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Why Do I See Rendering Artifacts With Transparent Images in OpenZoom?
When I try to display PNG tiles with a transparent background I'm getting weird artifacts (halos) around the images. I've checked that these are not in my tiled images of course, they seem to be getting generated by the MultiScaleImage. I'm going to try to attach an example to this post.
I am just guessing, but I wonder if it could have something to do with that splash image that it puts up from the very low resolution tile prior to the rendering. What I mean is, I've noticed that before rendering the full multiscale image OpenZoom seems to put up a highly scaled low resolution version of one of the images first... I'd (independent of this issue) really like to turn that off.. but now I'm also wondering if that is somehow leaving something composited behind.
To be clear, the artifacts are persistent and they scale with the image as I zoom and drag around.
Any suggestions would be appreciated. Thanks.
I am just guessing, but I wonder if it could have something to do with that splash image that it puts up from the very low resolution tile prior to the rendering. What I mean is, I've noticed that before rendering the full multiscale image OpenZoom seems to put up a highly scaled low resolution version of one of the images first... I'd (independent of this issue) really like to turn that off.. but now I'm also wondering if that is somehow leaving something composited behind.
To be clear, the artifacts are persistent and they scale with the image as I zoom and drag around.
Any suggestions would be appreciated. Thanks.
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Inappropriate?I've dug through the source a bit and as near as I can tell this is just a side effect of the way that openzoom works... It seems that in smooth rendering mode it loads all of the tile layers up to the current layer into the display list... So if I'm understanding correctly, the scaled versions of my tile images going all the way down to 1 pixel are now being scaled up to the full view size and layered on top of one another. So any artifacts in the transparent areas (produced by scaling, anti-aliasing or whatever) are showing through in a kind of halo...
I guess my question is - how does everyone else deal with this? Is anyone using transparent images in tiles in this way?
Pat -
Inappropriate?Pat,
After your first post it was just a suspicion but your second post made it clear: You're using an old version of the OpenZoom SDK. Get the latest version, currently 0.4.2.1, and your problem should be fixed:
http://gasi.ch/blog/openzoom-sdk/
Cheers,
Daniel
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Inappropriate?Daniel,
I'm actually using the trunk from SVN.
Should I be using a branch?
Pat -
Inappropriate?Aaarg! (pulling hair out). I see that you have moved the codebase to github. I have been diligently watching the google code svn repository for any changes.
And yes, version 0.4.2.1 appears to fix the problem. (Curious as to how you addressed it).
I guess I should have tracked your blog... but now that I see you're leaving! Double arg! :)
Well, you've done a fantastic job on this and I hope you'll return when the time is appropriate. We all appreciate your effort on this.
Pat
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