Sorry, I forgot to add a subject! Am 05.11.2006 um 08:35 schrieb Mike Fischer:
Hi!
I am seeing a strange problem with transparent PNG files in the release version of Safari/WebKit on Max OS X 10.4.8 PPC:
I created a 1 pixel PNG image with color white and an alpha value of approx. 60%.
When I display this in an IMG tag (or as a CSS background image) over other content the other content does not appear lighter as expected but more gray (not really darker).
When I use a CANVAS element to draw a white fill color with 60% alpha the background is lightened as expected.
The current nightly build does not show this problem. By searching for bugs related to PNG on <http://bugs.webkit.org> I couldn't find anything relevant. Also Firefox 1.5.0.7+, Opera 9.02 and OmniWeb 5.5.1 show the expected color effect, i.e. lightening the background.
OTOH using a 1 pixel PNG with color black and an alpha of 50% works exactly as expected, i.e. darkening the background for a shadow effect.
My questions:
a) Was there a bug in WebKit causing this that got fixed for the current nightlies? Or is this some unintended side effect and I need to file a new bug to ensure that this stays fixed in the future?
b) Is there a workaround for the released version of WebKit (419.3)? (Other than using a CANVAS element ;-)
A test page demonstrating the effect is here (the top transparent area shows the problem): <http://home.fi-works.de/test/test-png-alpha.html> Note that the testing area is built using JavaScript DOM methods in this example. It essentially builds three layers: At the bottom some text is created. Then (DIV id:"bgc1" z.index:1) some color areas are created and in the top layer (DIV id:"bgc2" z-index:2) the transparent testing areas are created.
Thanks! Mike -- Mike Fischer Softwareentwicklung, EDV-Beratung Schulung, Vertrieb Web: <http://homepage.mac.com/mike_fischer/index.html>
-- Mike Fischer Softwareentwicklung, EDV-Beratung Schulung, Vertrieb Web: <http://homepage.mac.com/mike_fischer/index.html>