将 Bayer 编码 (RGGB) 和 16 位深度的 RAW 图像转换为 RGB：最终图像太暗并且偏绿 (Rust)

Question

I use a Rust library to parse raw ARW images (Sony Raw Format). I get a raw buffer of 16 bit pixels, it gives me the CFA (Color Filter Array) (which is RGGB), and the data buffer contains height * width pixels in bayer encoding. Each pixel is stored as 16 bit (however, I think the camera only uses 12 or 14 of the 16 bits for each pixel).

I'm using a Bayer library for the demosaicing process. Currently, my final image is too dark and has a greenish cast after the demosaic process. I guess the error is that before I pass the data to the bayer library, I try to transform each 16 bit value to 8 bit by dividing it by u16::max and multiplying it with u8::max . However, I don't know if this is the right approach.

I guess I need to perform additional steps between the parsing of the raw file and passing it to the bayer library. May I have any advice, please?

I can ensure that at least some demosaicing works. Here's a screenshot of the resulting image:

Current Code

The libraries I'm using are rawloader and bayer

let decoded_raw = rawloader::decode_file(path).unwrap();
let decoded_image_u16 = match &decoded_raw.data {
    RawImageData::Integer(data) => data,
    RawImageData::Float(_) => panic!("not supported yet"),
};

// u16 to u8 (this is probably wrong)
let mut decoded_image_u8 = decoded_image_u16
    .iter()
    .map(|val| {
        // todo find out how to interpret the u16!
        let val_f32 = *val as f32;
        let u16_max_f32 = u16::MAX as f32;
        let u8_max_f32 = u8::MAX as f32;
        (val_f32 / u16_max_f32 * u8_max_f32) as u8
    })
    .collect::<Vec<u8>>();

// prepare final RGB buffer
let bytes_per_pixel = 3; // RGB
let mut demosaic_buf = vec![0; bytes_per_pixel * decoded_raw.width * decoded_raw.height];
let mut dst = bayer::RasterMut::new(
    decoded_raw.width,
    decoded_raw.height,
    bayer::RasterDepth::Depth8,
    &mut demosaic_buf,
);

// DEMOSAIC
// adapter so that `bayer::run_demosaic` can read from the Vec
let mut decoded_image_u8 = ReadableByteSlice::new(decoded_image_u8.as_slice());

bayer::run_demosaic(
    &mut decoded_image_u8,
    bayer::BayerDepth::Depth8,
    // RGGB is definitely right for my AWR file
    bayer::CFA::RGGB,
    bayer::Demosaic::Linear,
    &mut dst,
)
.unwrap();

Answer 1

I'm not sure if this is connected to the actual problem, but your conversion is way overkill.

To convert from the full range of a u16 to the full range of a u8 , use:

(x >> 8) as u8

fn main() {
    let convert = |x: u16| (x >> 8) as u8;

    println!("{} -> {}", 0, convert(0));
    println!("{} -> {}", 30000, convert(30000));
    println!("{} -> {}", u16::MAX, convert(u16::MAX));
}

0 -> 0
30000 -> 117
65535 -> 255

I might be able to help you further if you post the input image, but without being able to reproduce your problem I don't think there will be much else here.