it should still fix some issue It is possible to transfer an image from a PNG to a GIF. However, I don't recommend that you do so. The GIF format is substantially less capable than PNG. PNG supports RGBA color channels and partial transparency. GIF uses a 256 color palette and no support for partial transparency. There are many libraries available that will make the best of a bad job and attempt to produce a GIF image that is close to the PNG image, but information will be lost.
PHP wrong result for imagetruecolortopalette with PNG with transparency
may help you . You can do that quite easily in ImageMagick, which is distributed on Linux and is available for Windows and Mac OSX. There are also many APIs other than the command line. Here is how to do it in ImageMagick command line. Input:
convert image.png PNG8:result1.png
convert image.png -background white -flatten PNG8:result2.png