NxWidgets/tools README File
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bitmap_converter.py
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This script converts from any image type supported by Python imaging library to
the RLE-encoded format used by NxWidgets.
RLE (Run Length Length) is a very simply encoding that compress quite well
with certain kinds of images: Images that that have many pixels of the
same color adjacent on a row (like simple graphics). It does not work well
with photographic images.
But even simple graphics may not encode compactly if, for example, they have
been resized. Resizing an image can create hundreds of unique colors that
may differ by only a bit or two in the RGB representation. This "color
smear" is the result of pixel interpolation (and might be eliminated if
your graphics software supports resizing via pixel replication instead of
interpolation).
When a simple graphics image does not encode well, the symptom is that
the resulting RLE data structures are quite large. The pallette structure,
in particular, may have hundreds of colors in it. There is a way to fix
the graphic image in this case. Here is what I do (in fact, I do this
on all images prior to conversion just to be certain):
- Open the original image in GIMP.
- Select the option to select the number of colors in the image.
- Pick the smallest number of colors that will represent the image
faithfully. For most simple graphic images this might be as few as 6
or 8 colors.
- Save the image as PNG or other lossless format (NOT jpeg).
- Then generate the image.
