transparency with images and png issues

gwempz
gwempz Community Member Posts: 137

 I saved my images as 8-bit png, but it still had the dreaded gray box.  I gave up and created the graph with fly-ins in flash.  Too many bugs in IE7 for some companies to upgrade just yet...seems it breaks other things.  I agree...what a shame.  Thanks for the help!

gwempz said:I've noticed alot of lectora users running into problems using image transparency. I'm no expert on file types, but I've been developing graphics for the web and now lectora courses for several years. So here's some quick info of images file formats:

.jpg – no transparency support

.gif – can be transparent, but is limited to an index of 256 colors and will have blocky/jagged edges.

.png (8-bit) – very similar to .gif format (supports transparency, uses 256 colors). Most of the time these will be slightly smaller file sizes than gif.

.png (24-bit) – supports 256 layers of transparency. These will blend seamlessly into anything you place them on, and support a ton of color. Big drawbacks though are HUGE file sizes, and the dreaded grey background instead of transparency in IE6.

IE6 grey box bug: ONLY IE6 and earlier versions have problems displaying transparent pngs, and only when they are 24-bit. If you’ve ever had a mysterious grey box in your courses or web pages, this is why. Like most IE problems it should have been forseen, is annoying as hell, and confuses everyone who experience it for the first time.

So you can still use 8-bit png images safely in IE6, and even 24-bit ones using some css hacks. IE7 fixed this problem, and all other modern browsers don’t seem to have this issue. Photoshop allows you to save in either 8 or 24 bit png, I'm not sure about other graphic editing programs.

Note: IE7 still has some color and gamma issues with 24-bit pngs, so be careful.