[libpng16] Changed ICC profile support to allow use of an external color

management system (CMS). In practice it is not possible to obtain cHRM
information reliably using just the end-point tags because they do not exist
in the vast majority of profiles.  Instead it is necessary to run the endpoints
through the ICC colorimetric intent transform (as described in the v4
spec).  Since this is likely to be too much code inside libpng for too
little gain (it implies a fairly complete CMS implementation) the code
has been changed to allow an external CMS to be used.  This code is
temporarily disabled until a suitable set of test cases using one or more
external CMS implementations have been implemented.

1 files changed, 32 insertions, 8 deletions

diff --git a/pngpriv.h b/pngpriv.h
index b01c00d10..6c46e47e0 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1406,9 +1406,12 @@ PNG_INTERNAL_FUNCTION(void,png_do_write_intrapixel,(png_row_infop row_info,
 
 /* Added at libpng version 1.6.0 */
 #ifdef PNG_GAMMA_SUPPORTED
-PNG_INTERNAL_FUNCTION(int,png_colorspace_set_gamma,(png_const_structrp png_ptr,
-    png_colorspacerp colorspace, png_fixed_point gAMA, int preferred),
-    PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_colorspace_set_gamma,(png_const_structrp png_ptr,
+    png_colorspacerp colorspace, png_fixed_point gAMA), PNG_EMPTY);
+   /* Set the colorspace gamma with a value provided by the application or by
+    * the gAMA chunk on read.  The value will override anything set by an ICC
+    * profile.
+    */
 
 PNG_INTERNAL_FUNCTION(void,png_colorspace_sync_info,(png_const_structrp png_ptr,
     png_inforp info_ptr), PNG_EMPTY);
@@ -1436,7 +1439,12 @@ PNG_INTERNAL_FUNCTION(int,png_colorspace_set_endpoints,
 
 #ifdef PNG_sRGB_SUPPORTED
 PNG_INTERNAL_FUNCTION(int,png_colorspace_set_sRGB,(png_const_structrp png_ptr,
-   png_colorspacerp colorspace, int intent, int preferred), PNG_EMPTY);
+   png_colorspacerp colorspace, int intent), PNG_EMPTY);
+   /* This does set the colorspace gAMA and cHRM values too, but doesn't set the
+    * flags to write them, if it returns false there was a problem and an error
+    * message has already been output (but the colorspace may still need to be
+    * synced to record the invalid flag).
+    */
 #endif /* sRGB */
 
 #ifdef PNG_iCCP_SUPPORTED
@@ -1459,14 +1467,15 @@ PNG_INTERNAL_FUNCTION(int,png_icc_check_tag_table,(png_const_structrp png_ptr,
    png_colorspacerp colorspace, png_const_charp name,
    png_uint_32 profile_length,
    png_const_bytep profile /* header plus whole tag table */), PNG_EMPTY);
-PNG_INTERNAL_FUNCTION(int,png_icc_set_gAMA_and_cHRM,(
+PNG_INTERNAL_FUNCTION(void,png_icc_set_gAMA_and_cHRM,(
    png_const_structrp png_ptr, png_colorspacerp colorspace,
    png_const_charp name, png_const_bytep profile, uLong adler), PNG_EMPTY);
    /* 'adler' is the Adler32 checksum of the uncompressed profile data. It may
     * be zero to indicate that it is not available.  It is used, if provided,
-    * as a fast check on the profile when checking to see if it is sRGB.  The
-    * result is false only if an error is detected in the profile; the routine
-    * may return true without actually setting cHRM and gAMA values.
+    * as a fast check on the profile when checking to see if it is sRGB.
+    * The routine may not set gAMA or cHRM if there are problems in the profile,
+    * however none of these problems are fatal (the profile has already been
+    * checked.)
     */
 #endif /* iCCP */
 
@@ -1598,6 +1607,21 @@ PNG_INTERNAL_FUNCTION(void,png_app_error,(png_const_structrp png_ptr,
 #  define png_app_error(pp,s) png_error(pp,s)
 #endif
 
+PNG_INTERNAL_FUNCTION(void,png_chunk_report,(png_const_structrp png_ptr,
+   png_const_charp message, int error),PNG_EMPTY);
+   /* Report a recoverable issue in chunk data.  On read this is used to report
+    * a problem found while reading a particular chunk and the
+    * png_chunk_benign_error or png_chunk_warning function is used as
+    * appropriate.  On write this is used to report an error that comes from
+    * data set via an application call to a png_set_ API and png_app_error or
+    * png_app_warning is used as appropriate.
+    *
+    * The 'error' parameter must have one of the following values:
+    */
+#define PNG_CHUNK_WARNING     0 /* never an error */
+#define PNG_CHUNK_WRITE_ERROR 1 /* an error only on write */
+#define PNG_CHUNK_ERROR       2 /* always an error */
+
 /* ASCII to FP interfaces, currently only implemented if sCAL
  * support is required.
  */