How to use the command pstopnm (with examples)

The pstopnm command is used to convert PostScript files to PNM images. PNM is a format for storing monochrome (pbm), grayscale (pgm), or color (ppm) images that are widely supported by various image processing tools. This command provides several options to customize the output, such as selecting specific pages and setting the resolution.

Use case 1: Convert a PS file to PNM images

Code:

pstopnm path/to/file.ps

Motivation: You want to convert a PostScript file to PNM images. This could be useful if you need to process or display the images using tools that support the PNM format.

Explanation: The command pstopnm is followed by the path to the PostScript file (path/to/file.ps). This will convert the entire file to PNM images, with each page of the input file saved as a separate image.

Example output: The command will generate multiple PNM files named file-1.ppm, file-2.ppm, …, one for each page of the input file.

Use case 2: Explicitly specify the output format

Code:

pstopnm -pbm|pgm|ppm path/to/file.ps

Motivation: You want to choose the specific format of the output PNM images. For example, you may want to convert a PostScript file to a grayscale PGM image instead of the default color PPM image.

Explanation: The command pstopnm is followed by the option -pbm, -pgm, or -ppm to specify the desired output format. -pbm generates monochrome (black and white) images, -pgm generates grayscale images, and -ppm generates color images. The path to the PostScript file (path/to/file.ps) is then provided.

Example output: The command will generate PNM files of the specified format, with their names following the same convention as in the previous use case.

Use case 3: Specify the resolution of the output

Code:

pstopnm -dpi n path/to/file.ps

Motivation: You want to adjust the resolution of the output PNM images. By default, the resolution is set to 72 dots per inch (dpi), but you may need a higher or lower resolution depending on your application.

Explanation: The command pstopnm is followed by the option -dpi, which must be followed by the desired resolution n in dots per inch. The path to the PostScript file (path/to/file.ps) is then provided.

Example output: The command will generate PNM files with the specified resolution, using the same naming convention as in the first use case.

Conclusion:

The pstopnm command is a powerful tool for converting PostScript files to PNM images. By using different options, you can customize the output format and resolution according to your needs. Whether you want to work with monochrome, grayscale, or color images, or adjust the resolution, pstopnm provides the flexibility required for your image processing tasks.