PNG test comments

Example	Colour depth	Mask type	bKGD	Description
	Any	Alpha	n/a	Your browser is interpreting the alpha channel as a simple mask. In the upper image, the alpha cutoff is 1, ie. 0 is the only 'transparent' value; in the lower image, the cutoff is 128, ie. values < 128 are transparent.
	Any	Alpha	No	The alpha channel is being completely ignored.
	Any	Simple	No	Your browser is using the mask when creating its internal rendering of the image. No mask is used when displaying the image.
	Palette	Alpha	No	Your browser is using the alpha channel as a simple mask when creating its internal rendering of the image. No mask is used when displaying the image.
	Palette	Any	Yes	Your browser is rendering the image, with full alpha, against a background of the colour specified in the bKGD chunk. No mask is used when displaying the image.
	Any	Any	n/a	Some browsers render PNGs against the background colour, possibly taking into account background colours specified within tables, completely ignoring the background image if there is one.

Ideally, a browser will fully utilise the mask or alpha channel of a PNG image when displaying it; for an alpha channel, this means blending it with whatever's already at that position on the or page and completely ignoring the bKGD chunk. Browse and Mozilla are the only browsers which I've seen which do all of this (and Browse got there first).

• The PNG test page
• The PNG transparency test
• How the table on the test page appears in some browsers (>80K of images)