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Codecs: save Cineon (.cin) film frames

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Write Kodak Cineon 4.5: the 1024-byte generic header (V4.5, one or three
channels designated gray or R/G/B, 10 bits, code values 0-1023 over
densities 0-2.048) and a 1024-byte film header left undefined, then the
samples three to a big-endian 32-bit word, left justified (packing 5),
lines on a word boundary. Samples are written as round(v * 1023 / 65535),
so a frame opened from Cineon saves back with its code values; other
images take the encode plan (alpha dropped, CMYK and Lab to RGB) and are
quantized to 10 bits.

Cineon leaves ASYMMETRIC_EXCEPTIONS, Save As offers .cin, and the codecs
README, file-format parity and G10 are updated.
This commit is contained in:
Marco Arnulfo
2026-10-15 20:41:58 +02:00
parent 5f9190f8cc
commit b11223b272
10 changed files with 197 additions and 20 deletions
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crates/codecs/README.md
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@@ -47,7 +47,7 @@ let out = encode(&img, Format::Tiff, &EncodeOptions::default())?;
| Radiance HDR | yes | yes | F32 | RGB | no | no | no | no | no | no | yes (RGBE) | `image` |
| FITS | yes | yes | U8, U16, F32 | Gray, RGB | no | no | no | no | no | yes (header cards) | no | built in |
| DPX | yes | yes | U8, U16 (10/12-bit code values read and written exactly through U16) | Gray, RGB, RGBA | yes | no | no | no | no | DPX header fields only (creator, project, copyright, creation time, transfer, colorimetric, frame position, frame rate, time code) | no | built in |
| Cineon | yes | **no** | U16 (10-bit code values) | Gray, RGB | no | no | no | no | no | no | n/a | built in |
| Cineon | yes | yes | U16 (10-bit code values read and written exactly through U16) | Gray, RGB | no | no | no | no | no | no | no | built in |
| AVIF | **no** | only with feature `avif` | U8 | RGB, RGBA | yes | no | no | no | no | no | yes | `image` + `ravif` |
| HEIF/HEIC | with feature `heif` | **no** | U8, U16 (10/12-bit decodes to U16) | RGB, RGBA | yes (auxiliary alpha) | yes (`colr` prof) | yes | yes | no | no | n/a | `heic-rs` |
@@ -96,13 +96,18 @@ embedded table (and a PNG's transparent entry) so `photocraft-io` can open them
Other descriptors, signed or run-length-encoded data and other bit depths return
`CodecError::Unsupported` naming the field.
* **Cineon (read-only).** Kodak's 10-bit logarithmic film-scan format (the one DPX grew from),
* **Cineon.** Kodak's 10-bit logarithmic film-scan format (the one DPX grew from),
read from the same Kodak header family: the generic 1024-byte header, big-endian, one (Gray)
or three (RGB) channels, three 10-bit samples packed into each 32-bit word, lines on a word
boundary. The 10-bit code values open as U16 `round(c × 65535 / 1023)`; the file's black/white
reference points are a log-conversion choice and are not applied. A depth other than 10 bits or
a channel count other than 1/3 returns `CodecError::Unsupported`; truncation errors rather than
panicking. There is no Cineon writer (`ASYMMETRIC_EXCEPTIONS`); save as DPX, TIFF or EXR.
panicking. Writing follows the Cineon 4.5 layout: a 1024-byte generic header (version `V4.5`,
one or three channels designated as universal-metric gray or R, G, B, 10 bits, data 0–1023 over
densities 0–2.048) and a 1024-byte film header left undefined, then the samples three to a
big-endian 32-bit word, left justified (packing 5), lines on a word boundary. Samples are written
as `round(v × 1023 / 65535)`, so a frame opened from Cineon keeps its code values; any other
image takes the encode plan (alpha dropped, CMYK and Lab to RGB) and is quantized to 10 bits.
* **Camera raw files** (DNG, CR2, NEF, ARW… which are TIFF-structured) are recognised and refused
with `CodecError::Unsupported`: they are sensor data, not flat images. `photocraft-raw` decodes