Chroma subsampling is the practice of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance.
In full size, this image shows the difference between four subsampling schemes. Note how similar the color images appear. The lower row shows the resolution of the color information.
JPEG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality. Since its introduction in 1992, JPEG has been the most widely used image compression standard in the world, and the most widely used digital image format, with several billion JPEG images produced every day as of 2015.
The compressed 8×8 squares are visible in the scaled-up picture, together with other visual artifacts of the lossy compression.
Visual impact of a jpeg compression on Photoshop on a picture of 4480x4480 pixels
Image: JPEG example image
Image: JPEG example image decompressed
