https://github.com/ImageMagick/ImageMagick/issues/1305

diff --git a/coders/png.c b/coders/png.c
index 01af8de27ef6eeea3ab619c09aeb26bffa1c215f..ed08314d52bcfa9744299b02059d4baf33dcdb76 100644 (file)
--- a/coders/png.c
+++ b/coders/png.c
@@ -9030,6 +9030,7 @@ static MagickBooleanType WriteOnePNGImage(MngInfo *mng_info,
      number_semitransparent = 0;
      number_transparent = 0;
 
+     (void) SetImageDepth(image,image->depth,exception);
      for (y=0; y < (ssize_t) image->rows; y++)
      {
        r=GetVirtualPixels(image,0,y,image->columns,1,exception);