netpbm

Netpbm is a collection of individual programs, not a single command with universal syntax. Its tools are typically used following this pattern:
program_name [options] [input_file] > output_file

Many Netpbm programs are designed to read image data from standard input (if no input_file is specified) and write the processed image to standard output. This facilitates piping one tool's output directly into another's input.

Example: jpegtopnm input.jpg | pnmscale 0.5 | pnmtopng > output.png

(No universal parameters for the Netpbm suite itself)
    The netpbm utility is a suite of hundreds of distinct programs, each with its own set of specific command-line parameters and options. Therefore, there are no universal parameters that apply across the entire Netpbm suite.

However, common categories of parameters found across individual Netpbm tools include:
Input/Output options: For specifying input files, output destinations, or indicating standard I/O usage.
Transformation options: Such as dimensions for scaling (e.g., -width, -height for pnmscale), angles for rotation, or coordinates for cropping.
Color and Pixel manipulation: Options related to color depths, grayscale conversion (e.g., -greyscale for ppmtopgm), or specific pixel values.
Format-specific options: Parameters relevant to the particular image format being converted to or from (e.g., compression quality for pnmtojpeg).
Help/Version: Most tools support standard options like -help or -version.

Netpbm is a powerful and versatile suite of over 220 command-line utilities for manipulating graphic images. It serves as a foundational toolkit for image processing in Unix-like environments. Its primary function involves converting various image formats (such as JPEG, PNG, TIFF, GIF) into its own set of intermediate formats – PBM (Portable BitMap), PGM (Portable GrayMap), and PPM (Portable PixMap) – and back again. These intermediate formats are simple, uncompressed, and designed for easy processing.

The strength of Netpbm lies in its modularity, adhering to the Unix philosophy: small, single-purpose tools that perform one specific task well. Users typically chain these tools together using pipes to create complex image processing workflows, enabling operations like scaling, cropping, rotating, color adjustments, and much more. It's widely used in scripts, web servers, and automated image processing pipelines.

Steep Learning Curve: Effectively using Netpbm requires understanding its many individual tools and how to combine them via command-line pipes, which can be less intuitive for beginners.
Uncompressed Intermediate Files: The Netpbm formats (PBM, PGM, PPM) are uncompressed. When not piped, intermediate files can be very large, consuming significant disk space.
Command-line Only: Netpbm is entirely command-line driven, lacking a graphical user interface, which may be a limitation for some users.
Basic Functionality: While powerful for pixel-level manipulation and format conversion, it does not offer advanced image editing features found in software like GIMP or Photoshop (e.g., layers, complex filters, drawing tools).

The Netpbm project originated in the late 1980s, initially developed by Jef Poskanzer and known as PBMPlus. It quickly gained popularity due to its robust functionality and adherence to the Unix philosophy of small, single-purpose tools. In the mid-1990s, as the suite expanded beyond just PBM (Portable BitMap) utilities to include PGM and PPM, it was renamed Netpbm. The project has been continuously maintained and developed by various contributors, solidifying its place as a staple toolkit for image processing in Unix-like operating systems. Its design principles have influenced many subsequent command-line tools.

pnm(5), anytopnm(1), pnmtojpeg(1), jpegtopnm(1), pnmscale(1), pnmcrop(1), convert(1) (ImageMagick), mogrify(1) (ImageMagick), identify(1) (ImageMagick)