How to Add Borders to PNM Images Using the 'pnmmargin' Command (with examples)

The pnmmargin command is part of the Netpbm toolkit, a suite of programs used for manipulating PNM (Portable AnyMap) images. PNM is a family of formats including PBM (Portable Bitmap), PGM (Portable Graymap), and PPM (Portable Pixmap). The pnmmargin utility specifically adds a border to a PNM image, which can be useful in preparing images for presentations, highlighting important content, or simply enhancing the visual aesthetics.

Use Case 1: Add a Border of the Specified Size to a PNM Image

Code:

pnmmargin 10 path/to/image.pnm > path/to/output.pnm

Motivation:

Adding a border to an image is a common task in graphic design and photo editing. It helps in distinguishing an image from the surrounding content, improving its visual appeal. For instance, when dealing with presentations or web content, having a border can help focus the viewer’s attention or integrate the image seamlessly with the background. Specifically, specifying a border size allows for precise adjustments depending on the aesthetic or functional needs of the image.

Explanation:

• pnmmargin: This is the command used to add a border around a PNM image.
• 10: This argument specifies the width of the border, in pixels, that will be added to all sides of the image. A value of 10 indicates that the border will be 10 pixels wide.
• path/to/image.pnm: The path to the input image in PNM format that you want to add the border to.
• >: This redirect operator is used to save the output of the command (the modified image) into a new file.
• path/to/output.pnm: The path where you want to save the output image with the added border.

Example Output:

Imagine the input image is a simple grayscale square of 50x50 pixels. After executing the above command, the output image will be 70x70 pixels, with the original content centered and surrounded by a uniform 10-pixel border on all sides.

Use Case 2: Specify the Color of the Border

Code:

pnmmargin -color black 15 path/to/image.pnm > path/to/output.pnm

Motivation:

Customizing the color of an image border is essential when aiming for specific color themes or contrasts. For instance, when creating marketing materials or social media content, the border color can be tailored to match branding guidelines or to provide an aesthetically pleasing contrast to the main image. Detailed control over the border’s color enhances the versatility and integration of images within various design frameworks.

Explanation:

• pnmmargin: Initiates the command to add a border to the PNM image.
• -color black: This option specifies the color of the border. In this case, black indicates that the border will be black. The command supports different colors which can be defined using names or numerical RGB values.
• 15: Defines the border’s width to be 15 pixels for each side of the image.
• path/to/image.pnm: Points to the location of the input PNM image file.
• >: Redirects the output to save the produced image into a file.
• path/to/output.pnm: Indicates where the modified image with the specified border should be saved.

Example Output:

Assuming the input image is the same 50x50 pixel grayscale square, after running this command, the resulting output image would be 80x80 pixels. The additional 15 pixels on each side would be filled with the color black, creating a dark frame around the original image content.

Conclusion:

The pnmmargin command is a straightforward yet powerful tool for adding borders to PNM images with customizable sizes and colors. These features can significantly enhance the presentation of images, making them more suitable for a variety of contexts, from professional presentations to casual displays. By adjusting the border’s size and color, users can achieve the desired emphasis and style for their images, ensuring they both stand out and complement their surroundings effectively.