This Photoshop plugin, the 12bits Filter, reduces the color depth of an image's channels to 4 bits or 16 values for each one.
The 12bits Filter can be used as a great demonstration or template of a straightforward, cross-platform filter. Essentially, this filter quantizes each image channel into 16 values, which involves taking the four most substantial bits of each pixel value and multiplying it by 17 so that the range continues to be between 0-255. This process results in the output values being anywhere from 0*17 to 15*17 with a maximum of 4096 colors for a full-color RGB image.
In conclusion, if you are looking for a simple and effective way to reduce the color depth of an image, the 12bits Filter Photoshop plugin is an excellent option to consider.
Version 1.3f1: N/A