Images-diff

Description

Compare images and report the differences.

Given images a.jpeg, b.jpeg, and c.jpeg, the program performs the following comparisons:

• a.jpeg and b.jpeg
• b.jpeg and c.jpeg

The differences can be computed using MSE (mean error squared) or SSIM (structural similarity index measure) as the metric.

Requirements

• Node.js (>=22).
• ImageMagick (>=7.1), when MSE is used as the metric.
• FFmpeg (>=6.1), when SSIM is used as the metric.

Installation

0. npm clean-install --omit=dev

Configuration

Create a configuration file with the name .env. The configuration file controls the following:

• MAGICK_PATH: Path of ImageMagick.
  • If magick (for UNIX/ Linux system) or magick.exe is in the PATH environment variable, it is not necessary to specify the full path, the executable name itself is sufficient.
• FFMPEG_PATH: Path of FFmpeg.
  • If ffmpeg (for UNIX/ Linux system) or ffmpeg.exe is in the PATH environment variable, it is not necessary to specify the full path, the executable name itself is sufficient.
• METRIC: Comparison metric. Acceptable values are mse and ssim.
• DIFF_THRESHOLD: Difference threshold. If the difference is beyond the threshold, the comparison pair is considered as abnormal.
• ABNORMAL_IMAGES_DIRECTORY: The directory to be created for abnormal images. If specified, the directory will be created under the input directory.
• Set all of the following to crop to the area to be inspected:
  • CROP_WIDTH: The width of a cropped image.
  • CROP_HEIGHT: The height of a cropped image.
  • CROP_OFFSET_X: The offset from the left of the original image.
  • CROP_OFFSET_Y: The offset from the top of the original image.

An example, .env.template, is provided as a reference.

Examples

Assume the directory /path/to/images contains some images for comparisons and using SSIM as the metric, execute:

node index.js /path/to/images

The output will be similar to the following:

[OKAY] 01.png, 02.png: 1
[OKAY] 02.png, 03.png: 1
[OKAY] 03.png, 04.png: 1
[WARN] 04.png, 05.png: 0.250075

The output shows that:

• The difference between 01.png and 02.png is 0 and within threshold.
• The difference between 02.png and 03.png is 0 and within threshold.
• The difference between 03.png and 04.png is 0 and within threshold.
• The difference between 04.png and 05.png is 0.250075 and below threshold.

If ABNORMAL_IMAGES_DIRECTORY is specified, 04.png and 05.png will be copied to the directory.

If the images cannot be compared, for example due to corrupted file headers, and ImageMagick or FFmpeg is unable to complete the comparison, an error may be printed on stderr. For example:

Compare program exited with code 1 when comparing 01.avif and 02.avif.

In such case, the differences between the images will be set to null. For example:

[WARN] 01.avif, 02.avif: null

The involved files will be copied to ABNORMAL_IMAGES_DIRECTORY.

License

The BSD 3-Clause License