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

The diffimg command is a powerful utility used to calculate the intersection or difference between two images. Typically used in the field of computer graphics and image processing, diffimg helps users identify and visualize the differences between two image files. This can be especially useful for tasks such as regression testing for graphic user interfaces, verifying image updates, or simply finding pixel-level differences between two visuals. The tool supports various image formats, including .png, .gif, .jpg, and .ps.

Use case 1: Calculate the intersection between images and output an image where each pixel is the difference between corresponding pixels in input images

Code:

diffimg path/to/input_image1.ext path/to/input_image2.ext path/to/output_image.ext

Motivation:

The primary motivation for using this example is to perform visual testing in scenarios where pixel-perfect accuracy between two image outputs is crucial. This is often necessary in software development and testing, especially within user interface environments where changes to a graphical representation must be evaluated. For instance, when a developer updates an application’s interface, they may need to ensure that no unintended changes have occurred to visual elements. By using diffimg, testers can directly compare two versions of an image to spot deviations introduced by recent updates.

Explanation:

• path/to/input_image1.ext: This argument refers to the path and filename of the first image you wish to compare. It acts as the baseline image against which the second image will be compared.

• path/to/input_image2.ext: This argument specifies the path and filename of the second image, which is the image containing the changes that need to be assessed against the baseline from the first image.

• path/to/output_image.ext: This final argument defines where the output image, representing the differences between the two input images, will be saved. Each pixel in this output image is computed by subtracting the corresponding pixel values of the second image from the first, highlighting any discrepancies between the two images.

Example Output:

Imagine two version images of a website’s homepage—homepage_v1.png and homepage_v2.png. Using the diffimg command, the output image (let’s say homepage_diff.png) will contain pixels that visually show the differences between the two versions. These differences may include changes in text placements, color variations, or any added or removed graphical element. The resulting image will help easily identify these modifications for further analysis or confirmation before deployment.