rgb3toppm
Combine three PGM images into one PPM image. tldr-pages
On several platforms
Several platforms
Combine three PGM images (representing red, green, and blue color components) into one PPM image
rgb3toppm path/to/red_file.ppm path/to/green_file.ppm path/to/blue_file.ppm >path/to/output.ppmIdentify