34 lines
1.5 KiB
ReStructuredText
34 lines
1.5 KiB
ReStructuredText
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===============
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Host Side Tools
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===============
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NxWidgets ``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 Encoding) 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 same
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color adjacent on a row (like simple graphics). It does not work well with
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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 may
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differ by only a bit or two in the RGB representation. This "color smear" is the
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result of pixel interpolation (and might be eliminated if your graphics software
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supports resizing via pixel replication instead of interpolation).
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When a simple graphics image does not encode well, the symptom is that the
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resulting RLE data structures are quite large. The palette structure, in
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particular, may have hundreds of colors in it. There is a way to fix the graphic
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image in this case. Here is what I do (in fact, I do this on all images prior to
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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 faithfully.
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For most simple graphic images this might be as few as 6 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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