[pbearne]

Implemented 'cwebp' Grunt task to convert images to WebP format. Updated 'precommit:image' task to include 'cwebp:dynamic' ensuring WebP conversion during pre-commit.

Trac ticket: https://core.trac.wordpress.org/ticket/62188

[github-actions]

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Props pbearne, mukesh27, adamsilverstein, lancewillett, desrosj.

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[desrosj]

I agree with the image quality likely being far too low. It seems Core uses 86 as the default for WebP. I think matching that is a good start.

Were there specific reasons for choosing grunt-cwebp over some of the other available options, such as Ayesh/grunt-webp? The former has not been updated in 4 years, but the latter was updated 2 years ago and @Ayesh is an active member of the community, so it may be easier to get any needed updates released.

There's also some additional options such as lossless, and deleteLarger in Ayesh/grunt-webp. I wonder if configuring these would be beneficial as well.

[Copilot]

🟡 Changes recommended

The WebP task uses glob patterns that match no files, writes output to a literal SOURCE_DIR/ directory, and is not triggered by WebP-only changes during pre-commit.

3 open issues

• Fix single-item brace glob for WebP files · New
• Use the source directory variable for WebP output · New
• Trigger image pre-commit task for WebP changes · New

What changed in this PR

This PR adds WebP processing to WordPress’s Grunt-based image workflow and connects it to the image pre-commit task.

Changes:

• Adds grunt-cwebp and its locked dependencies.
• Configures a cwebp:dynamic target for core and theme WebP assets at quality 80.
• Adds the target to precommit:image after image minification.

File	Description
package.json	Adds the grunt-cwebp development dependency.
package-lock.json	Locks the new dependency tree and updates shared dependency metadata.
Gruntfile.js	Configures WebP processing and includes it in the image pre-commit task.

_{Review effort: Balanced}

[lancewillett]

dest: 'SOURCE_DIR' is a literal directory name, rather than the configured source directory. Please correct the output mapping and verify the intended behavior on a second precommit:image run: the current inputs are already WebP files, so repeated lossy re-encoding needs to be avoided. The Grunt and package changes also need refreshing against trunk.

_{AI review · gpt-6}

[Copilot]

🔵 Needs a closer look

The precommit image target repeatedly overwrites existing WebPs with lossy re-encodings, causing cumulative quality loss and unrelated asset changes even when only a PNG is edited.

No open issues 🎉

1 previously missed issue

In code that hasn't changed since last review

Avoid cumulative lossy re-encoding of existing WebP assets

Gruntfile.js:1047

q: 80 performs lossy re-encoding, but this target reads existing WebP files and writes back to the same paths. Because precommit:image runs this target for any image change, even an unrelated PNG edit re-encodes all existing theme WebPs; subsequent runs use the previously compressed output, causing cumulative quality loss and unrelated asset changes. Please use lossless optimization for existing WebPs, or generate lossy outputs from preserved original sources instead of overwriting and reusing them.

3 resolved since last review

• Trigger image pre-commit task for WebP changes
• Use the source directory variable for WebP output
• Fix single-item brace glob for WebP files

_{Review effort: Balanced}

[lancewillett]

Thanks for refreshing this. It's not ready yet:

1. Every CI job fails at npm ci. package.json adds grunt-contrib-imagemin, which r63784 removed, while package-lock.json adds grunt-cwebp. The two files are out of sync ("Missing: grunt-contrib-imagemin@4.0.0 from lock file").
2. The cwebp task never runs. precommit:image still lists only imagemin:core, though the PR description says it adds cwebp:dynamic. And since grunt-cwebp isn't in package.json, the loadNpmTasks loop never loads it.
3. Adding webp to the precommit check runs imagemin:core, which only handles PNG, JPEG and GIF.
4. Wired up, it would degrade the images. It re-encodes the existing .webp files in place at quality 80, so every run loses more quality. I raised this on Oct 31.

There's a simpler path now. r63784 replaced grunt-contrib-imagemin with a local task, tools/imagemin/task.js, built on @napi-rs/image. That library already has Transformer#webpLosslessSync(). Adding WebP to that task would keep the output lossless and reuse its 64-byte threshold to skip trivial rewrites. It also avoids a new dependency: grunt-cwebp was last published in 2022, and cwebp-bin runs an install script to fetch the binary. Would you be up for reworking it that way?

_{AI review · claude-opus-5-5}