Function read_coefficients 

pub fn read_coefficients(jpeg: &[u8]) -> Result<JpegCoefficients, DctError>

Decode the quantized DCT coefficients from a baseline JPEG.

Returns JpegCoefficients containing all blocks for all components. Does not dequantize or apply IDCT; values are the raw quantized integers.

Errors

Returns DctError if the input is not a supported baseline JPEG, if required markers are missing, or if the entropy stream is corrupt.