The height of the cropping region. Setting this to 0 is the equivalent of setting it to the height of the source JPEG image - y.
The width of the cropping region. Setting this to 0 is the equivalent of setting it to the width of the source JPEG image - x.
The left boundary of the cropping region. This must be evenly divisible by the MCU block width (see #tjMCUWidth.)
The upper boundary of the cropping region. This must be evenly divisible by the MCU block height (see #tjMCUHeight.)
Cropping region