apng format support

[jurplel]

No description provided.

[sonulohani]

We have apng plugin support in Qt. Here is the source code of the plugin:- https://github.com/Skycoder42/QtApng/tree/master/src/plugins/imageformats/apng

[jurplel]

Yes that is the plan.

[sonulohani]

Hi @jurplel

I am able to load apng file successfully. I can see the png file getting animated. For that we need to compile the plugin and put that in plugins/imageformats folder in Qt SDK directory.

The problem is that QImageReader::supportsAnimation() returns false for apng file. I believe we might need to modify/add this as an issue in the plugin repository.

I thought of removing the QImageReader::supportsAnimation() with QMovie::isValid(). However, it returns true even for normal image file which doesn't have animations. So I replaced it with loadedMovie.isValid() && loadedMovie.frameCount() != 1 and this works fine.

[sonulohani]

Here is the PR:- #325

[jurplel]

Only took a quick look at this but I have no idea how QImageReader::supportsAnimation() could not be working.

https://code.woboq.org/qt5/qtbase/src/gui/image/qimagereader.cpp.html#_ZNK12QImageReader17supportsAnimationEv

QImageReader::supportsAnimation() simply queries `supportsOption(QImageIOHandler::Animation).

https://github.com/Skycoder42/QtApng/blob/master/src/plugins/imageformats/apng/apngimagehandler.cpp#L50

supportsOption is written to return true for QImageIOHandler::Animation (unless this bit of code is invalid in a way I cannot see).

Are you using it with a .apng file extension or a .png file extension? It notes in the readme that it only works with .apng. I am guessing you probably did use an .apng file extension though because it seems to imply that it would not work whatsoever with .png.

[sonulohani]

Hi @jurplel

Yes, youre right. If you see the code changes I am explicitly setting the fomat to apng. This would not work with png files because Qt already has plugin available to support png files. The only way I would see to fix is either use our own image reader which would based on the frames count use png or apng. I will explore more on this.

[jurplel]

I have opened an issue for some of the weirdness: Skycoder42/QtApng#11

[BLumia]

qView/src/qvimagecore.cpp

Line 113 in 8ba016b

imageReader.setDecideFormatFromContent(true);

By looking at the current implementation of qView, I guess the supportsAnimation() issue is related to Skycoder42/QtApng#12 which should be fixed now :)

The size image property is still not correct but it's a different issue of QtApng IMO. (update: and this should be fixed in Skycoder42/QtApng#14)

[jurplel]

Oh, cool!