Preserving transparency in GIF and PNG images

GIF format and PNG-8 format support one level of transparency--pixels can be fully transparent or fully opaque, but not partially transparent. PNG-24 format, on the other hand, supports multilevel transparency, letting you preserve up to 256 levels of transparency in an image.

To preserve background transparency in a GIF or PNG image:

1 Open or create an image that contains transparency, and choose File > Save for Web.

2 In the Save For Web dialog box, select GIF, PNG-8, or PNG-24 as the optimization format.

3 Select Transparency.

4 For GIF and PNG-8 format, decide how you want to treat partially transparent pixels in the original image. You can blend partially transparent pixels with a matte color, or you can create hard-edged transparency. (See Creating background matting in GIF and PNG images and Creating hard-edged transparency in GIF and PNG-8 images.)

Optimizing Images for the Web > Making transparent and matted images > Preserving transparency in GIF and PNG images