PNG Support
The following tests were meant to demonstrate the support levels of PNG-8 and PNG-24 respectively amongst 2003's browsers. These tests have an accompanying write-up.
PNG-8
 32 colour GIF, saved from |
 32 colour PNG, saved from |
above image on white background |
above image on white background |
If your browser supports PNG-8 properly, what you should see are two identical coffee cups on a blue background in the top row, and the same two coffee cups on a white background in the bottom row. All images contain a 1-bit transparency channel, the left column being GIF, the right PNG. If your browser displays the bottom right cup with a blue background, or the top right cup with anything but a blue background, then it does not support PNG-8 transparency. If the right column images are missing, then it does not support the PNG format.
List of known browsers that pass the test: IE5+/Win, Mozilla 1.0+/Win, Netscape 6+/Win, Safari Beta v74 (Mac), Netscape 7/Mac, IE 5.2/Mac, Camino 0.7/Mac.
PNG-24
 256 colour GIF, saved from |
 True colour PNG, saved from |
above image on white background |
above image on white background |
If your browser supports PNG-24 properly, what you should see are two identical coffee cups with drop shadow on a blue background in the top row, and the same two coffee cups on a white background in the bottom row.
You will notice the cups on the left (GIF) dither to blue, leaving a fringe that looks out of place on the white background. This highlights the limitation of single-bit transparency. A pixel can either be completely transparent, or completely opaque. Proper planning is required ahead of time to compensate for any background colours or patterns.
If your browser supports proper PNG-24 alpha transparency, you will see that the images on the right fit properly onto the two backgrounds colours. If not, they will most likely dither to a solid grey background colour. This highlights both the strength of a full 8-bit alpha channel, and the limitations of some of today's browsers.
List of known browsers that pass the test: Mozilla 1.0+/Win, Netscape 6+/Win, Safari Beta v74 (Mac), Netscape 7/Mac, IE 5.2/Mac, Camino 0.7/Mac.
