Compare Image Quality
You have 2 equal images in files, you don’t have a reference highest quality image and you want to keep the better one of the two? - SE
- Resize to the bigger size & re-compress both images with exactly same quality preset, grayscale conversion, using JPEG or better algorithm.
- Compare the file sizes.
- Erase the files and keep the better picture (coresponding to the bigger file).
Explanation
Often the image compression preset is different for the different files so the initial sizes cannot speak for the quality. That’s why we re-compress them with the same preset and software. We resize to equal size so the compressor decisions are made based on the detail level of the 2 images. Not always the bigger one has the higher detail.
When this will fail
if one of the images is with applied noise filter - some photographers add noise when retoutching their photos to increase their “ART” value. The noise is hardly compressible and is perceived by the JPEG codec/compressor as higher level of detail, so will yield a bigger file.