How to use the command rawtoppm (with examples)

The rawtoppm command is used to convert a raw RGB stream into a PPM image. It can also handle various options to customize the conversion process.

Use case 1: Convert a raw RGB stream to a PPM image

Code:

rawtoppm width height path/to/image.raw > path/to/output.ppm

Motivation for using this example: Suppose you have a raw RGB stream captured from a camera and you want to convert it into a PPM image format for easy visualization or further processing. This command allows you to accomplish that.

Explanation of arguments:

• width and height: These arguments specify the dimensions of the image.
• path/to/image.raw: This argument specifies the path to the input raw RGB stream file.
• path/to/output.ppm: This argument specifies the path to the output PPM image file.

Example output: The raw RGB stream is converted into a PPM image and saved at the specified output file path.

Use case 2: Convert a raw RGB stream in which the pixels come bottom-first instead of top-first to a PPM image

Code:

rawtoppm width height path/to/image.raw | pamflip -tb > path/to/output.ppm

Motivation for using this example: In some cases, the raw RGB stream may have a different pixel ordering where the pixels come in a bottom-first format instead of the usual top-first format. This command, in combination with pamflip, allows you to correct the pixel ordering and convert it into a PPM image.

Explanation of arguments:

• pamflip -tb: This part of the command flips the image vertically, correcting the bottom-first pixel ordering.

Example output: The raw RGB stream with corrected pixel ordering is converted into a PPM image and saved at the specified output file path.

Use case 3: Ignore the first n bytes of the specified file

Code:

rawtoppm width height -headerskip n path/to/image.raw > path/to/output.ppm

Motivation for using this example: Sometimes, the raw RGB stream may have some header information at the beginning of the file that is not required for the conversion. This command allows you to skip the specified number of bytes from the beginning of the file.

Explanation of arguments:

• -headerskip n: This option skips the first n bytes of the input file before processing.

Example output: The raw RGB stream with the specified number of bytes skipped is converted into a PPM image and saved at the specified output file path.

Use case 4: Ignore the last m bytes of each row in the specified file

Code:

rawtoppm width height -rowskip m path/to/image.raw > path/to/output.ppm

Motivation for using this example: In certain scenarios, the raw RGB stream may contain some additional padding or metadata at the end of each row that is not required for the conversion. This command allows you to skip the specified number of bytes from the end of each row.

Explanation of arguments:

• -rowskip m: This option skips the last m bytes of each row in the input file before processing.

Example output: The raw RGB stream with the specified number of bytes skipped from each row is converted into a PPM image and saved at the specified output file path.

Use case 5: Specify the order of color components for each pixel

Code:

rawtoppm width height -rgb|rbg|grb|gbr|brg|bgr path/to/image.raw > path/to/output.ppm

Motivation for using this example: The raw RGB stream may have a different order of color components (red, green, and blue) for each pixel. This command allows you to specify the desired order of color components.

Explanation of arguments:

• -rgb|rbg|grb|gbr|brg|bgr: This option specifies the order of color components for each pixel. You can choose from six different combinations: RGB, RBG, GRB, GBR, BRG, and BGR.

Example output: The raw RGB stream with the specified color component order is converted into a PPM image and saved at the specified output file path.

Conclusion:

The rawtoppm command provides a powerful tool for converting raw RGB streams into PPM image files. With its various options, you can customize the conversion process to suit your specific needs, such as handling different pixel orders and skipping unnecessary bytes. This flexibility makes it a valuable command for working with raw RGB data.