Fixing up images in a powerpoint presentation

Ideally you would fix up images before you add them to powerpoint, but what if you have just made a complex powerpoint presentation and realised, for example, that the images all have an undesirable colour cast. And perhaps you have many images in the file with the same issue. Fixing them one by one by adjusting the original and replacing the images in the ppt is tedious. Fortunately, with PPTX files there is an easier approach.

The PPTX file is actually a zipped archive of the files and instructions to compile your presentation. So:

1. make a copy of the file to work with, perhaps in a separate folder to avoid any confusion
2. change the extension from .PPTX to .ZIP
3. use a program such as 7-zip to extract the zipped file to a new folder.
4. browse the extracted files. You should find a folder called ppt. Open this and locate the subfolder media. Inside this should be all the image files you added to your document.
5. Adjust the images as needed. In my case, I copied all the media files to a separate folder outside the extracted archive. I loaded images into Adobe Lightroom, adjusted one image, then told lightroom to apply these changes to all the relevant images. That way all the images got exactly the same adjustment. But with programs like Lightroom even adjusting all the images separately is not too time consuming. If you don’t have Lightroom, free, open-source programs like Darktable and RawTherapee also allow batch editing.
6. I then exported the adjusted images back to the original media folder (overwrite the old ones). In LR make sure you are outputting to the same image format and not resizing. I haven’t experimented to see what happens if the images are different image formats or resized, but I suspect something may break,
7. Select all the files and folders in the top level of the archive, and re-combine them into a zip archive. If you are using a program like 7-zip, you can even tell it to save the zip file with a pptx extension.
8. Now check the file by opening it. Hopefully PPT will open the file and you will see the edited images in place, and all the layout, text etc should be placed as it was in the file you started with.

Below is an example of the top corner of one slide. The whole presentation has 104 images spread over 10 slides, but I only needed to edit a couple and then copy the edits to the remaining images of the same type so the whole process was very much faster than individually editing each image.