Convert to greyscale

[Hengjie]

One common application for sites is to use photon for responsive images (e.g. images loaded on iPhone are smaller in dimension and file size than that of a desktop monitor). Typically, you'd want to load a low resolution image first to act as a placeholder and have it replaced with the right resolution image later.

Is it possible to use photon to generate a low resolution image that's greyscale? The benefit is that it'd be a smaller file to load (compared to color images) and provide an feel that the site is fast to load.