Coil3 and bitmap configs

[saket]

Considering that coil3 uses ImageDecoder on android by default, is the ImageRequest.Builder#bitmapConfig option effectively no-op on API 29 and above?

[colinrtwhite]

It's still used to determine software vs. hardware, but good point we should probably disable decoding with ImageDecoder if bitmap config is set to RGB_565 for instance.

As an aside, I was hoping to avoid these types of discrepancies by only using BitmapFactory, but we ended up using ImageDecoder as it has slightly better IO performance. If we keep running into differences and it becomes tough to maintain it might make sense to reevaluate this.

cc @renovate-bot

[revonateB0T]

Maybe we could set MEMORY_POLICY_LOW_RAM for RGB_565
https://developer.android.com/reference/android/graphics/ImageDecoder#MEMORY_POLICY_LOW_RAM
But seems it is not guaranteed.
Moreover it is not simply "slightly better IO performance", It allow us decode a DirectByteBuffer directly with #1971 which is huge performance improvement.

[saket]

Switching to BitmapFactory for non-8888 config sounds like a good idea to me!