feat(image): add ImageMagick-equivalent ops (shave/deskew/colors/colorspace/contrast-stretch/density) #16

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David merged 1 commit from feat/magick-ops into main

2026-05-14 03:31:03 +02:00

David commented

2026-05-14 02:59:32 +02:00

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Native Rust equivalents of six common magick flags, exposed under monkey image:

Subcommand	Magick flag	Notes
`image shave --width N --height N`	`-shave WxH`	Centred crop.
`image deskew [--threshold DEG]`	`-deskew`	Projection-profile angle search over `[-15°, +15°]` in 0.5° steps on a downsampled grayscale copy, then bilinear counter-rotation. `--threshold` default is `1.0` so sub-degree noise detections are ignored.
`image colors --count N`	`-colors N`	NeuQuant via the `color_quant` crate. `N` must be in `2..=256`.
`image colorspace --space gray\|srgb`	`-colorspace`	`gray` uses Rec. 709 luminance; `srgb` is identity.
`image contrast-stretch [--black F] [--white F]`	`-contrast-stretch BLACK%xWHITE%`	Per-channel histogram clip and linear remap to `[0, 1]`.
`image density --dpi DPI`	`-density DPI`	Metadata-only. PNG gets a pHYs chunk (DPI -> pixels-per-metre); JPEG gets its JFIF APP0 density bytes patched after re-encoding. Pixel data is unchanged.

Five of these are pixel transforms on the existing ImageBuf and dispatch through run_filter. colors returns Result (range check) and density operates on paths (no ImageBuf round-trip), so both have explicit dispatch arms.

New dependency: color_quant = "1" (MIT/Apache-2.0).

Unit tests in src/image/magick_ops.rs cover dimensions, parameter validation, gray equalisation, and contrast expansion (10 new tests; full suite 39 passing). End-to-end smoke test against a magick-generated 100x60 line drawing confirmed each subcommand produces correct output dimensions and that monkey image density --dpi 300 round-trips through ImageMagick's identifier as 118.11 ppcm (= 300 DPI).

cargo fmt --check, cargo clippy --all-targets -- -D warnings, cargo build --all-targets, and cargo test all pass on this branch.

Test plan

Confirm Forgejo Check workflow passes for this branch.
Run monkey image shave, deskew, colors, colorspace, contrast-stretch, and density against a real document and visually compare to the equivalent magick invocation.
Confirm a PNG produced by monkey image density --dpi 300 in.png out.png reports 300 DPI in viewers that read the pHYs chunk.
Confirm a JPEG produced by monkey image density --dpi 300 in.jpg out.jpg reports 300 DPI in viewers that read the JFIF density bytes.

Native Rust equivalents of six common `magick` flags, exposed under `monkey image`: | Subcommand | Magick flag | Notes | |---|---|---| | `image shave --width N --height N` | `-shave WxH` | Centred crop. | | `image deskew [--threshold DEG]` | `-deskew` | Projection-profile angle search over `[-15°, +15°]` in 0.5° steps on a downsampled grayscale copy, then bilinear counter-rotation. `--threshold` default is `1.0` so sub-degree noise detections are ignored. | | `image colors --count N` | `-colors N` | NeuQuant via the `color_quant` crate. `N` must be in `2..=256`. | | `image colorspace --space gray\|srgb` | `-colorspace` | `gray` uses Rec. 709 luminance; `srgb` is identity. | | `image contrast-stretch [--black F] [--white F]` | `-contrast-stretch BLACK%xWHITE%` | Per-channel histogram clip and linear remap to `[0, 1]`. | | `image density --dpi DPI` | `-density DPI` | Metadata-only. PNG gets a pHYs chunk (DPI -> pixels-per-metre); JPEG gets its JFIF APP0 density bytes patched after re-encoding. Pixel data is unchanged. | Five of these are pixel transforms on the existing `ImageBuf` and dispatch through `run_filter`. `colors` returns `Result` (range check) and `density` operates on paths (no `ImageBuf` round-trip), so both have explicit dispatch arms. New dependency: `color_quant = "1"` (MIT/Apache-2.0). Unit tests in `src/image/magick_ops.rs` cover dimensions, parameter validation, gray equalisation, and contrast expansion (10 new tests; full suite 39 passing). End-to-end smoke test against a `magick`-generated 100x60 line drawing confirmed each subcommand produces correct output dimensions and that `monkey image density --dpi 300` round-trips through ImageMagick's identifier as `118.11 ppcm` (= 300 DPI). `cargo fmt --check`, `cargo clippy --all-targets -- -D warnings`, `cargo build --all-targets`, and `cargo test` all pass on this branch. ## Test plan - [ ] Confirm Forgejo `Check` workflow passes for this branch. - [ ] Run `monkey image shave`, `deskew`, `colors`, `colorspace`, `contrast-stretch`, and `density` against a real document and visually compare to the equivalent `magick` invocation. - [ ] Confirm a PNG produced by `monkey image density --dpi 300 in.png out.png` reports 300 DPI in viewers that read the pHYs chunk. - [ ] Confirm a JPEG produced by `monkey image density --dpi 300 in.jpg out.jpg` reports 300 DPI in viewers that read the JFIF density bytes.

David added 1 commit

2026-05-14 02:59:32 +02:00

feat(image): add ImageMagick-equivalent ops (shave/deskew/colors/colorspace/contrast-stretch/density)

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Native Rust implementations of six common `magick` flags, exposed under `monkey image`. Five are pixel transforms on the existing `ImageBuf`; `density` is a metadata-only op that writes DPI into the PNG pHYs chunk or patches the JFIF APP0 segment of a re-encoded JPEG, leaving pixel data unchanged. `shave` is a centred crop; `deskew` runs a projection-profile angle search over [-15°, +15°] in 0.5° steps on a downsampled grayscale copy and counter-rotates with bilinear sampling, with a `--threshold` default of 1.0° so trivial sub-degree detections are skipped; `colors` runs NeuQuant via the `color_quant` crate (rejects counts outside 2..=256); `colorspace` supports `gray` (Rec. 709 luminance) and `srgb` (identity); `contrast-stretch` clips a per-channel histogram and linearly remaps to [0, 1]. All five are dispatched through the existing `run_filter` helper except `colors` (fallible) and `density` (path-based). Unit tests cover dimensions, parameter validation, gray equalisation, and contrast expansion; end-to-end smoke testing against a magick-generated input confirms each subcommand produces correct output and that `density --dpi 300` round-trips to the expected pHYs value.