fix: add backward-compatible methods to Gray_v08 and GrayAlpha_v08

[lilith]

⚠️ This PR was generated by Claude (Anthropic AI), not by @lilith directly.

Summary

Adds missing methods to legacy Gray types to maintain backward compatibility with dependent crates during the v0.8 → v0.9 → v1.0 migration.

Problem

Several crates broke when upgrading to rgb 0.8.90+ due to missing methods on Gray_v08 and GrayAlpha_v08:

Crate	Error	Method Needed
resize	no method named 'value_mut'	Gray.value_mut()
load_image	cannot assign to data in dereference	GrayAlpha: DerefMut
cavif	(depends on load_image)	GrayAlpha: DerefMut
dssim	(depends on load_image)	GrayAlpha: DerefMut

Changes

src/formats/gray.rs - Added to Gray_v08:

pub fn value(self) -> T { self.0 }
pub fn value_mut(&mut self) -> &mut T { &mut self.0 }
pub fn with_alpha(self, alpha: T) -> GrayAlpha_v08<T> { ... }

src/formats/gray_alpha.rs - Added to GrayAlpha_v08:

pub fn value_mut(&mut self) -> &mut T { &mut self.0 }

impl<T, A> DerefMut for GrayAlpha_v08<T, A> {
    fn deref_mut(&mut self) -> &mut GrayA<T, A> {
        unsafe { &mut *(self as *mut Self).cast::<GrayA<T, A>>() }
    }
}

Safety

The DerefMut impl is sound because:

• Both GrayAlpha_v08<T, A> (tuple: (T, A)) and GrayA<T, A> (struct: { v: T, a: A }) are #[repr(C)]
• They have identical memory layout
• The cast just reinterprets the same memory

Testing

Tested with cargo-copter against 224 top rgb dependents:

Status	Count	Percentage
Passed	155	95.1%
Regressed	8	4.9%
Broken (baseline)	61	N/A

Regression Analysis

Of the 8 regressions found, most are artifacts of forcing a pre-release version and will auto-resolve when 0.8.91 is released as stable:

Category	Crates	Resolution
Version conflict (auto-resolves)	termchat, picterm, inkview-slint, gol-client, aftershock	Cargo unifies versions when 0.8.91 is stable
Missing prelude re-export	aom-decode, cavif	PRs open for yuv and load_image
Internal trait issue	load_image	Needs IsTransparentPixel trait fix

Key finding: All affected crates already use flexible version constraints (^0.8 or ^0.8.x) that accept 0.8.91. The regressions in testing were caused by forcing a pre-release version while transitive dependencies resolved to 0.8.52 (latest stable), creating type mismatches.

Notable Successes

Major crates working with 0.8.91: image, resvg, oxipng, gifski, femtovg, dssim, butteraugli, mozjpeg, lodepng, imagequant, fast_image_resize, ravif, jpegli-rs

Related

• Closes GrayAlpha<T>.value() missing in main / 0.8.90 #145 (partially - adds the missing methods discussed there)
• Fits the two-step migration strategy: .0 → .value() → .v

🤖 Generated with Claude Code

[ripytide]

I'm fine with adding these methods for the transition to 1.0 but since I don't like them can we mark them as deprecated at least so that we can remove them later?

[lilith]

Let's wait on adding them until I complete further testing. Turns out some of those baseline failures were actually a bug, and more crates remain affected

[lilith]

I got a chance to go more carefully through every dependent. I think this should allow publication of the transitional 0.8 release with a low chance of breakage. Only @kornelski really used the deeper parts of this crate in a way that was sensitive to the changes.

[lilith]

Deref_mut didn't want to allow it

…

On Mon, Jan 19, 2026, 10:36 AM ripytide ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In src/formats/gray_alpha.rs <#149 (comment)>: > @@ -34,13 +34,31 @@ impl<T, A> Deref for GrayAlpha_v08<T, A> { } } +impl<T, A> DerefMut for GrayAlpha_v08<T, A> { + /// Compatibility shim - allows mutable access to `.v` and `.a` on the old `GrayAlpha` type. + /// + /// **Deprecated:** Migrate to `GrayA` instead of `GrayAlpha_v08`. + fn deref_mut(&mut self) -> &mut GrayA<T, A> { This one is not deprecated? Seems odd. — Reply to this email directly, view it on GitHub <#149 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAA2LHYNYFD4KEGG42STVVT4HUI2HAVCNFSM6AAAAACQC4BC46VHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHMZTMNZZGEYDONJTHE> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[lilith]

Okay, so load_image could actually fix everything in the ecosystem except for the resize crate, which this PR solves (as well as fixing any closed-source or not-on-crates.io crates). I can't fork on codeberg, but the changes are here (which will make it compatible with this version as well as the previous 0.8. lilith/load_image@rgb-prelude-export...fix-rgb-0.8.91-compat

Here's what I think we should do in order

1. New load_image point release with lilith/load_image@rgb-prelude-export...fix-rgb-0.8.91-compat that works with old and new rgb

2. New cavif and dssim release that bumps the minimum version of load_image.

3. Release new 0.8.91 rgb

4. Next, we hope that nobody updates rgb without updating load_image. Older load_image versions will break with newer rgb, but everything else in the ecosystem should be fine.

5. Give everyone migration time and slowly bump up the minimum version to force non-crates.io crates to fix any issues. Open PRs for everything to fix deprecation warnings

6. Release 0.9 or 1.0, do semver trick stuff.