pnmtotiffcmyk

Convert a PNM image to a CMYK encoded TIFF

$ pnmtotiffcmyk [path/to/input_file.pnm] > [path/to/output_file.tiff]

$ pnmtotiffcmyk -[none|packbits|lzw] [path/to/input_file.pnm] > [path/to/output_file.tiff]

$ pnmtotiffcmyk -[msb2lsb|lsb2msb] [path/to/input_file.pnm] > [path/to/output_file.tiff]

pnmtotiffcmyk [-c compression] [-r rowsperstrip] [-l] [-f] [-o offset] [-x xres] [-y yres] [-u units] [-w] [pnmfile]

-c compression
    Specifies the TIFF compression method. Common options include none, packbits, lzw, zip, and jpeg.

-r rowsperstrip
    Sets the number of rows per strip in the output TIFF file. This affects how the image data is stored and read.

-l
    Enables LZW compression. This is equivalent to using -c lzw.

-f
    Uses FillOrder LSB2MSB (Least Significant Bit to Most Significant Bit) instead of the default MSB2LSB (Most Significant Bit to Least Significant Bit). This can affect how pixel bits are ordered.

-o offset
    Specifies a byte offset for the image data within the TIFF file. Useful for specific file structures.

-x xres
    Sets the X resolution of the image in pixels per unit.

-y yres
    Sets the Y resolution of the image in pixels per unit.

-u units
    Defines the units for resolution. Possible values are inch, cm, or none.

-w
    Prints warnings for common usage mistakes or unusual conditions, which can be helpful for debugging.

pnmfile
    The input PNM file to convert. If omitted, pnmtotiffcmyk reads from standard input (stdin).

pnmtotiffcmyk is a utility from the Netpbm image processing suite that converts a Portable Anymap (PNM) image into a Tagged Image File Format (TIFF) image using the CMYK color model. PNM images can be Portable Pixmap (PPM) for color, Portable Graymap (PGM) for grayscale, or Portable Bitmap (PBM) for black and white. CMYK (Cyan, Magenta, Yellow, Black) is the subtractive color model primarily used for commercial printing, where colors are created by applying various inks.

This command is crucial in workflows that prepare raster images for print. It takes an RGB (or grayscale) input from a PNM file (or standard input) and performs a mathematical conversion to CMYK values. While it does not incorporate advanced color management features like ICC profiles, it provides a foundational step for producing print-ready TIFFs. It supports various TIFF compression schemes and allows specifying output parameters like resolution, strips, and byte order.

Input Format: pnmtotiffcmyk strictly requires a PNM (PBM, PGM, or PPM) image as input. Other image formats must first be converted to PNM using tools like anytopnm.

Color Conversion Limitations: The RGB-to-CMYK conversion performed by this command is a direct mathematical approximation and does not utilize ICC color profiles. This means that the resulting CMYK values may not precisely match specific print industry standards or desired color outputs without further color management in the print workflow.

Grayscale Handling: When converting a PGM (grayscale) input, the output will be a CMYK TIFF where the Cyan, Magenta, and Yellow channels are zero, and the Black channel represents the grayscale intensity.

The command primarily handles the conversion from an implicit RGB (for PPM files) or grayscale (for PGM files) color space to CMYK. It's important to understand that this is a direct channel-to-channel transformation, not a perceptually accurate color space conversion based on spectrophotometric data or ICC profiles. Users requiring precise color matching for professional printing should either perform color management upstream with other tools or apply it post-conversion.

pnmtotiffcmyk is often used as the final step in a Netpbm image processing pipeline. For instance, an image from an arbitrary format might first be converted to PNM (e.g., giftoppm | ppmtogray | pnmtotiffcmyk) before being output as a CMYK TIFF. This modularity is a hallmark of the Netpbm design philosophy, allowing for flexible and powerful scripting of image operations.

pnmtotiffcmyk is an integral part of the widely used Netpbm package, a collection of graphics programs originating from Pbmplus developed by Jef Poskanzer in 1988. Netpbm was designed to be a modular toolkit, enabling users to chain simple, specialized commands together via pipes to achieve complex image manipulations. The inclusion of pnmtotiffcmyk specifically addresses the need for command-line tools capable of preparing raster images for commercial printing workflows, where the CMYK color model is standard. Its development reflects the evolution of desktop publishing and the continuous demand for robust, automatable image processing utilities.

netpbm(1), pnmtotiff(1), anytopnm(1), pnm(5), tiff(1)