[spiralpolitik]

On MacOS/iOS the ImageIO framework handles encoding and decoding images. Adding support for your image format to that framework means everything else just works once the image is decoded.

Another framework, CoreImage, provides generic operations to filter and transform images decoded by ImageIO. This provides hardware acceleration and other good stuff that make things like CSS transforms super fast and efficient.

While it can be done in JavaScript it would be much much slower, less efficient, and kill your battery.