High Quality zoom + GIF = not high quality

[Jou]

Thank you for XnView, I thought nothing could beat AcDsee 5.
And XnView is very nicely adjustable for my likeness of viewing, good work!

The Question (Version 1.91.6 de):
The High Quality Zoom is indeed good and high quality, but not for GIF files?
To be specific:
The comic under
http://www.galactanet.com/comic/76.htm
http://www.galactanet.com/comic/Strip76.gif
gets zoomed up with "nearest neighbor" instead of "high quality".

Another thing:
Since the high quality zoom is slow it makes racing through the picture collection with the mousewheel slow, my suggestion: During high quality zoom calculation xnview should view the result every 64'th line + check for "next picture please" commands like mousewheel or PG-up PG-down then, and skip the rest of the rendering and jump to the next picture if recieved.
You can choose another number (like 32 or 16 so) of course, that is up to your coding decision.

Alternatively: Do a cheap (nearest neighbour) zoom first for quick display and the high quality zoom afterwards for the nice look, optionized of course since not all will like that displaying behaviour.

regards,

Joachim

[Clo]

—> Jou

Hello ! Welcome aboard !

• Since the GIF doesn't support more than 256 colours in that programme (8 BPP),
I don't see how you could get a “High Quality” while zooming GIFS…

• Please, notice that the most viewers display GIF as 256 colours max.,
but such a limitation is not in the original specs. really…

VG
Claude
Clo

[Jou]

Wow, quick reply!

—> Jou
I don't see how you could get a “High Quality” while zooming GIFS…

Treat / convert as truecolor and then use your existing zoom routine?
Just the show-during-resampling-and-allow-skip-to-next-picture-before-finished would make XnView feel a lot faster.

Many other viewers do use high quality (as Lanczos resampling as XnView itself uses) on 65k / 256 / 16 / 1 color pics too, like http://www.faststone.org/FSViewerDetail.htm
Even acdsee does some kind of upsampling of paletted pics, but not very good.

Joachim

[foxyshadis]

Many other viewers do use high quality (as Lanczos resampling as XnView itself uses) on 65k / 256 / 16 / 1 color pics too, like http://www.faststone.org/FSViewerDetail.htm
Even acdsee does some kind of upsampling of paletted pics, but not very good.

Joachim

Xnview only uses lanczos in slide show (where it does it for all images, including gifs), but linear in all other modes, no option to change this. It will use HQ for 8-bit png, though. The reason it's turned off for gif is because animated gifs slowed down horribly when it was on, several bug reports on it, the resizing algorithm used here is slow and presumably not highly optimized. (Bilinear also happens to be somewhat broken - it isn't centered, repeated uses will cause the image to crawl toward the upper-left.)

Bilinear also just plain looks bad on paletted pics to me, anyway. It's what acdsee uses, so you wouldn't expect much better. Probably nothing but EDI with gradient debanding would look decent.