There are a whole bunch of apps in the mobile world that “improve” the perceptual quality of images. One recent one automagically enhances most of the issues found in pictures taken on mobile apps. They exclaim the virtues of enhancement of images through “colour recovery”, exposure compensation, dehazing, foliage enhancement, tint perfection. Sometimes the apps are almost advertised as being some sort of magic panacea for fixing photographs. There of course is no such thing. Consider the example below. The photograph on the left (of a fire hydrant in Reykjavik), is somewhat dull (I can’t remember why, but chances are those were the actual colours). The photograph on the right has been “enhanced” by improving the vibrancy of the colour in the image. Some might call this “colour recovery”, but that seems unrealistic if the colours were faded to begin with. But let’s looks beyond that – what does this enhancement involve?
Basically this just involves saturating the colour, and the easiest way of doing this is to convert the image from RGB to HSB (Hue-Saturation-Brightness) colour space, and multiply all the pixels in the Saturation layer by 1.4. This increases the purity of colour, making it appear more vivid. The HSB is then converted back to RGB. Nice result, but the original colours probably represent better what the scene actually looking like.
Some photos don’t really need much enhancing, and of course it helps if you take good photos to begin with.