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https://github.com/storytold/craft-libs.git
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Dylan M. Taylor
ee78a9bd46
PhotoCraft's `photocraft-psd` crate (crates/psd at storytold/photocraft 63b641b55e54bf8f5c83efd977fdb16a2c255431) as `craft-psd`: the lossless PSD/PSB model, reader, writer and builder, descriptors, the Photoshop resource files that share its primitives (.abr, .asl, .aco, .act, .ase, .grd, .pat, .atn, .csh, .shc) and the Photoshop blocks of a layered TIFF. The crate had no dependency on any other PhotoCraft crate. Code is unchanged apart from the crate name, craft-libs' rustfmt width, comments that named other PhotoCraft crates, issue references (now `photocraft#N`), and the corpus tests' directory (`CRAFT_PSD_CORPUS` or `corpus/` at the workspace root). Tests, proptests, fuzz targets and fixtures move with it. Part of #778, #786.
94 lines
3.4 KiB
Rust
94 lines
3.4 KiB
Rust
//! HDR toning settings: the Color Mode Data of 32-bit-per-channel documents.
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//!
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//! Adobe's specification only documents the Color Mode Data section for
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//! indexed and duotone images, but every 32-bit file Photoshop saves carries
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//! an `hdrt` record there (the defaults of Image › Mode › 8/16 Bits/Channel ›
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//! HDR Toning), and current versions append an `hdra` record. Photoshop 2026
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//! refuses to open a 32-bit file whose Color Mode Data is empty or not in this
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//! form ("the open options are incorrect", photocraft#291), so writers must emit it.
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//!
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//! The layout below was established by observing Photoshop-saved files (the
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//! PhotoCraft corpus oracles); fields whose meaning is not known are written
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//! with the values Photoshop writes for a new document.
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use crate::io::WriteExt;
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/// Key of the HDR toning record.
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pub const TONING_KEY: &[u8; 4] = b"hdrt";
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/// Key of the record current Photoshop versions append after the toning record.
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pub const EXTRA_KEY: &[u8; 4] = b"hdra";
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/// `true` if `data` (a file's Color Mode Data) starts with an HDR toning record.
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pub fn is_toning_data(data: &[u8]) -> bool {
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data.starts_with(TONING_KEY)
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}
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/// The Color Mode Data Photoshop writes for a new 32-bit document: a version 3
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/// `hdrt` record (method 2, preset "Linear", an identity toning curve) followed
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/// by a version 6 `hdra` record. 110 bytes.
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pub fn default_toning_data() -> Vec<u8> {
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let mut out = Vec::with_capacity(110);
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// `hdrt`, version 3.
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out.put(TONING_KEY);
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out.put_u32(3);
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out.put(&0.23f32.to_be_bytes());
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out.put_u32(2); // toning method
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// Preset name: Unicode string (UTF-16 code units including the terminator).
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let name: Vec<u16> = "Linear".encode_utf16().chain(std::iter::once(0)).collect();
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out.put_u32(name.len() as u32);
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for u in name {
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out.put_u16(u);
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}
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// Toning curve: two points, (0, 0) and (255, 255), both corners.
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out.put_u16(2);
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out.put_u16(2);
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for (input, output) in [(0u16, 0u16), (255, 255)] {
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out.put_u16(output);
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out.put_u16(input);
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}
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out.put(&[1, 1]);
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out.put(&[0; 8]);
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out.put(&16.0f32.to_be_bytes());
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out.put_u32(1);
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out.put_u32(0);
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out.put(&1.0f32.to_be_bytes());
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// `hdra`, version 6.
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out.put(EXTRA_KEY);
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out.put_u32(6);
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out.put_u32(0);
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out.put(&20.0f32.to_be_bytes());
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out.put(&30.0f32.to_be_bytes());
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out.put_u32(0);
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out.put_u32(0);
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out.put(&1.0f32.to_be_bytes());
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out.put(&[0; 6]);
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out
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}
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/// The Color Mode Data a writer should emit for a file of `depth` bits per
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/// channel when it has nothing of its own to keep: the default HDR toning
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/// records for 32-bit files, nothing otherwise (indexed and duotone data come
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/// from the document).
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pub fn color_mode_data_for_depth(depth: u16) -> Vec<u8> {
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if depth == 32 { default_toning_data() } else { Vec::new() }
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn default_record_layout() {
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let d = default_toning_data();
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assert_eq!(d.len(), 110);
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assert!(is_toning_data(&d));
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assert_eq!(&d[72..76], EXTRA_KEY);
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// Version fields.
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assert_eq!(&d[4..8], &3u32.to_be_bytes());
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assert_eq!(&d[76..80], &6u32.to_be_bytes());
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assert!(color_mode_data_for_depth(8).is_empty());
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assert!(color_mode_data_for_depth(16).is_empty());
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assert_eq!(color_mode_data_for_depth(32), d);
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}
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}
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