Every now and again, Microsoft Powerpoint or Excel graphs or illustrations turn out just as you want them. In these situations, it’s handy to have a way of saving each slide as a high-quality image file. I’ve used the one-off registry tweak described below to successfully generate figures for journal articles from Powerpoint slides.
I used to do this by starting the Powerpoint show in fullscreen (having pasted the Excel graph into a slide, if necessary) and pressing Print-Screen (PrtScn) and pasting the screen-grab-quality image into GIMP to edit and save. This is perfect if the image you need only needs to be high enough quality to display on screen e.g. if you’re making instruction screens for experiments and don’t fancy messing about with coding each block of text for the instructions in E-Prime, Superlab, Matlab etc. However, if you need to produce files that you can submit to journals as figures, then you need something that’s much higher quality (usually journals will stipulate a minimum resolution of 300dpi).
The standard “Save As” .bmp, .tif, .jpg options in Powerpoint will produce some decidedly jagged, 96dpi images, which aren’t much good for anything other than making thumbnails of your slides. However, these is a tweak in the form of a Microsoft-suggested registry edit that fixes this and allows you to saves images with resolutions in excess of 300dpi.
If you follow the instructions, you’ll be able to set resolutions of up to 307dpi in Powerpoint 2003.
The images you see here are examples created from a 1″ x 1″ Powerpoint slide that I have enlarged (96dpi) and shrunk (307dpi) so they are comparable on the same scale. You can see the fuzziness of the Powerpoint default output image on the left compared to the one on the product of the registry-tweaked image on the right.
WARNING: Don’t try and set the resolution to be any higher than 307dpi (on Powerpoint 2003) though, as if you do so and manage to avoid causing a crash every time you try and save presentations, on large images you’ll end up with images where the bottom-half looks like it has been squished up, leaving the text isolated – worse than standard 96dpi images as far as reader-comprehension goes!