This example shows a batch of 3 files being re-sized to max. dimension 800px

It is self explanatory.

The resizer is opened
The maximum dimension is changed from 640 to 800px - the last size used is always remembered.
Three images on the Desktop  are selected and dragged onto the resizer
The files are automatically processed and the new files appear on the Desktop - same name prefixed with
The resizer is closed
The files are selected and previewed.
The size can be set to anything  you like, so if you want to make thumbnails, set it to say 100.

Works with png files or jpg images.

Remember the new file will always be in the same directory (in the demo it's the Desktop) as the original and the original is unchanged.

Could not be easier. Best view this video full screen.

You can download resizer2 here

No install required, it runs straight off