How to use the command `pnmscalefixed` (with examples)
Description: The pnmscalefixed command is a part of the Netpbm package, and it allows you to scale a PNM (Portable aNyMap) image quickly with possibly reduced quality. It provides several options to modify the dimensions and aspect ratio of the image. The command is useful when you need to resize images while maintaining their original format and quality.
Use case 1: Scale an image to specific dimensions
Code:
pnmscalefixed -width <width> -height <height> <path/to/input.pnm> > <path/to/output.pnm>
Motivation: This use case is useful when you need to resize an image to specific dimensions. For example, if you have an image that is too large and you want to reduce it to a specific width and height without distorting the aspect ratio, you can use this command.
Explanation:
-width <width>: Specifies the desired width of the output image.-height <height>: Specifies the desired height of the output image.<path/to/input.pnm>: Specifies the path to the input PNM file.<path/to/output.pnm>: Specifies the path where the scaled image will be saved.
Example output:
Suppose we have an input image input.pnm with a width of 800 pixels and a height of 600 pixels. We want to scale it to a width of 400 pixels and a height of 300 pixels.
pnmscalefixed -width 400 -height 300 input.pnm > output.pnm
The above command will create a scaled image named output.pnm with a width of 400 pixels and a height of 300 pixels while preserving the aspect ratio of the original image.
Use case 2: Scale an image while maintaining the aspect ratio
Code:
pnmscalefixed -width <width> <path/to/input.pnm> > <path/to/output.pnm>
Motivation: This use case is useful when you want to resize an image by specifying only the width while keeping the aspect ratio intact. It allows you to scale an image without distorting its proportions.
Explanation:
-width <width>: Specifies the desired width of the output image.<path/to/input.pnm>: Specifies the path to the input PNM file.<path/to/output.pnm>: Specifies the path where the scaled image will be saved.
Example output:
Suppose we have an input image input.pnm with a width of 800 pixels and a height of 600 pixels. We want to scale it to a width of 400 pixels while maintaining the aspect ratio.
pnmscalefixed -width 400 input.pnm > output.pnm
The above command will create a scaled image named output.pnm with a width of 400 pixels, keeping the height proportional to the original image.
Use case 3: Scale an image using specified scaling factors
Code:
pnmscalefixed -xscale <x_factor> -yscale <y_factor> <path/to/input.pnm> > <path/to/output.pnm>
Motivation: This use case is useful when you want to scale an image by specifying the scaling factors for both the width and height. It provides flexibility to resize an image by adjusting both dimensions independently.
Explanation:
-xscale <x_factor>: Specifies the scaling factor for the width of the output image.-yscale <y_factor>: Specifies the scaling factor for the height of the output image.<path/to/input.pnm>: Specifies the path to the input PNM file.<path/to/output.pnm>: Specifies the path where the scaled image will be saved.
Example output:
Suppose we have an input image input.pnm with a width of 800 pixels and a height of 600 pixels. We want to scale it using a scaling factor of 0.5 for the width and 1.2 for the height.
pnmscalefixed -xscale 0.5 -yscale 1.2 input.pnm > output.pnm
The above command will create a scaled image named output.pnm with a width of 400 pixels (800 * 0.5) and a height of 720 pixels (600 * 1.2) by applying the provided scaling factors to the width and height of the original image.
Conclusion:
The pnmscalefixed command is a convenient tool for scaling PNM images quickly and efficiently. It provides options to resize images while preserving aspect ratio or independently adjusting the width and height using scaling factors. Whether you need to resize images for web applications, presentations, or any other purpose, this command allows you to achieve the desired dimensions with reduced quality, if necessary.
