2013-05-12 15:47:16 +02:00
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NxWidgets/tools README File
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===========================
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bitmap_converter.py
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-------------------
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This script converts from any image type supported by Python imaging library to
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the RLE-encoded format used by NxWidgets.
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RLE (Run Length Length) is a very simply encoding that compress quite well
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with certain kinds of images: Images that that have many pixels of the
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same color adjacent on a row (like simple graphics). It does not work well
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with photographic images.
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But even simple graphics may not encode compactly if, for example, they have
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been resized. Resizing an image can create hundreds of unique colors that
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may differ by only a bit or two in the RGB representation. This "color
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smear" is the result of pixel interpolation (and might be eliminated if
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your graphics software supports resizing via pixel replication instead of
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interpolation).
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When a simple graphics image does not encode well, the symptom is that
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the resulting RLE data structures are quite large. The pallette structure,
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in particular, may have hundreds of colors in it. There is a way to fix
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the graphic image in this case. Here is what I do (in fact, I do this
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on all images prior to conversion just to be certain):
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- Open the original image in GIMP.
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- Select the option to select the number of colors in the image.
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- Pick the smallest number of colors that will represent the image
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faithfully. For most simple graphic images this might be as few as 6
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or 8 colors.
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- Save the image as PNG or other lossless format (NOT jpeg).
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- Then generate the image.
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