CompressedImageSaver revamp by JMS55 · Pull Request #23567 · bevyengine/bevy

JMS55 · 2026-03-29T02:15:56Z

Objective

Provide a higher quality texture compressor
Automatically generate mipmaps

Closes #14671.

Solution

Use the ctt crate

Testing

New compressed_image_saver example (for now I have merged the textures into this branch, but before merging we should place them in the bevy asset repo)

Showcase

beicause · 2026-04-01T12:35:10Z

FYI I'm working on a basisu asset processor in beicause/bevy_basisu_loader#33

…ed-image-saver2

cwfitzgerald · 2026-04-12T16:14:55Z

+            return Err(CompressedImageSaverError::UninitializedImage);
+        };
+
+        if image.texture_descriptor.mip_level_count != 1 {


Note ctt can deal with any source amount of mips

cwfitzgerald · 2026-04-12T16:15:38Z

+                    stride: image.width() * bytes_per_pixel,
+                    format: input_format,
+                    color_space,
+                    alpha: ctt::AlphaMode::Straight, // TODO: User-configurable?


Yeah this should be user configurable.

cwfitzgerald · 2026-04-12T16:16:13Z

+            container: ctt::Container::Ktx2,
+            quality: ctt::Quality::default(),
+            output_color_space: None,
+            output_alpha: None,


The correct default here is Some(premultiplied), though should be user configurable

andriyDev

Overall LGTM. We're just calling another lib!

I haven't tested this locally, but the code looks fine (barring one complaint).

andriyDev · 2026-04-12T17:56:29Z

+        })
+    }
+
+    #[cfg(feature = "compressed_image_saver_universal")]


I am really not a fan of this. Saying we just straight up can't compile either case if both features are enabled kinda sucks.

WDYT about just having two CompressedImageSavers? CompressedImageSaverCtt and CompressedImageSaverUniversal? Then just pick one in the plugin? This way if users want to use the old compression, they can. You could also have a wrapper CompressedImageSaver for compatibility (which internally holds one of the backends), so that we keep old meta files working.

I am personally not a fan of mutually exclusive feature flags, since it means I can't just test with --all-features.

Generally the idea was that you'd always be using CompressedImageSaver (same meta files), and then depending on what platform you want to target, you'd enable different backends.

I think you can use feature gate within a custom asset processor instead of asset savers, instead of using LoadTransformAndSave.

I want to double down on this. I think we should support both. I'd rather users have the capacity to remix these however they want in their own processors, rather than being limited to whatever processors we give them.

andriyDev · 2026-05-03T17:53:05Z

@@ -20,6 +20,7 @@ Cargo.lock

 # Bevy Assets
 assets/**/*.meta


I think we could remove this now that we don't auto generate meta files, but let's not do that in this PR.

alice-i-cecile · 2026-05-03T19:47:10Z

+    fn default() -> Self {
+        Self {
+            input_alpha_mode: AlphaMode::Straight,
+            output_alpha_mode: AlphaMode::Premultiplied,


This is a surprising default to me. Why are we changing this on users in the default config?

If I hand an image processor an image. I expect nothing else to be changed during processing. Why do we expect Straight in but return PMA out?

I don't know what the correct API design is for bevy, however if any kind of blending is involved, you need premultiplied alpha for the math to work out. iff you are nearest sampling you can do the premultiplication in the shader, but if you're doing any kind of linear sampling you need premultiplied alpha in the texture.

Yeah, this is generally the best default for users.

alice-i-cecile

We need to move the assets out into the bevy-assets repo still 🙂

I've also caught a few smaller problems, which should be addressed.

beicause · 2026-05-04T05:14:54Z

for now I have merged the textures into this branch, but before merging we should place them in the bevy asset repo

@alice-i-cecile I think this is merged too quickly. The assets have not moved to bevy asset repo. Even if we delete these files later, the git history is permanently bloated unless you force push to rewrite history.

JMS55 added 2 commits March 28, 2026 22:15

WIP

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JMS55 added the A-Assets Load files from disk to use for things like images, models, and sounds label Mar 29, 2026

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JMS55 added 7 commits March 28, 2026 22:57

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Disable selector RDO for linear, based on tune_for_normal_maps

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Misc

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Assert

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alice-i-cecile added C-Usability A targeted quality-of-life change that makes Bevy easier to use S-Waiting-on-Author The author needs to make changes or address concerns before this can be merged labels Mar 29, 2026

Merge commit '842fa5c4559303edbd1774013bc0f3d0dd529799' into compress…

73d0687

…ed-image-saver2

beicause mentioned this pull request Apr 8, 2026

Replace basis-universal-rs with basisu_c_sys to improve basis universal support #23672

Open

JMS55 added 7 commits April 12, 2026 09:47

Merge commit '6dc30ca38789a1023df17649198b006e1df9cf5c' into compress…

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…ed-image-saver2

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cwfitzgerald reviewed Apr 12, 2026

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JMS55 added 2 commits April 12, 2026 12:31

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Comment thread _release-content/migration-guides/compressed_image_saver.md Outdated

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Comment thread crates/bevy_image/src/compressed_image_saver.rs Outdated

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JMS55 requested a review from andriyDev May 3, 2026 17:29

Clippy

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andriyDev approved these changes May 3, 2026

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User-configurable alpha modes, clippy

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Comment thread crates/bevy_image/src/image_texture_conversion.rs

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JMS55 added 3 commits May 3, 2026 22:28

Require zstd

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Alpha mode rename

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Merge branch 'main' into compressed-image-saver2

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alice-i-cecile approved these changes May 4, 2026

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alice-i-cecile added S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it and removed S-Needs-Review Needs reviewer attention (from anyone!) to move forward labels May 4, 2026

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Merged via the queue into bevyengine:main with commit 3f9bd6b May 4, 2026
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JMS55 commented Mar 29, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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beicause commented Apr 1, 2026

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beicause commented May 4, 2026

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JMS55 commented Mar 29, 2026 •

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