XnView Software

... imagine if you have several files with several sizes (ex. 128x128, 256x256 and 512x512) and want to convert all of them in one step
A modification then, but I'm not sure that it quite meets your needs:

Image_2.png
In the second action 'Canvas resize' rescaling the width and the height ...

At a quick look I think so:

Image_1.png
lqFT3Tp-transformed.png
You had better check carefully.

Edit:

I don't know why there's a black line around the image -- it's not shown in the screenshot 'After' display?

So maybe almost, or can that be fixed??

Yes, that would work for this size ...

This is the original:

http://i.imgur.com/lqFT3Tp.png

and this is the result, width/height 75%/100%

http://i.imgur.com/nLrhAou.png

Both the original and the result have canvas size of 128x128 (with transparent background).

I've managed to accomplish similar effect, applying Resize, set to ...

Well, the only example that comes to me in mind is my recent work: resizing icons (pure png images) to look better on 4:3 resolutions, displayed on 16:9 display (the BIOS VESA resolution). For that purpose, the pictures should be "squashed" by their width and height with a percentage, calculated by ...

Is it possible to be resized an image (no matter the aspect ratio and the method) with keeping the original canvas size at the same time, much like the Transform option in Photoshop and other programs?