How to use the command pnmtosgi (with examples)

The pnmtosgi command is used to convert a PNM (Portable Anymap) file to an SGI (Silicon Graphics Image) file. This command is part of the Netpbm package, which provides a set of utilities for manipulating and converting various image file formats.

Use case 1: Convert a PNM image to an SGI image

Code:

pnmtosgi path/to/input.pnm > path/to/output.sgi

Motivation: This use case is useful when you have a PNM image file that you want to convert to the SGI format. The converted SGI file can then be used in applications or tools that require this specific file format.

Explanation:

• pnmtosgi - This is the command that converts the PNM file to SGI format.
• path/to/input.pnm - This is the path to the input PNM file that you want to convert.
• path/to/output.sgi - This is the path to the output SGI file where the converted image will be saved. The > operator is used to redirect the output of the command to the specified file.

Example output: The command pnmtosgi path/to/input.pnm > path/to/output.sgi will convert the input.pnm file to SGI format and save it as output.sgi in the specified path.

Use case 2: Specify whether or not compression should be used

Code:

pnmtosgi -verbatim|rle path/to/input.pnm > path/to/output.sgi

Motivation: Compression can significantly reduce the size of the resulting SGI image file. However, in some cases, it may be necessary to disable compression to preserve the image quality or optimize for a specific use case. This use case allows you to specify whether or not compression should be used during the conversion process.

Explanation:

• -verbatim|rle - This argument allows you to specify the compression type to be used in the output SGI file.
  • verbatim specifies that no compression should be used.
  • rle specifies that Run-Length Encoding (RLE) compression should be used. RLE is a simple form of lossless data compression that is efficient for images with large areas of uniform color.
• path/to/input.pnm - This is the path to the input PNM file that you want to convert.
• path/to/output.sgi - This is the path to the output SGI file where the converted image will be saved. The > operator is used to redirect the output of the command to the specified file.

Example output: The command pnmtosgi -rle path/to/input.pnm > path/to/output.sgi will convert the input.pnm file to SGI format and apply RLE compression to the resulting image before saving it as output.sgi.

Use case 3: Write the specified string into the SGI image header’s imagename field

Code:

pnmtosgi -imagename string path/to/input.pnm > path/to/output.sgi

Motivation: This use case allows you to embed a custom string into the imagename field of the SGI image header. This can be useful for adding metadata or identifying the image with a specific name or label.

Explanation:

• -imagename string - This argument specifies the string that you want to write into the imagename field of the SGI image header. Replace string with the desired value.
• path/to/input.pnm - This is the path to the input PNM file that you want to convert.
• path/to/output.sgi - This is the path to the output SGI file where the converted image will be saved. The > operator is used to redirect the output of the command to the specified file.

Example output: The command pnmtosgi -imagename "My Image" path/to/input.pnm > path/to/output.sgi will convert the input.pnm file to SGI format and write the string “My Image” into the imagename field of the resulting SGI image header. The converted image will be saved as output.sgi.