ppmtopbm

ppmtopbm [ppmfile]

ppmfile
    The input PPM file. If not specified, ppmtopbm reads from standard input.

The ppmtopbm command in Linux converts a Portable Pixmap (PPM) image file into a Portable Bitmap (PBM) image file.

PPM is a relatively simple image format that stores color information as RGB values, while PBM is a black and white (binary) image format. As such, ppmtopbm essentially performs a thresholding operation, where each pixel in the PPM image is converted to either black or white based on its luminance.

The command reads a PPM image from standard input or a specified file and writes the resulting PBM image to standard output. This command is primarily used for converting color images to black and white for applications or devices that only support binary images. The output can then be used by other tools or programs that require a PBM file as input.

By default, the threshold for converting color values to black and white is set to the midpoint of the brightness range; however, this can't be controlled by the end user.

ppmtopbm converts a color image (PPM) to a black-and-white image (PBM). Since information is lost during the conversion, the PBM format takes less space than PPM format.

If an input file is not explicitly specified, ppmtopbm will read image data from standard input. The resulting PBM image will be written to standard output.

pbmtopgm(1), pbmtoppm(1), ppmtoy4m(1), ppmtojpeg(1)