CODEWITHSUNDEEP
image-processingffmpegimagemagickssim
jamacoe
jamacoe

Reputation: 549

What is the correct way to calculate SSIM?

On Windows 10, I have installed ImageMagick, Version 7.1.1-Q16-HDRI.

I have a high resolution .png image that I convert to jpg with 75% quality:

magick myImage.png -quality 75 myImage.jpeg

Now I want to calculate SSIM to judge the quality of the .jpeg in comparison to the original .png.

First, I am using ffmpeg.exe version 4.2.3 from the very same ImageMagick installation:

ffmpeg.exe -i myImage.jpeg -i myImage.png -lavfi ssim=stats_file=ssim_logfile.txt -f null -

Results in ssim_logfile.txt:

n:1 Y:0.959684 U:0.957603 V:0.976335 All:0.962112 (14.215018)

So I assume that the SSIM value has been calculated as 0.962112

Now I'll use magick to calculate the same metric:

magick myImage.jpeg myImage.png -metric SSIM -compare -format "%[distortion]" info:

Output is:

0.925167

That's a huge difference! So I think I'm making an error here with one or the other way.

What is the correct way to calculate SSIM?

Upvotes: 1

Views: 373

Answers (0)

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