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Decode HEIC with correct color space #731

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Decode HEIC with correct color space #731

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1cafbd3
Decode HEIC with correct color space
joshuamegnauth54 Aug 10, 2025
9fe569d
Merge branch 'master' into heic-use-correct-chroma-space
Stoppedpuma Sep 12, 2025
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14 changes: 12 additions & 2 deletions Cargo.lock
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3 changes: 2 additions & 1 deletion Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -122,6 +122,7 @@ arboard = { version = "3.4", features = ["wayland-data-control"] }
clap = "3.2" # DO NOT UPDATE unless you test extensively on mac. This will break the mac app.
dirs = "6.0"
env_logger = "0.11"
yuv = { version = "0.8", optional = true }

[features]
default = [
Expand All @@ -132,7 +133,7 @@ default = [
"j2k",
"jxlcms",
]
heif = ["libheif-rs"]
heif = ["libheif-rs", "yuv"]
avif_native = ["avif-decode"]
dav1d = ["libavif-image"]
file_open = ["rfd"]
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140 changes: 112 additions & 28 deletions src/image_loader.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -159,7 +159,7 @@ pub fn open_image(
#[cfg(feature = "heif")]
"heif" | "heic" => {
// Built on work in https://github.com/rsuu/rmg - thanks!
use libheif_rs::{ColorSpace, HeifContext, LibHeif, RgbChroma};
use libheif_rs::{Chroma, ColorSpace, HeifContext, LibHeif, RgbChroma};

let lib_heif = LibHeif::new();
let mut ctx = HeifContext::read_from_file(&img_location.to_string_lossy().to_string())?;
Expand All @@ -173,34 +173,118 @@ pub fn open_image(
ctx.set_security_limits(&limits)?;
}
let handle = ctx.primary_image_handle()?;
let img = lib_heif.decode(&handle, ColorSpace::Rgb(RgbChroma::Rgba), None)?;
let planes = img.planes();
let interleaved = planes
.interleaved
.context("Can't create interleaved plane")?;

let data = interleaved.data;
let width = interleaved.width;
let height = interleaved.height;
let stride = interleaved.stride;

let mut res: Vec<u8> = Vec::new();
for y in 0..height {
let mut step = y as usize * stride;

for _ in 0..width {
res.extend_from_slice(&[
data[step],
data[step + 1],
data[step + 2],
data[step + 3],
]);
step += 4;
let img = lib_heif.decode(&handle, ColorSpace::Undefined, None)?;

let i = match img.color_space() {
Some(ColorSpace::Rgb(chroma @ (RgbChroma::Rgb | RgbChroma::Rgba))) => {
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libheif can use 10 and 12 bits as well, not only 8 bit images.

let planes = img.planes();
let interleaved = planes
.interleaved
.context("Can't create interleaved plane")?;

let data = interleaved.data;
let width = interleaved.width;
let height = interleaved.height;

match chroma {
RgbChroma::Rgb => DynamicImage::ImageRgb8(
image::RgbImage::from_vec(width, height, data.to_vec())
.context("Failed creating RGB image from HEIC")?,
),
RgbChroma::Rgba => DynamicImage::ImageRgba8(
image::RgbaImage::from_vec(width, height, data.to_vec())
.context("Failed creating RGBA image from HEIC")?,
),
_ => unreachable!("Guarded by Rgb | Rgba"),
}
}
}
let buf = image::ImageBuffer::from_vec(width as u32, height as u32, res)
.context("Can't create HEIC/HEIF ImageBuffer with given res")?;
let i = DynamicImage::ImageRgba8(buf);
Some(ColorSpace::YCbCr(chroma)) => {
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I'm not sure if this branch is correct one.

It's missing:

  • Checking the image bit depth, and handling or rejecting unsupported depths. Typically, libheif supports 8-bit and 10-bit for HEIC.
  • Accounting that YUV range is subject to change.
  • Accounting for the YUV matrix, which may vary. For HEIC, it is usually BT.709 rather than BT.601. But it's needed to be queried from libheif.

let planes = img.planes();
let y = planes.y.context("YUV is missing Y")?;
let y_plane = y.data;
let y_stride = y.stride.try_into()?;
let u = planes.cb.context("YUV is missing U")?;
let u_plane = u.data;
let u_stride = u.stride.try_into()?;
let v = planes.cr.context("YUV is missing V")?;
let v_plane = v.data;
let v_stride = v.stride.try_into()?;
let width = img.width();
let height = img.height();
let planar_image = yuv::YuvPlanarImage {
y_plane,
y_stride,
u_plane,
u_stride,
v_plane,
v_stride,
width,
height,
};

let rgba_stride = width * 4;
let len = (rgba_stride * height) as usize + (width * 4) as usize;
let mut rgba = vec![0u8; len];
let range = yuv::YuvRange::Limited;
let matrix = yuv::YuvStandardMatrix::Bt601;

match chroma {
Chroma::C420 => yuv::yuv420_to_rgba(
&planar_image,
&mut *rgba,
rgba_stride,
range,
matrix,
),
Chroma::C422 => yuv::yuv422_to_rgba(
&planar_image,
&mut *rgba,
rgba_stride,
range,
matrix,
),
Chroma::C444 => yuv::yuv444_to_rgba(
&planar_image,
&mut *rgba,
rgba_stride,
range,
matrix,
),
}?;
DynamicImage::ImageRgba8(
image::RgbaImage::from_vec(width, height, rgba)
.context("RGBA8 image from HEIC")?,
)
}
Some(ColorSpace::Monochrome) => {
let planes = img.planes();
let y = planes.y.context("Grayscale image is missing luma")?;
let buf = y.data.to_vec();
let width = img.width();
let height = img.height();

let i = DynamicImage::ImageLuma8(
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Monochrome used in HEIC is YUV image with only Y plane, so it's required to handle YUV range and YUV matrix as well and image also could be 10 bit.

GrayImage::from_vec(width, height, buf)
.context("Grayscale image from HEIC")?,
)
.into_rgb8();
DynamicImage::ImageRgb8(i)
}
_ => {
let planes = img.planes();
let buf = planes
.interleaved
.context("HEIC image is missing data")?
.data
.to_vec();
let width = img.width();
let height = img.height();
DynamicImage::ImageRgba8(
image::RgbaImage::from_vec(width, height, buf)
.context("Unknown image from HEIC")?,
)
}
};

_ = sender.send(Frame::new_still(i));
return Ok(receiver);
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