[Interest] QImageIOWriter for multi-framed images

[Scott Bloom]

I have everything working, for Qt5 writing out static GIF.  I can also write out a multi-framed gif, with varying delays outside the QImage system.

The only issue, is QImageIOWriter simply doesn't have support for multi-framed gif files like QImageIOReader does.

Ive looked into the code, and following the same architecture (using the same variables/attributes) and simply having 1 QImage written after another works, the only issue is for GIF (and others) you also have to have a reference to the previous frame.  Reading doesn't require this

Scott

From: Mitch Curtis <mitch.curtis at qt.io>
Sent: Monday, January 3, 2022 3:43 AM
To: Scott Bloom <scott at towel42.com>; interest at qt-project.org
Subject: RE: QImageIOWriter for multi-framed images

For what it's worth, there is a task in Jira for being able to write GIFs:

https://bugreports.qt.io/browse/QTBUG-64889

From: Interest <interest-bounces at qt-project.org<mailto:interest-bounces at qt-project.org>> On Behalf Of Scott Bloom
Sent: Monday, 20 December 2021 9:20 PM
To: interest at qt-project.org<mailto:interest at qt-project.org>
Subject: [Interest] QImageIOWriter for multi-framed images

QImageIOReader supports multi-framed images for QMovie.

However, there doesn't seem to be any support in the writer for supporting such images. I checked 5.15.7 and the docs in Qt6 as well.

Is there a plan for this in the works in the future?

Most of the read relies on the IO Handler supporting it.  But for the writer, the handler only gets the single frame QImage itself, not the multiple frames.

Am I missing something?  I don't get access to the original/source multi-framed IO handler, so Im not sure how to add this functionality as a plugin at all.

For some context, there is a format call BIF, which comes from ROKU (streaming video etc) which represents frames from a video stream at various points.  Players use this format as a compressed version of the movie so when you use the mouse over various points on the players timeline, it can show the "frame".  Typically its once every 10 seconds, between scaling of the image and this allows a 2 hour movie that's 10gigs in 2160p h265 encoding, to be represented in 6megs of data or so.

I already have created the QImageIOReader for BIF so I can view the file using QMovie.  Pretty straightforward.

However, I would like to be able to load a multi frame GIF and save it as  BIF and vice versa.  I already have the Multi-Frame GIF writer done as a stand alone class.  So I can feed it multiple QImage's with a delay and it writes out a functional gif movie.  However, I would like to make this a IO Plugin writer for GIF writing only.

Any ideas?

Scott
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