This mini-tutorial may be useful for those working in museums and archives, or doing print work with big maps, who encounter image files so huge they can’t be opened.

Problem: You have been sent a huge image file, and you need to shrink and resize it. It’s very nice that the sendee only sent a 80Mb .JPG rather than their 8Gb original map sheet. But even their 28,000 pixel .JPG can’t be opened on your puny PC. Even Photoshop and IrfanView balk at loading/viewing it. You can’t use the free GigaPXTools (for re-sizing gigapixel images without opening them) because… it prefers .TIFs and can’t work with .JPG files.

Solution: the free IrafanView can shrink it, if used in batch mode.

Method: First close down everything on your PC that’s not essential and might be eating your PC’s memory. Make sure you have the latest 64-bit IrfanView.

1. Then place your target image, on its own, in a new folder called ‘batch’.

2. Open any small image in IrfanView, to launch the software.

3. Press ‘B’ to open Batch conversion. In “Look in:” navigate to your target folder. You may have to do this a few times until your target image appears as a preview thumbnail. Do not click on the preview thumbnail (as this will almost certainly crash IrfanView)! This step will at least show you that file is viable as an image, and not corrupted.

Now you can see why we needed the image on its own in its own folder — IrfanView has enough to do with just showing a preview of this file, let alone previewing any other images in the same folder at the same time. If even this step proves too much for IrfanView, try switching to file-name view only, and then re-starting the process.

4. Then tick “Use Advanced Options” and set “Resize” to 3000 pixels, or whatever reduced size you want. Click OK.

5. Set your target output folder. Without clicking on the Preview thumbnail, click the “Add All” button to add the target file to the list of files to be processed.

6. Click “Start Batch”. Then you go off and have a coffee, as it’s likely to take 20 minutes. A Windows message that the software is “Not responding” is normal. Eventually there will be a message from IrfanView that the batch process has completed.