Background

We used external texture to display the images in our flutter app. On the Android platform, we draw the Bitmap onto the SurfaceTexture, and on the iOS platform, we convert the UIImage to CVPixelBufferRef, and finally use the Texture Widget to display the image. We do this mainly based on the following considerations：

1. We hope that any Bitmap or UIImage can be efficiently displayed to flutter app. For example, we need to customize a photo list page, but the native platform API only provide us Bitmap or UIImage as photo.
2. Reuse the native platform image loader. the native image loader, such as Glide on the Android platform and SDWebImage on the iOS platform, have implemented a complete set of caching solutions (memory cache, disk cache) and image decoding solutions. In addition, our CDN cropping optimization is also implemented in the native image loader. We hope that flutter app can directly reuse these capabilities.
3. Compared with ui.Image, the memory of external texture is not managed by GC, we can precisely control the timing of memory release

Use case

We are currently refactoring this solution, we want to let the external texture can benefit from the ImageCache logic.
We hope that ImageCache can no longer dependent on ui.Image, so that we can customize ImageInfo and ImageProvier to cache external texture images in ImageCache.

Proposal

let ImageCache can no longer dependent on ui.Image，then users can cache custom ImageInfo

Related code：

Expected

ImageInfo add a property named sizeBytes, then ImageCache use it.

 sizeBytes = info.sizeBytes; 

Actual

 sizeBytes = info.image.height * info.image.width * 4;