How to use the command pnmquant (with examples)

The pnmquant command is a useful tool for quantizing the colors in a PNM image into a smaller set. It combines the functionalities of pnmcolormap and pnmremap and accepts the union of their options, except for -mapfile option. With pnmquant, you can generate an image using only a specified number of colors or less, while keeping the output as close as possible to the input image.

Use case 1: Generate an image using a specified number of colors

Code:

pnmquant n_colors path/to/input.pnm > path/to/output.pnm

Motivation: Sometimes, you may need to reduce the number of colors in an image to optimize its size or to achieve a specific aesthetic. By using pnmquant, you can generate a new image that has only a specified number of colors, making it more efficient and visually appealing.

Explanation:

• n_colors: This argument specifies the maximum number of colors to be used in the output image. The command will try to find the best approximation of the input image using the given number of colors.
• path/to/input.pnm: This is the path to the input PNM image file that you want to convert.
• path/to/output.pnm: This is the path where you want to save the resulting image.

Example output: Suppose you have an input image with 256 colors and you want to generate a new image with only 16 colors. Running the following command will quantize the colors in the input image:

pnmquant 16 input.pnm > output.pnm