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LR-HDR-EXPORT: HDR PNG export as 16-bit Rec. 2020 PQ (cICP, cLLI)

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With HDR output on, a photo edited in HDR exports as a 16-bit PNG with the PQ
curve in Rec. 2020 (SDR white at HDR_REFERENCE_WHITE_NITS), described by a
`cICP` chunk (PNG third edition: BT.2020 primaries, PQ, RGB, full range) and
a `cLLI` content light level chunk (the levels the HDR AVIF records). EXIF,
XMP and print resolution are kept; no ICC profile next to cICP. Photos without
an HDR edit, and HDR edits with HDR output off, export as before.

`codecs::encode_png_pq` sits next to `encode_avif_pq` and takes the same
input. Follow-up to #646, ported from #466.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
JordyUSA
2026-10-11 12:46:27 +07:00
co-authored by Claude Opus 5.5
parent 0ba118de92
commit cbc0e2d7db
9 changed files with 147 additions and 13 deletions
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crates/engine/src/export.rs
+14 -6
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@@ -602,8 +602,9 @@ pub struct ExportOptions {
pub bit_depth: Option<u8>,
/// HDR output for photos edited in HDR: JPEG as an ISO 21496-1 gain map JPEG (the SDR
/// rendition plus a gain map, so the file looks right everywhere; quality as set, `limit_kb`
/// not applied), AVIF as 10-bit Rec. 2020 PQ, 32-bit float TIFF with the highlights above SDR
/// white kept. Other formats, and photos without an HDR edit, are SDR.
/// not applied), AVIF as 10-bit Rec. 2020 PQ, PNG as 16-bit Rec. 2020 PQ (`cICP`), 32-bit float
/// TIFF with the highlights above SDR white kept. Other formats, and photos without an HDR
/// edit, are SDR.
pub hdr: bool,
}
@@ -995,6 +996,7 @@ impl ExportOptions {
pub fn effective_depth(&self) -> OutputDepth {
match (self.format, self.bit_depth) {
(ExportFormat::Jpeg | ExportFormat::Webp | ExportFormat::Original | ExportFormat::Dng, _) => OutputDepth::U8,
(ExportFormat::Png, _) if self.hdr => OutputDepth::F32Hdr,
(ExportFormat::Png, Some(16 | 32)) => OutputDepth::U16,
(ExportFormat::Png, _) => OutputDepth::U8,
(ExportFormat::Tiff, Some(8)) => OutputDepth::U8,
@@ -1018,15 +1020,20 @@ impl ExportOptions {
}
/// Whether these options write HDR files (for photos edited in HDR): JPEG (gain map), AVIF
/// (PQ) or 32-bit float TIFF with [`ExportOptions::hdr`].
/// or PNG (PQ) or 32-bit float TIFF with [`ExportOptions::hdr`].
pub fn hdr_output(&self) -> bool {
self.hdr && matches!((self.format, self.bit_depth), (ExportFormat::Jpeg | ExportFormat::Avif, _) | (ExportFormat::Tiff, Some(32)))
self.hdr
&& matches!(
(self.format, self.bit_depth),
(ExportFormat::Jpeg | ExportFormat::Avif | ExportFormat::Png, _) | (ExportFormat::Tiff, Some(32))
)
}
/// The colour space the file is actually written in (AVIF: sRGB, or Rec. 2020 for HDR).
/// The colour space the file is actually written in (AVIF: sRGB, or Rec. 2020 for HDR; HDR
/// PNG: Rec. 2020).
pub fn effective_space(&self) -> OutputSpace {
match self.format {
ExportFormat::Avif if self.hdr => OutputSpace::Rec2020,
ExportFormat::Avif | ExportFormat::Png if self.hdr => OutputSpace::Rec2020,
ExportFormat::Avif => OutputSpace::Srgb,
_ => self.color_space,
}
@@ -1283,6 +1290,7 @@ pub fn encode_deep(img: &DeepImage, o: &ExportOptions, meta: Option<&Metadata>)
DeepSamples::F32(v) => EncodeImage::new(w, h, 3, Samples::F32(v)),
};
let r = match (o.format, &img.samples) {
(ExportFormat::Png, DeepSamples::F32(v)) if img.space == OutputSpace::Rec2020 => lightcraft_codecs::encode_png_pq(w, h, v, &meta),
(ExportFormat::Png, _) => encode::encode_png(&e, &meta),
(ExportFormat::Tiff, _) => encode::encode_tiff(&e, o.tiff_compression, &meta),
(ExportFormat::Avif, DeepSamples::F32(v)) if img.space == OutputSpace::Rec2020 => {