How to Use the Command 'pnmtorast' (with Examples)

The pnmtorast command is a utility from the Netpbm toolkit designed to convert PNM (Portable Any Map) image files into Sun rasterfiles. The Sun raster format is a bitmap image format originally associated with the Sun Microsystems workstation. This utility can be particularly useful when dealing with legacy systems or specific applications that require images in the Sun raster format. The pnmtorast command provides options to convert PNM images into two forms of Sun raster files: RT_STANDARD and RT_BYTE_ENCODED.

Use Case 1: Convert a PNM image to a RAST image

Code:

pnmtorast path/to/input.pnm > path/to/output.rast

Motivation:

You might want to convert a PNM image to a Sun raster image when working with legacy software systems that require this type of image format, or when sending images to a device that specifically supports Sun raster files. For example, if you’re working with an older imaging system or a specific piece of hardware that only accepts raster images, conversion using pnmtorast ensures compatibility and continued functionality of your workflow.

Explanation:

• pnmtorast: This is the command used for converting a PNM file to a Sun raster file.

• path/to/input.pnm: This is the path to the input file, which should be a PNM file. PNM is a flexible image format and encompasses multiple types, including PBM (bitmap), PGM (grayscale), and PPM (pixel map).

• >: This redirection operator is used to write the output of the command into a file.

• path/to/output.rast: This specifies where the converted Sun raster file will be saved.

Example Output:

Upon executing this command, a new file named output.rast will be created at the specified location. This file will be a Sun raster image converted from the original PNM image, which can be verified by checking the file format or using applications that can open Sun raster images.

Use Case 2: Force either RT_STANDARD or RT_BYTE_ENCODED form for the output

Code:

pnmtorast -standard path/to/input.pnm > path/to/output.rast

or

pnmtorast -rle path/to/input.pnm > path/to/output.rast

Motivation:

This use case is particularly important when the specific format of the Sun raster file is required by your system or application. Different systems might have different requirements regarding image encoding formats. By specifying either -standard or -rle, you gain control over the type of encoding used for the output raster file, ensuring that it meets the specific needs of your application or hardware.

Explanation:

• pnmtorast: This is the command used for converting a PNM file to a Sun raster file.

• -standard: This flag specifies that the output should be in the RT_STANDARD format, which is the traditional uncompressed Sun raster format.

• -rle: This flag specifies the RT_BYTE_ENCODED format, which uses Run-Length Encoding (RLE) for compression, resulting in smaller file sizes, beneficial for storage and transfer efficiency.

• path/to/input.pnm: This is the path to the input PNM file you want to convert.

• >: This redirection operator is used to save the command’s output to a file.

• path/to/output.rast: This represents the location and name where the newly converted Sun raster file will be saved.

Example Output:

When using -standard, the output output.rast will be a typical, uncompressed Sun raster file, which can be larger in size. In contrast, using -rle will result in a file that is compressed using Run-Length Encoding, often resulting in a smaller file size without loss of quality, suitable for systems where storage space is a concern.

Conclusion:

The pnmtorast command is a powerful conversion tool for anyone needing to work with Sun raster images. Whether for compatibility with legacy systems or specific application requirements, understanding how to use this command with its various options allows for flexible image processing workflows and efficient integration with different systems requiring Sun raster files.