@SlimShady Downsampling an image is a compression strategy, but it is often a bad one. Consider a case where you have a black image with a small, high-resolution checkboard pattern in the center. Downsampling that image would be a bad compression strategy, because the high-frequency information associated with the checkerboard pattern would be lost. A better compression algorithm might preserve this high-frequency information, while still lowering the size of the overall image.
How is compression different from downsampling?
@SlimShady Downsampling an image is a compression strategy, but it is often a bad one. Consider a case where you have a black image with a small, high-resolution checkboard pattern in the center. Downsampling that image would be a bad compression strategy, because the high-frequency information associated with the checkerboard pattern would be lost. A better compression algorithm might preserve this high-frequency information, while still lowering the size of the overall image.