TK2048/graphics/conversion.txt

void convert_pic(uint16_t w, uint16_t h, const uint8_t *data, uint8_t *dest) {
	uint8_t remainder = 0;
	uint8_t remainder_size = 0;
	uint8_t pic_width_bytes = w / 8 + ((w % 8) ? 1 : 0);
	uint16_t spurious_bits = (pic_width_bytes * 8) - w;
	uint16_t counter = 0;
	
	
	for(uint16_t row = 0; row < h; row++) {
		remainder = 0;
		remainder_size = 0;
		
		// MSB is the color indicator
		for(uint8_t column = 0; column < pic_width_bytes; column++) {
			uint8_t pix_data = data[(pic_width_bytes * row) + column];
			uint8_t conv_data = (pix_data << remainder_size) | remainder;
			remainder_size++;
			remainder = (pix_data >> (8 - remainder_size)) & 0x7F;
			dest[counter++] = conv_data & 0x7F;
			
			if(remainder_size == 7) {
				dest[counter++] = remainder & 0x7F;
				remainder = 0;
				remainder_size = 0;
			}
		}
		
		if(remainder_size > spurious_bits) {
			uint8_t mask = ~((1 << remainder_size) - 1);
			dest[counter] = (dest[counter] & mask) | (remainder & 0x7F);
			counter++;
		}
	}
}