But, next comes a quantification algorithm that rounds the frequency values within the 8x8 squares. If this is done with high accuracy, often one doesn't even notice it within the picture. But, increasing quantification also results in higher data compression, which also results in more data loss, which creates ... artifacts. You can see the typical jpeg raster effect, whenever using high jpeg compression.Here's a cool animation of an image being jpeg compressed 600 times (in a 20 second short movie). The simple algorithm goes:
Open the last saved jpeg image
Save it as a new jpeg image with slightly more compression
Repeat 600 times.
Generation Loss from hadto on Vimeo.