How to use the command `ppmntsc` (with examples)

The ppmntsc command is used to make the RGB colors in a PPM image compatible with NTSC or PAL color systems. It can also provide information about the number of illegal pixels in the image and allows the user to output only legal, illegal, or corrected pixels.

Use case 1: Make the RGB colors in a PPM image compatible with NTSC color systems

Code:

ppmntsc path/to/input_file.ppm > path/to/output_file.ppm

Motivation: By using this command, the RGB colors in a PPM image can be transformed to be compatible with NTSC color systems. This is useful when working with images that need to be displayed on devices supporting NTSC standards, such as old television sets.

Explanation:

• ppmntsc: The command name.
• path/to/input_file.ppm: The path to the input PPM image file. Replace path/to with the actual file path.
• > path/to/output_file.ppm: The path to the output PPM image file. Replace path/to with the desired file path.

Example output: The RGB colors in the input PPM image will be transformed to comply with NTSC color systems and the resulting image will be saved at the specified output file path.

Use case 2: Make the RGB colors in a PPM image compatible with PAL color systems

Code:

ppmntsc --pal path/to/input_file.ppm > path/to/output_file.ppm

Motivation: When working with images that need to be displayed on devices supporting PAL color systems, using this command can ensure that the RGB colors in a PPM image are transformed to be compatible with PAL standards.

Explanation:

• --pal: Specifies that the output colors should be compatible with PAL color systems.
• path/to/input_file.ppm: The path to the input PPM image file.
• > path/to/output_file.ppm: The path to the output PPM image file.

Example output: The RGB colors in the input PPM image will be transformed to comply with PAL color systems and the resulting image will be saved at the specified output file path.

Use case 3: Print the number of illegal pixels in the input image to stderr

Code:

ppmntsc --verbose path/to/input_file.ppm > path/to/output_file.ppm

Motivation: This use case is helpful when needing to know how many illegal pixels exist in the input image. It provides information about the number of pixels that are not compatible with the NTSC or PAL color systems.

Explanation:

• --verbose: Enables the output of additional information, including the number of illegal pixels.
• path/to/input_file.ppm: The path to the input PPM image file.
• > path/to/output_file.ppm: The path to the output PPM image file.

Example output: In addition to the transformed image, the command will print the number of illegal pixels in the input image to stderr.

Use case 4: Output only legal/illegal/corrected pixels, set other pixels to black

Code:

ppmntsc --legalonly|illegalonly|correctedonly path/to/input_file.ppm > path/to/output_file.ppm

Motivation: This use case allows the user to generate images where only legal, illegal, or corrected pixels are visible while setting other pixels to black. It can be useful for analyzing and visualizing the changes made to the image colors.

Explanation:

• --legalonly|illegalonly|correctedonly: Specifies that only legal, illegal, or corrected pixels should be visible in the output image. Choose one of these options.
• path/to/input_file.ppm: The path to the input PPM image file.
• > path/to/output_file.ppm: The path to the output PPM image file.

Example output: The command will generate an image where only the specified type of pixels (legal, illegal, or corrected) are visible, while all other pixels are set to black. This allows for a clear visualization of the selected pixels.

Conclusion:

The ppmntsc command provides a range of useful functionalities for managing the color compatibility of PPM images with NTSC and PAL color systems. It allows for simple transformations as well as more detailed outputs for analysis purposes.