Album Art resize action altering B&W embedded art

[JohnIV]

Hi, I have found that if I run my series of actions (which includes a 600x600 pixel resize) on a song that has embedded album art that is grayscale, the resize algorithm will appear to decrease the bit depth of the B&W image so it's banded and rough looking. I then have to go in and remove and add the original B&W image to fix it. I have a song here that does it, I'll see if I can attach. Latest MP3Tag 3.22b on Win11 x64.

Original:

[ohrenkino]

I can confirm this behaviour.
I resized the offered original from 500x500 to 400x400 with MP3tag:

and with Acdsee:

See the area at the arms.

[Florian]

Thanks for pointing to that issue. I've experimented and tried to work around this yesterday and while doing so, remembered this topic:

Greyscale palette is greatly reduced when resizing images

For grayscale (greyscale) JPEGs, Adjust Cover downsamples the image from 256 to 4 colors and outputs a non-greyscale JPEG. 8-bit grayscale images should maintain their colorspace during and after conversion. Example: Drag attached 1000px 8-bit (256-color) grayscale image into cover art box. Right-click and choose Adjust Cover. Resize to 600px, any quality. Observe unwanted color reduction. Right-click and save the reduced image to a new file. Observe (e.g. in Photoshop) that it's not a graysca…

I gave up on it the last time I've tried, but will give it another go over the coming days and will keep you posted.

[Florian]

I think I found a solution for this problem and have fixed it with Mp3tag v3.22e.

[JohnIV]

Looking good from my testing over the last few days, thanks Florian! (MP3s and WMAs).