Function decode_matcap_image_from_file 

pub fn decode_matcap_image_from_file(
    path: &Path,
) -> Result<(u32, u32, Vec<f32>), String>

Decode an image file from disk into float RGBA pixel data.

Returns (width, height, rgba_f32_pixels) where pixels are laid out as [r, g, b, a, r, g, b, a, ...] in linear float space.

Supports any format the image crate can open: HDR, JPEG, PNG, EXR, etc.