First of all, we have to find an image of the ghost or draw it freehand (as I did). Usually, we draw it at a rather high resolution. In this example we start from 118×118 pixels.
Note that when drawing the image, we should leave a black border on the left and right. The image thus drawn is, however, too large to be managed by 8-bit computers.
For this reason, we proceed to resize the image to a more suitable size, such as 16 pixels x 16 pixels. Note that we must impose “None” as a quality to avoid introducing additional nuances.
Once converted it is necessary to reduce the number of colors present in the image. This is necessary because the
img2tile program automatically detects the colors (as RGB) and assigns them to the 2-bit indices which, in fact, can only indicate 4 different colors.
Finally, before going back to processing the image, you need to convert it back to RGB in order to be free to assign precise colors.