Image enhancements

[malyvsen]

ImageToPrintCommands now accepts an array of IEnhancer - image filters to apply before dithering. I implemented two enhancers:

• HDREnhancer - adjusts local brightness to avoid bright areas becoming entirely white (and vice versa for dark ones)
• ContrastEnhancer - does what it says on the tin :)
• QuantileEnhancer - makes sure that the the distribution of brightness levels is uniform across the image

I'd go for calling ImageToPrintCommands with enhancers = {new QuantileEnhancer(0.5f), new HDREnhancer(0.1f, 8), new ContrastEnhancer(0.25f, 16)}.

Also! I didn't test this on the device, just made sure that pictures look nice after some enhancements and dithering.

[malyvsen]

Using only ContrastEnhancer seems to work better for screenshots (which do have large white areas which we don't want to gray out). Adding QuantileEnhancer with a positive arguments helps screenshots even more.

[fonsp]

OH NO i didn't see this until now 💔