These functions may include frame/format selection, resizing, cropping, alpha blending, compositing source images, rotating, color adjustment, and filtering.
[1] port/1188 The proliferation of mobile devices, screen resolutions, and pixel densities has forced web designers to create an ever-increasing number of image variations.
Declarative APIs (such as RIAPI) allow the client to describe resulting characteristics of the image, such as desired size, aspect ratio, rotation, fit modes, etc.
Imperative APIs, (such as IIP or IIIF) describe the operations to apply to the image in order, offering the user more control, but also more responsibility for calculations.
Responsive web design has driven the creation of dozens of new image servers which often integrate device or resolution detection.
Image servers may enable early adopters to begin using WebP before all browsers implement support.