To resize many image files to a common size, use the batch processing tools in the free XnView image viewer. XnView MP offers robust image editing for computers under Windows control , Mac and linux .
The instructions we detail below are for XnView MP version 0.93.1
How to batch resize an image in XnView MP
The conversion process is carried out using the utility wizard:
Select Tools > batch conversion.
When the batch conversion tool launches, click the button Add files to add images.
Go to tab Actions utilities. Click » Add Action», then select the action you want to take. You will see one of your images as a preview in the right pane. To resize, click Add action > Image > Resize .
Set options for the conversion wizard. Use the drop-down list to automatically configure settings, or configure them manually. In most cases, the preset will work, but you can further adjust the height and width of the image and select fit and shrink limits.
Go to tab » Conclusion » and set the desired output rules.
You can set the output folder, file name template, image metadata settings, and actions to take after the export is complete.
Click convert, to start the package.