feature *.gif *.jpg *.png colour resolution 8 bits 24 bits 8, 24, or 48 bits grey resolution 8 bits 8 bits 8 or 16 bits transparency 1 level none 256 levels lossy compression no yes no lossless compression yes unused yes patent restrictions yes no no animation yes no no (see MNG)

Unfortunately Java Web Start in JDK 1.5 and earler does not support *.png files for the jnlp <icon image, just *.gif and *.jpg. Support for arrived with JDK 1.6.

You can test your browser’s *.png support. You should see an image of a huge spiky red flower to the right of the table above, with proper fades into the transparent background, with no white halos. IE 5.5 and 6.0 do not show it at all. IE can handle some transparent backgrounds but not others. Netscape 4.79 shows it with a purple background. Netscape 8.0+ shows it correctly. Opera 7.51+ shows it correctly. Mozilla and Firefox display it correctly. See Masker for details. You can also click here and here for more tests.

The *.png file header looks like this:

The ImageInfo class will give you the width and height of *.png images (also *.gif and *.jpg) without loading them. It just read the first few bytes of the file.

When you produce ImageIO png images with transparency, Internet Explorer does not render them properly, however, I have heard that rendering them with palette mode creates images that IE will render correctly.

Here is the code for a program to draw a simple image, then save it as a *.png file.

Learning More

	recommend book⇒PNG: The Definitive Guide
		paperback
	ISBN10:	1-56592-542-4
	ISBN13:	978-1-56592-542-7
	publisher:	O’Reilly
	published:	1999-06-01
	by:	Greg Roelofs
More than you wanted to know about *.png image format. Available to browse free as an ebook.
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