Photoshop was created in 1988 by Thomas and John Knoll. Since then, it has become the de facto industry standard in raster graphics editing, such that the terms "photoshopping" and "photoshop contest" were born. It can edit and compose raster images in multiple layers and supports masks, alpha compositing and several color models including RGB, CMYK, Lab color space (with capital L), spot color and duotone. Photoshop has vast support for graphic file formats but also uses its own PSD and PSB file formats which support all the aforementioned features. In addition to raster graphics, it has limited abilities to edit or render text, vector graphics (especially through clipping path), 3D graphics and video. Photoshop's featureset can be expanded by Photoshop plug-ins, programs developed and distributed independently of Photoshop that can run inside it and offer new or enhanced features.
- jpeg progressif
image is downloaded in lower resolution, displayed, then "progressively" downloaded and redisplayed until the full resolution is shown
- put multiple images (not photos) in one single png can highly optimize the weight of web images, the css will select the zone in the full image to display as single image, some tools like "compass" automatize this fonctionnality
- png 8 : to more optimized the png weight, png 8 options are available