ppmrainbow

Generate multi-color gradient images

TLDR

Generate rainbow gradient

$ ppmrainbow -width [100] -height [50] [color1] [color2] > [output.ppm]

Create red to blue gradient

$ ppmrainbow -width 200 -height 100 red blue > [gradient.ppm]

Multiple color gradient

$ ppmrainbow -width 300 -height 50 red yellow green blue > [rainbow.ppm]

ppmrainbow creates a horizontal color gradient image that smoothly transitions through the specified color stops. Any number of named colors can be provided, and the tool interpolates between them evenly across the image width.This is useful for creating gradient backgrounds, color bars for testing, or decorative elements. The -norepeat option prevents the gradient from wrapping back to the first color. Part of the Netpbm toolkit.