For bigger images, the pixel index might not fit in a int16. Therefore,
int is needed during the calculation.
While fixing this bug, I've added a few tests that verify the Image
implementation by creating images, filling them with random data, and
then checking whether they still contain the same data. This test failed
before the patch.
This has been optimized for working with SPI displays like the ST7789.
By working directly in the native color format of the display, graphics
operations can be much, _much_ faster.
Also, this makes it easier to use a different color format like RGB444
simply by changing the generic type.
deadprogram
Daniel Esteban
Ayke van Laethem