pgmtopgm

Copy PGM file from stdin to stderr

$ pgmtopgm

$ pgmtopgm -version

pgmtopgm [pgmfile]

-help
    Displays a help message about the command and its common Netpbm options.

-version
    Outputs the Netpbm version information.

pgmtopgm is a utility from the Netpbm toolkit, designed to read a Portable Graymap (PGM) image from its standard input (or a specified file) and write the identical PGM image to its standard output.

Its primary purpose is not to perform any image transformation, but rather to serve as a template or example program for developers. It demonstrates the fundamental structure and input/output handling common to Netpbm image filters. Programmers wishing to write new PGM-processing tools can use pgmtopgm's source code as a starting point.

While it performs no actual image manipulation, it can still be useful in scripting pipelines as a no-operation (no-op) filter, for example, to verify the validity of a PGM stream or to explicitly mark a stage in a complex image processing pipeline. It faithfully preserves the PGM format, including header and pixel data, without any alteration.

As a template program, pgmtopgm performs no actual image processing or modification. Its utility is primarily for development or as a no-operation filter; it does not introduce any image quality changes.

The source code of pgmtopgm is intentionally simple and serves as an excellent starting point for programmers wishing to develop new Netpbm utilities that process PGM images. It illustrates how to correctly handle PGM file headers, pixel data, and error conditions within the Netpbm framework, ensuring compatibility and adherence to Netpbm conventions.

Because pgmtopgm reads from standard input and writes to standard output, it integrates seamlessly into shell pipelines. Although it doesn't modify the image, it can be used as a placeholder or a 'no-op' filter to explicitly pass a PGM image through a stage, or to test pipeline integrity without altering data, ensuring the PGM stream remains valid throughout the process.

Part of the long-standing Netpbm image processing suite, pgmtopgm was conceived not as a functional tool but as a foundational example. Its existence reflects the modular design philosophy of Netpbm, providing a clear and minimal blueprint for developers to extend the toolkit's capabilities by writing new PGM filters. It has been a standard component of the Netpbm distribution for many years, serving its role as a developer's utility.

netpbm(1), pgm(5), anytopgm(1), pbmtopgm(1), ppmtopgm(1), pgmtoppm(1)