How to set the DPI of an image before saving it?

[xYx-c]

pub fn build_dpi_chunk(dpi: u32) -> Vec<u8> {
    let dpm = 39.370_08 * dpi as f32;
    let rounded_dpm = dpm.round() as u32;

    let mut data = Vec::new();
    data.extend_from_slice(&rounded_dpm.to_be_bytes());
    data.extend_from_slice(&rounded_dpm.to_be_bytes());

    data.push(1);
    data
}

pub fn png_with_dpi<P>(imgbuf: ImageBuffer<P, Vec<u8>>, dpi: u32) -> Result<ImageBuffer<P, Vec<u8>>, std::io::Error>
where
    P: Pixel<Subpixel = u8>,
{
    let (width, height) = imgbuf.dimensions();
    let mut encoder = png::Encoder::new(imgbuf.clone().into_raw(), width, height);

    match <P as Pixel>::CHANNEL_COUNT {
        4 => encoder.set_color(png::ColorType::Rgba),
        3 => encoder.set_color(png::ColorType::Rgb),
        _ => {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                "Incorrect color channel count / format.",
            ))
        },
    }
    encoder.set_depth(png::BitDepth::Eight);
    encoder.set_compression(png::Compression::Best);
    let data = build_dpi_chunk(dpi);

    let mut writer = encoder.write_header()?;

    writer.write_chunk(png::chunk::pHYs, data.as_slice())?;
    writer.write_image_data(&imgbuf)?;


    Ok(imgbuf)
}

I have tried using like this but it doesn't work correctly.

[fintelia]

Duplicate of image-rs/image-png#482