Applied fix for [ 439207 ] Monochrome PNG images come up black

Joel Tesler (jtesler)

A monochrome black and white PNG image comes up all
black. This is referring to a single bit greyscale
pixmap, not a one bit palette pxiamp.

The easiest way to reproduce is to grab
http://www.schaik.com/pngsuite/basn0g01.png and go
into the image sample, and replace horse.png with
this file.

The following patch appears to fix the problem.
However, I do not know what other side effects it
might have.

--- imagpng.cpp~ Fri Jul 6 14:53:33 2001
+++ imagpng.cpp Fri Jul 6 15:17:06 2001
@@ -140,6 +140,8 @@

if (color_type == PNG_COLOR_TYPE_PALETTE)
png_set_expand( png_ptr );
+ if (bit_depth < 8)
+ png_set_expand( png_ptr );

png_set_strip_16( png_ptr );
png_set_packing( png_ptr );


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@17295 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/imagpng.cpp

@@ -188,6 +188,10 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose
     if (color_type == PNG_COLOR_TYPE_PALETTE)
         png_set_expand( png_ptr );
 
+    // Fix for Bug [ 439207 ] Monochrome PNG images come up black
+    if (bit_depth < 8)
+        png_set_expand( png_ptr );
+
     png_set_strip_16( png_ptr );
     png_set_packing( png_ptr );
     if (png_get_valid( png_ptr, info_ptr, PNG_INFO_tRNS))