Encoding The Pixels
After the header the image itself starts. This example will use the following 72x28 pixel image.
The first 8 pixels, reading right from the top left hand corner are one white (0) followed by seven blacks (1111111), giving the first byte, in Binary, as 01111111.
Converting from the binary 01111111 to hex, results in the first byte that represents the pixels (7F). The next 8 characters are 8 blacks (11111111 or FF) and so on.
When all pixels from the top row are encoded, simply move to the next. There are no markers to indicate a new row, that information is contained in the header.
In the case of an OTA bitmap that is not a multiple of eight pixels in width, a single byte is used to convey information from two lines (e.g. two pixels from the first row and six from the second.) This is not the case in some other formats, so it is important to exercise care when converting between OTA and formats like WBMP.
Read more about this topic: OTA Bitmap