_ptr->valid & PNG_INFO_cLLI) != 0)
+   {
+      png_write_cLLI_fixed(png_ptr, info_ptr->maxCLL, info_ptr->maxFALL);
+   }
+#endif
+#ifdef PNG_WRITE_mDCV_SUPPORTED
+   if ((info_ptr->valid & PNG_INFO_mDCV) != 0)
+   {
+      png_write_mDCV_fixed(png_ptr,
+         info_ptr->mastering_red_x, info_ptr->mastering_red_y,
+         info_ptr->mastering_green_x, info_ptr->mastering_green_y,
+         info_ptr->mastering_blue_x, info_ptr->mastering_blue_y,
+         info_ptr->mastering_white_x, info_ptr->mastering_white_y,
+         info_ptr->mastering_maxDL, info_ptr->mastering_minDL);
+   }
+#endif
+
+#  ifdef PNG_WRITE_cICP_SUPPORTED /* Priority 4 */
+   if ((info_ptr->valid & PNG_INFO_cICP) != 0)
+      {
+         png_write_cICP(png_ptr,
+                        info_ptr->cicp_colour_primaries,
+                        info_ptr->cicp_transfer_function,
+                        info_ptr->cicp_matrix_coefficients,
+                        info_ptr->cicp_video_full_range_flag);
+      }
+#  endif
+
+#  ifdef PNG_WRITE_iCCP_SUPPORTED /* Priority 3 */
+         if ((info_ptr->valid & PNG_INFO_iCCP) != 0)
+         {
             png_write_iCCP(png_ptr, info_ptr->iccp_name,
-                info_ptr->iccp_profile);
+                info_ptr->iccp_profile, info_ptr->iccp_proflen);
          }
-#     ifdef PNG_WRITE_sRGB_SUPPORTED
-         else
-#     endif
 #  endif
 
-#  ifdef PNG_WRITE_sRGB_SUPPORTED
-         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-             (info_ptr->valid & PNG_INFO_sRGB) != 0)
-            png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
+#  ifdef PNG_WRITE_sRGB_SUPPORTED /* Priority 2 */
+         if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
+            png_write_sRGB(png_ptr, info_ptr->rendering_intent);
 #  endif /* WRITE_sRGB */
-#endif /* COLORSPACE */
 
-#ifdef PNG_WRITE_sBIT_SUPPORTED
-         if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
-            png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
-#endif
-
-#ifdef PNG_COLORSPACE_SUPPORTED
-#  ifdef PNG_WRITE_cHRM_SUPPORTED
-         if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
-             (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&
-             (info_ptr->valid & PNG_INFO_cHRM) != 0)
-            png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
+#  ifdef PNG_WRITE_gAMA_SUPPORTED /* Priority 1 */
+      if ((info_ptr->valid & PNG_INFO_gAMA) != 0)
+         png_write_gAMA_fixed(png_ptr, info_ptr->gamma);
 #  endif
-#endif
 
-#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-         write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
-#endif
+#  ifdef PNG_WRITE_cHRM_SUPPORTED /* Also priority 1 */
+         if ((info_ptr->valid & PNG_INFO_cHRM) != 0)
+            png_write_cHRM_fixed(png_ptr, &info_ptr->cHRM);
+#  endif
 
       png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;
    }
@@ -2302,7 +2333,7 @@ int PNGAPI
 png_image_write_to_stdio(png_imagep image, FILE *file, int convert_to_8bit,
     const void *buffer, png_int_32 row_stride, const void *colormap)
 {
-   /* Write the image to the given (FILE*). */
+   /* Write the image to the given FILE object. */
    if (image != NULL && image->version == PNG_IMAGE_VERSION)
    {
       if (file != NULL && buffer != NULL)