Convert GIFs to black and white using gifsicle (2023-07-29)
If you need to convert a GIF image from color or grey scale into just black and white, here is a recipe using a command line tool called gifsicle
Here is my original image (captured from the Playdate Simulator).
And after running this command:
gifsicle --gamma=1 --use-colormap=bw < rain.gif > rain_bw.gif
We get a black and white image. I needed to use the gamma flag for this image, since it's so low contrast, the default result was a solid black image.
And... that's pretty much it. For more details on various options for
gifsicle, see the gifsicle docs
To go the other direction, we need a custom color map in the gifsicle format. Here is an example of one in the Playdate Simulator color scheme:
50 47 40 177 174 167
And then pass that into the
gifsicle --gamma=1 --use-colormap=pd_colors.txt <rain_bw.gif > rain_pd.gif