refactor(mobile): Use ImmichThumbnail and local thumbnail image provider

[martyfuhry]

• Makes a new ImmichThumbnail with image providers
• New ImmichLocalThumbnailProvider for showing local thumbnails
• Loads low resolution thumbnail in multipart loading (need to test the usefulness of this)
• Adds blur effect to thumbnail previews in gallery mode
• Changes custom image provider type to be their own class
• Adds blurhash (Closes feat(mobile): Adds blurhash #7055 )

Blurhash

Thumbnail preview

Without blur / With blur

Also might add in cache for remote images in this one.

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[martyfuhry]

That blur is a bit aggressive, maybe it could be taken down a bit? It's difficult to find the "right value" which reduces the sharpness of the pixelated version without making it look blurry.

[shenlong-tanwen]

Suggested change

	fadeInDuration: const Duration(milliseconds: 100),
	fadeInDuration: duration,

[martyfuhry]

Thank you, I missed this!

[shenlong-tanwen]

Why do we need this to be a state? Can we use useRef instead?

[martyfuhry]

Didn't know the difference! Thanks for the suggestion. I've made the change, and I think it'll be very helpful.

[shenlong-tanwen]

LGTM! Love the ImageProvider related PRs <3

[alextran1502]

Hi @martyfuhry, I just tested this PR, and here are a few thoughts.

• When dragging across the timeline, I found the gradient placeholder is more prominent than the blur hash image. I wonder if the gradient placeholder should be replaced entirely by the blurhash.
• If the point above cannot be solved, I found the transition from the gradient -> blurhash -> actual image is very fast. I don't see the need to add blurhash and increase the complexity.

I think my point is to try to keep the complexity down if we can when the trade-off is minimal. Let me know what you think

[fyfrey]

Hi @alextran1502

we can't show the blurhash while drag scrolling because we don't load the asset information. We only fetch this information from the database once drag scrolling stops.

The transition is indeed very fast for cached thumbnails. For non-cached images it makes a lot of sense, though. We can probably improve this in the future to only use the blurhash if the image is not cashed

[martyfuhry]

Google photos doesn't show a blurhash at all on my device. I agree it is very very fast and may appear too busy. We could replace the placeholders entirely with blurhashes if we can query the assets while scrubbing quickly enough to read their blurhash.