ppmwheel

Generate a color wheel of type Ppmcirc

$ ppmwheel [diameter] > [path/to/output.ppm]

$ ppmwheel [[-huev|-huevalue]] [diameter] > [path/to/output.ppm]

$ ppmwheel [[-hues|-huesaturation]] [diameter] > [path/to/output.ppm]

ppmwheel [width] [height]

ppmwheel is a utility from the Netpbm package designed to create a PPM (Portable Pixmap) image representing a standard color wheel.

The generated image displays a circular gradient. The center of the circle is white, and colors radiate outwards, representing increasing saturation. Simultaneously, colors vary circumferentially around the circle, representing a full range of hues. The circumference of the circle shows fully saturated hues.

It is commonly used for testing display devices, color printers, or simply for visual demonstration of color spaces. By default, it generates a 200x200 pixel image, but custom dimensions can be specified.

The command does not support any command-line options or flags for modifying its behavior beyond specifying image dimensions. It outputs directly to standard output, typically requiring redirection to a file. The output format is always PPM.

The width and height values are optional positional arguments that define the output image's dimensions in pixels. If omitted, ppmwheel defaults to generating a 200x200 pixel image.

For example, to create a 400x300 color wheel image, you would use: ppmwheel 400 300 > wheel.ppm

The output of ppmwheel is a PPM (Portable Pixmap) image, which is a plain text or binary format that can be viewed or converted using other Netpbm tools or image viewers that support the format. The output is sent to standard output (stdout) and typically needs to be redirected to a file.

ppmwheel was originally authored by Jef Poskanzer and first copyrighted in 1989. It is a foundational utility within the Netpbm toolkit, which has been instrumental in image processing on Unix-like systems since its inception.

ppm(5), netpbm(1)