Mozilla currently uses a 2D tiling scheme for displaying interlaced PNG images. The libpng docs describe a different approach, the "sparkle" effect, where the image pixels are just display in their final locations as they arrive. The image seems to just grow in place. The libpng docs do not like the sparkle method but I don't like the tiled method because the incoming image appears to move up and to the left as more of it arrives. Maybe mozilla should support both. A user pref would be nice. Maybe, even, a web page could eventually select the method. Just an idea.
Bah. Implementing the `sparkle effect' would take us back to the bad old days of 1995, when Mozilla/0.91 and earlier did this for interlaced GIFs. And a user pref for it would incite rage from those who accuse Mozilla of being bloated, and they'd be right. If you don't like the image appearing to move up and/or to the left with the tiled method -- which is a reasonable complaint -- then file an RFE for each tile (except the tiles on the edge of the image) to be centered around the downloaded pixel, rather than having its top left corner on the downloaded pixel.
Who mentioned GIFs? I didn't. This is about 2D interlacing. You don't like it; I do. That's nice.
> Who mentioned GIFs? I did. That's why the comment says `Additional comments from Matthew Thomas (mpt)' at the top. > This is about 2D interlacing. As used by both PNGs and GIFs. There's no good reason for them to behave differently.
But a 1D sparkle would probably have a venetian blind effect. Hard to say if it looks good. There's no reason why 1D and 2D interlacing has to be the same.
All pnunn bugs reassigned to Pav, who is taking over the imglib.
Assignee: pnunn → pavlov
Status: ASSIGNED → NEW
The best method as far as I can tell is the interpolated approach. This has the effect of starting off looking blurry and coming into focus as the image loads. This method makes text in the image readable earlier in the download process than the other methods. O'Reilly's "PNG: The Definitive Guide" talks about it and shows a side-by-side comparison.
<URL:http://www.its.caltech.edu/~stl/png.html> has some nice images of PNGs being showed with a) bicubic interpolation, b) bilinear interpolation, c) no interpolation. As you can see, it's much easier to see what the image is about when using bicubic interpolation, even when only 1/64 of it is downloaded. I think interpolation (preferably bicubic) would be the best way to display adam7 PNGs.
Bilinear/cubic interpolation should be filed as a separate bug (which would be much more likely to be fixed than this bug would).
Bicubic interpolation is now bug #75941.
> Bicubic interpolation is now bug #75941. No, it's bug #75077. Sorry for not mentioning that I had filed this bug.
Summary: Implement the "sparkle" effect → [RFE]Implement the "sparkle" effect
Swapping URL for archive.org
Talked with Joe, marking as wontfix.
Status: NEW → RESOLVED
Last Resolved: 8 years ago
Resolution: --- → WONTFIX
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