the latter is in fact a 1.2.8 build distributed with GTK+
(as of today, the most recent libpng is 1.2.24).
;;; Set default known names for image libraries
(setq image-library-alist
'((xpm "libxpm.dll" "xpm4.dll" "libXpm-nox4.dll")
- (png "libpng13d.dll" "libpng13.dll" "libpng12d.dll" "libpng12.dll" "libpng.dll")
+ (png "libpng12d.dll" "libpng12.dll" "libpng.dll"
+ ;; these are libpng 1.2.8 from GTK+
+ "libpng13d.dll" "libpng13.dll")
(jpeg "jpeg62.dll" "libjpeg.dll" "jpeg-62.dll" "jpeg.dll")
(tiff "libtiff3.dll" "libtiff.dll")
(gif "giflib4.dll" "libungif4.dll" "libungif.dll")))