How to use the command pamscale (with examples)

This article will provide examples of different use cases of the pamscale command.

Description:

The pamscale command is used to scale an Netpbm image. It allows users to resize images to specific dimensions, change their width and height by a specified factor, or fit/fill them within a bounding box while preserving the aspect ratio.

Use case 1: Scale an image to specified dimensions

Code:

pamscale -width width -height height path/to/input.pam > path/to/output.pam

Motivation: This use case is ideal when you want to resize an image to exact dimensions. It can be useful when you need images to fit specific requirements, such as for a website or a printed publication.

Explanation:

• -width: Specifies the desired width of the output image.
• -height: Specifies the desired height of the output image.
• path/to/input.pam: The path to the input image file.
• > path/to/output.pam: Redirects the output to the specified file path.

Example Output: If we have an image with dimensions 800x600 and we want to scale it to 400x300, the command would be:

pamscale -width 400 -height 300 input.pam > output.pam

Use case 2: Scale an image while keeping the aspect ratio

Code:

pamscale -width width path/to/input.pam > path/to/output.pam

Motivation: This use case comes in handy when you want to adjust the width of an image while maintaining its original aspect ratio. It ensures that the proportions of the image are preserved, avoiding distortion.

Explanation:

• -width: Specifies the desired width of the output image.
• path/to/input.pam: The path to the input image file.
• > path/to/output.pam: Redirects the output to the specified file path.

Example Output: If we have an image with dimensions 800x600 and we want to scale it to a width of 400 pixels, the command would be:

pamscale -width 400 input.pam > output.pam

Use case 3: Scale an image by specified factors

Code:

pamscale -xscale x_factor -yscale y_factor path/to/input.pam > path/to/output.pam

Motivation: This use case allows users to change the dimensions of an image by specific factors. It is useful when you want to increase or decrease the size of an image by a certain factor without specifying exact dimensions.

Explanation:

• -xscale: Specifies the scaling factor for the width of the output image.
• -yscale: Specifies the scaling factor for the height of the output image.
• path/to/input.pam: The path to the input image file.
• > path/to/output.pam: Redirects the output to the specified file path.

Example Output: If we have an image with dimensions 800x600 and we want to scale it by a factor of 0.5 on the x-axis and 0.3 on the y-axis, the command would be:

pamscale -xscale 0.5 -yscale 0.3 input.pam > output.pam

Use case 4: Fit an image within a bounding box while preserving aspect ratio

Code:

pamscale -xyfit bbox_width bbox_height path/to/input.pam > path/to/output.pam

Motivation: This use case is useful when you want to resize an image to fit within a specified bounding box while maintaining its original aspect ratio. It ensures that the entire image fits within the given dimensions without cropping or distorting it.

Explanation:

• -xyfit: Specifies the width and height of the bounding box to fit the image into.
• bbox_width: The desired width of the bounding box.
• bbox_height: The desired height of the bounding box.
• path/to/input.pam: The path to the input image file.
• > path/to/output.pam: Redirects the output to the specified file path.

Example Output: If we have an image with dimensions 800x600 and we want to fit it into a bounding box of 500x400, the command would be:

pamscale -xyfit 500 400 input.pam > output.pam

Use case 5: Fill a bounding box with an image while preserving aspect ratio

Code:

pamscale -xyfill box_width box_height path/to/input.pam > path/to/output.pam

Motivation: This use case is suitable when you want to resize an image to fill a specified bounding box while maintaining its original aspect ratio. It guarantees that the entire bounding box is covered by the image, which may result in cropping part of the image.

Explanation:

• -xyfill: Specifies the width and height of the bounding box to fill with the image.
• box_width: The desired width of the bounding box.
• box_height: The desired height of the bounding box.
• path/to/input.pam: The path to the input image file.
• > path/to/output.pam: Redirects the output to the specified file path.

Example Output: If we have an image with dimensions 800x600 and we want to fill a bounding box of 1000x800, the command would be:

pamscale -xyfill 1000 800 input.pam > output.pam

Conclusion:

The pamscale command is a versatile tool for scaling Netpbm images. It provides options to resize images to specific dimensions, change their size by factors, and fit/fill them within bounding boxes while maintaining the aspect ratio. Understanding the various use cases of the command helps users efficiently manipulate images according to their requirements.