Refactors instantiateImageCodec and decodeImageFromPixels to provide intermediate data about the image width, height, and bytes per pixel. This allows for more fine grained control from Dart, particularly when trying to reason about how or whether to maintain aspect ratio in the targetWidth/targetHeight parameters.
This leaves the existing methods functional by re-implementing them to use the new ImmutableBuffer/ImageDescriptor class.
The ImmutableBuffer class is provided so that callers can avoid copying the image data multiple times if they wish to re-recreate the image descriptor.
Related Issues
Remove the extra `decodedCacheRatioCap` parameter, and the
`_frameBitmaps` member from `Codec`. This means that small looped images
will consume more CPU but prevents us from hitting OOM exceptions based
on trying to render multiple larger images.
Also switch to fDisposalMethod for caching frames.
Previously we looped over every single SkCodec::FrameInfo, tracked its
`fRequiredFrame`, and then saved any frames matching those indeces.
Doing this instead avoids that initialization loop and extra data
structure.
Provide a relative, per-image limit to the amount of memory
that's used to cache decoded image frames. Adds an overridable default
that developers can set to control how much memory images are allowed
to use decoded vs undecoded. The cap is set in flutter/flutter#22452.
Note that required frames are always cached regardless of the ratio cap,
because they're currently necessary for the GIF to animate. Previously
cached unessential frames are not cleared in response to the cache
hitting or exceeding the cap.
Addresses #20998 and #14344.
This is the first step to support animated GIFs: flutter/flutter#204
TBD in following CLs:
* Implement Codec.getNextFrame.
* Add Framework side support to run animations.
