How to use the command "ppmdither" (with examples)
1: Reduce the number of colors in an image
ppmdither path/to/image.ppm > path/to/file.ppm
Motivation: One common use case for the ppmdither command is to reduce the number of colors in an image. This can be useful when working with images that have a large number of colors or when trying to optimize the size of an image file. By applying dithering, which distributes the error resulting from color reduction across neighboring pixels, the resulting image can maintain visual quality while using fewer colors.
Explanation: In this use case, we provide the path to the input PPM image file (path/to/image.ppm) and redirect the output to a new PPM file (path/to/file.ppm). The > symbol is used to redirect the output of the command to a file.
Example Output: The command will read the input image, apply dithering to reduce the number of colors, and save the result to the specified file. The resulting file will contain the same image but with a reduced color palette.
2: Specify the desired number of shades for each primary color
ppmdither -red 2 -green 3 -blue 2 path/to/image.ppm > path/to/file.ppm
Motivation: Sometimes we may want to have finer control over the number of colors used in specific color channels. By specifying the desired number of shades for each primary color (red, green, and blue), we can achieve a desired visual effect or match a particular color palette.
Explanation: In this use case, we use the -red, -green, and -blue options followed by the desired number of shades for each primary color. For example, -red 2 specifies 2 shades of red, -green 3 specifies 3 shades of green, and -blue 2 specifies 2 shades of blue. The command will apply dithering based on the specified shades for each color channel.
Example Output: Running this command will read the input image, reduce the number of colors according to the specified shades, and save the result to the specified file. The resulting image will have the specified number of shades for each primary color, resulting in a visually distinct output.
3: Specify the dimensions of the dithering matrix
ppmdither -dim 2 path/to/image.ppm > path/to/file.ppm
Motivation: The dithering matrix controls how the error is distributed when reducing the number of colors in an image. By specifying the dimensions of the dithering matrix, we can adjust the level of dithering and influence the visual quality of the resulting image.
Explanation: In this use case, we use the -dim option followed by a number to specify the dimensions of the dithering matrix. For example, -dim 2 specifies a 2x2 dithering matrix. The command will apply dithering based on the specified dimensions of the dithering matrix.
Example Output: When running this command, the input image will be read, and the number of colors will be reduced using dithering with the specified dimensions of the dithering matrix. The resulting image will have a different visual quality depending on the chosen dimensions of the dithering matrix.
