msx1 filter

The code still have some accuracy bugs when compaired with its sdlBasic version, since i were getting some problems when recoding it to Python-Gimp.
The script converts a rgb picture into msx1 (also colecovision and sega sg1000) display limitations, which have a predefined palette, and a maximum of 2 colours in each 8x1 pixels cell, trying to provide this cell as the most close as possible from their rgb original.
As well, the code is a bit slow (a 320x240 picture can take around 1 minute on a 2ghz dualcore computer) since it processes pixel by pixel.
I'm posting here the code anyway hoping i can fix it soon, or someone could help on it...