Failing to convert HEIC to JPEG

[vincent-herlemont]

I am trying to convert a HEIC file to JPEG using the library. Here is my test:

#[test]
fn convert_to_jpg() -> Result<()> {
    let read_ctx = HeifContext::read_from_file("./data/IMG_0832.HEIC")?;
    let handle = read_ctx.primary_image_handle()?;

    let lib_heif = LibHeif::new();
    let image = lib_heif.decode(&handle, ColorSpace::Rgb(RgbChroma::Rgb), None)?;

    let mut write_context = HeifContext::new()?;
    let mut encoder = lib_heif.encoder_for_format(CompressionFormat::Jpeg)?;
    encoder.set_quality(EncoderQuality::LossLess)?;
    let encoding_options = EncodingOptions::new().unwrap();
    write_context.encode_image(&image, &mut encoder, Some(encoding_options))?;

    let buf = write_context.write_to_bytes()?;

    let mut file = File::create("./data/IMG_0832.jpg").unwrap();
    file.write_all(&buf).unwrap();

    Ok(())
}

Here is the error I encountered:

Error: HeifError { code: EncodingError, sub_code: EncoderEncoding, message: "Error during encoding or writing output file: Encoding problem: JPEG encoding error" }

By adding logs in the C++ binder library, I discovered that the logs stop at this line jpeg_create_compress(&cinfo); encoder_jpeg.cc#L369, then the error is returned here encoder_jpeg.cc#L354.

I might be configuring the encoder incorrectly. Do you have any suggestions for solutions or investigations?

---

Note that the same image converts very well with similar code using Av1 by utilizing CompressionFormat::Av1.

[Cykooz]

I think it will be more easy if you use image crate to encode and save an image as JPEG-file. Or do you need a heif container with a JPEG-encoded image inside? libheif doesn't create JPEG-files. It creates HEIF-files with somehow encoded images inside.

[vincent-herlemont]

I think it will be more easy if you use image crate to encode and save an image as JPEG-file.

Hmm, I do understand that if it is possible to do that, it would be better.

But once I have retrieved Image after calling the decode function, how do I put the data into the image crate?

[Cykooz]

You can get &[u8] buffer with pixels data from corresponding plane(s). For ColorSpace::Rgb(RgbChroma::Rgb) it is interleaved plane:

let planes = image.planes();
let interleaved_plane = planes.interleaved.unwrap();
assert_eq!(interleaved_plane.width, 1024);
assert_eq!(interleaved_plane.height, 800);
assert_eq!(interleaved_plane.stride, 0);
let buffer: &[u8] = interleaved_plane.data;

In simple case (stride == 0) DynamicImage is created easy:

let rgb_image = image::RgbImage::from_raw(
    interleaved_plane.width, 
    interleaved_plane.height, 
    buffer.to_vec(),
).unwrap();
let dyn_image = image::DynamicImage::ImageRgb8(rgb_image);

I'm not sure if the image crate supports images with stride > width * pixel_size. So in that case you have to copy image rows one by one (without extra bytes at the end of each) from buffer to Vec<u8>.

[vincent-herlemont]

Thank you for your suggestions! It works perfectly (I adapted width, height, stride) to the image I have locally.

Here is the final code:

#[test]
fn convert_to_jpg_with_image_crate() -> Result<()> {
    let read_ctx = HeifContext::read_from_file("./data/IMG_0832.HEIC")?;
    let handle = read_ctx.primary_image_handle()?;

    let lib_heif = LibHeif::new();
    let image = lib_heif.decode(&handle, ColorSpace::Rgb(RgbChroma::Rgb), None)?;
    let planes = image.planes();
    let interleaved_plane = planes.interleaved.unwrap();
    assert_eq!(interleaved_plane.width, 4032);
    assert_eq!(interleaved_plane.height, 3024);
    assert_eq!(interleaved_plane.stride, 12096);

    let buffer: &[u8] = interleaved_plane.data;
    let rgb_image = image::RgbImage::from_raw(
        interleaved_plane.width, 
        interleaved_plane.height, 
        buffer.to_vec(),
    ).unwrap();
    let dyn_image = image::DynamicImage::ImageRgb8(rgb_image);  

    let mut file = File::create("./data/IMG_0832.jpg").unwrap();
    dyn_image.write_to(&mut file, image::ImageFormat::Jpeg).unwrap();

    Ok(())
}

I'm not sure if the image crate supports images with stride > 0. So in that case you have to copy image rows one by one (without extra bytes at the end of each) from buffer to Vec<u8>.

I feel like the image library does not take stride into account; the image result does not seem to be affected.