31 lines
1.4 KiB
Markdown
31 lines
1.4 KiB
Markdown
# Tools
|
|
|
|
## NxWidgets `bitmap_converter.py`
|
|
|
|
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 palette 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.
|