bitmaps are sometimes inverted

[AberDerBart]

I tried rendering bitmaps, but in some cases the result was inverted.
Here is an example containing the source monochrome bitmap and the generated header file: example.zip

[daschr]

Currently, the library will draw all black pixels (see https://github.com/daschr/pico-ssd1306/blob/main/example/test.bmp).
Your keyboard example uses black as the background color and white as the foreground.
You may negate the bmp before embedding it (f.e using imagemagick and convert keyboard_24_16.bmp -negate keyboard_24_16_negated.bmp).

One could also add an option to draw the image negative.

[AberDerBart]

There is code in the bin2c tool that handles foreground and backgroud colors but somehow it does not work for my image, so I guess that is a bug in bin2c