Chrome's Clever JPEG Decoding Trick Makes Tiny Images Look Different
Why Tiny JPEGs Look Different in Chrome
A developer noticed a logo rendered slightly thicker in Chrome than in Firefox. The culprit isn't a bug but a performance optimization: when scaling JPEGs down, Chrome uses partial IDCT scaling via libjpeg-turbo, decoding only low-frequency data. This skips high-frequency details that would be lost anyway, saving memory and time, but can alter the appearance of small images. The article explains how JPEG's frequency-domain encoding makes this possible and advises against using JPEG for icons.
Because it was rendered so small, it was decoded at one-eighth scale using partial IDCT scaling, so the only data from the frequency representation that remained was the constant component; all the edge softening and gradients were not used.