Take any photograph in Photoshop. First, save one copy of it as a compressed JPG.
Now, on the original, add a small densely repeating tiled pattern multiplied on top as a layer. Like a halftone effect, dot texture, whatever. Technically you're adding more order and less chaos. The resulting image won't compress as efficiently.
Take any photograph in Photoshop. First, save one copy of it as a compressed JPG.
Now, on the original, add a small densely repeating tiled pattern multiplied on top as a layer. Like a halftone effect, dot texture, whatever. Technically you're adding more order and less chaos. The resulting image won't compress as efficiently.