anytopnm

Convert an input image to PBM, PGM, or PPM format irrespective of the input type

$ anytopnm [path/to/input] > [path/to/output.pnm]

$ anytopnm [[-v|-version]]

anytopnm [options] [input_file]

input_file
    The path to the input image file. If omitted, anytopnm reads image data from standard input (stdin). The file format will be automatically detected.

options
    Any options specified on the command line are not processed by anytopnm itself, but are passed directly to the specific image converter program (e.g., jpegtopnm, pngtopnm) that anytopnm automatically selects based on the input file format. Refer to the manual pages of individual *to*pnm converters for their specific options.

anytopnm is a powerful front-end utility from the Netpbm package designed to convert various image formats into the standard Netpbm (Portable Anymap) format. It acts as a universal adapter, automatically detecting the input file's format (e.g., JPEG, PNG, GIF, TIFF, XBM) and piping it through the appropriate specific Netpbm converter (like jpegtopnm, pngtopnm, giftoppm, etc.).

This automatic detection makes anytopnm incredibly convenient when you are unsure of the input image's exact format or when dealing with a mix of formats. It reads the input image either from a specified file or from standard input, and always writes the resulting PNM (Portable Pixmap, Greymap, or Bitmap) data to standard output. While anytopnm itself has no command-line options, it intelligently passes any options you provide to the underlying specific converter, allowing for flexible control over the conversion process.

Format Detection: anytopnm relies on 'magic numbers' within the file content or on the filename extension to identify the format. If detection fails, it may default to interpreting the input as a Netpbm image, which can lead to errors for other formats.

Limited Support: It only supports formats for which a corresponding *to*pnm converter is installed and available in the system's PATH. It does not recognize every possible image format.

Output Fixed to PNM: The output format is always PNM (PBM, PGM, or PPM). It cannot convert to other non-Netpbm formats directly.

Error Handling: Error messages can sometimes be cryptic as they may originate from the underlying converter.

anytopnm operates by first attempting to identify the input image's format. It does this by checking a 'magic number' (a unique byte sequence) at the beginning of the file, or by examining the filename extension. Once the format is identified, it dynamically constructs a command, typically piping the input file through the appropriate specialized Netpbm converter (e.g., cat image.jpg | jpegtopnm) and then sends the PNM output to standard output. This mechanism allows anytopnm to efficiently handle various formats without needing to implement all conversion logic itself.

Regardless of the input image format, anytopnm always produces output in one of the Netpbm formats: Portable Pixmap (PPM for color images), Portable Greymap (PGM for grayscale images), or Portable Bitmap (PBM for black and white images). The specific PNM variant depends on the color depth and content of the input image. These PNM formats are simple, uncompressed, and widely used as an intermediate format within the Netpbm suite for further processing with other tools.

anytopnm is a core component of the Netpbm project, a venerable suite of graphics utilities dating back to the late 1980s. Its development arose from the need to simplify image format conversions within scripting environments. Instead of requiring users to manually determine and invoke the correct converter (e.g., giftoppm for GIF, jpegtopnm for JPEG), anytopnm was created to automate this process. It represents an abstraction layer over a large collection of specialized Netpbm converters, embodying the Unix philosophy of small, specialized tools working together. This design has made it a stable and widely used utility for interoperability between diverse image formats in command-line workflows.

pnm(5), ppm(1), pbm(1), pgm(1), netpbm(1), jpegtopnm(1), pngtopnm(1), giftoppm(1), tifftopnm(1), xbmtopbm(1), xpmtoppm(1)