Support to check if a png has animation about apngproject HOT 8 CLOSED

I guess you want to test if the image is indeed animated via for example QImageReader::supportsAnimation. In that case I could modify the code to return false in case I only detected one frame. I just want to validate that this is how you check if it's animated.

Please notice that this is a very simple png implementation, and does support all features. I recommend to fall back to qts png implementation in case you only detect one frame. And it requires libpng to be available for compilation and when running, as it cannot use the statically linked png implementation of the png plugin.

from apngproject.

The thing is: My knowledge of the png lib is rather limited, I found the implementation somewhere and adjusted it to my needs. I simply don't know how to check the headers, and currently don't have the time to read into it. Thus, I do indead read all frames. However, you are free to create a pull request for that. This goes for static linking, too. It kept it dynamic, simply to have less work.

If your fine with keeping the current approach, I can add the animation check as described before.

from apngproject.

Thank you for your cooperation.

As long as I am reading your current implementation, qapng decodes all the frames at the checking stage, so it is heavily loaded and requires a lighter checking method than checking only headers and tags.

planned implementation (extension png):

1. Specify the file and call QImageReader :: supportsAnimation () to check if there is animation
2. (With animation) Change to format="apng" and use QMovie
3. (No animation) Do not change from format="png" and continue to use QImageReader

It is possible to statically link libpng.lib into the apng.dll plugin.
There is a policy of each developer, there are disadvantages and advantages of whether it is dll or lib, but I prefer static linking because it avoids problems.

I actually use my own qjpeg plugin which used libjpeg-turbo in the application.
However, since plugin formats provided by qt such as 'jpeg' and 'png' as standard are proprietary, we can not use with user defined plugins. In my plugin it's formatted as 'turbojpeg'.

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according to https://wiki.mozilla.org/APNG_Specification

The "default image" is the image described by the standard IDAT chunks, and is the image that is displayed by decoders that do not support APNG.

To be recognized as an APNG, an acTL chunk must appear in the stream before any IDAT chunks. The acTL structure is described below.

So, we only need to check the acTL chunk :)

Then it is a trivial matter whether to link libpng statically or dynamically. Usually you do not have to worry. I will change it on this side and use it.

from apngproject.

That doesn't sound too complicated... But I still wont have time for the next two weeks or so. Create a PR if you want, or wait until then. The simple update with checking the frames I can do today or tomorrow

from apngproject.

The animated check works now. Please note that it will return still "true" if no frames are detected at all (i.e. and invalid image), as this is required for Qt to detect the plugin as movie type.

from apngproject.

With the latest commit (001dd13) I rewrote the plugin to make use of the apng patch for libpng.

I case your system does not use the patched libpng version, I also added a script that downloads libpng sources + patch and compiles both to a static library, which can the be used for compilation.

With the patched apng version, the image is read sequentially, and thus only the first few bytes until the acTL chunk are read. Also, blending, autoloops and more have been improved.

I am going to clean up the code a little more and improve the reading part, and then move the apng plugin to a seperate repository. I will close this issue once this is done.

from apngproject.

And done. Have a look at https://github.com/Skycoder42/qapng. It's the refactored and improved apng plugin. Closing this issue as the plugin is no longer part of this repository. If you have further problems/suggestions, please open a new issue on the new project

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