| Value | Meaning |
|---|---|
| TJSAMP_4440 | 4:4:4 chrominance subsampling (no chrominance subsampling). The JPEG or YUV image will contain one chrominance component for every pixel in the source image. |
| TJSAMP_422 | 4:2:2 chrominance subsampling. The JPEG or YUV image will contain one chrominance component for every 2x1 block of pixels in the source image. |
| TJSAMP_420 | 4:2:0 chrominance subsampling. The JPEG or YUV image will contain one chrominance component for every 2x2 block of pixels in the source image. |
| TJSAMP_GRAY | Grayscale. The JPEG or YUV image will contain no chrominance components. |
| TJSAMP_440 | 4:4:0 chrominance subsampling. The JPEG or YUV image will contain one chrominance component for every 1x2 block of pixels in the source image. |
Chrominance subsampling options. When an image is converted from the RGB to the YUV colorspace as part of the JPEG compression process, some of the U and V (chrominance) components can be discarded or averaged together to produce a smaller image with little perceptible loss of image clarity (the human eye is more sensitive to small changes in brightness than small changes in color.) This is called "chrominance subsampling".