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tl;dr By reading some Internet and by performing own experiments I've learnt that no matter what file type my images has, PowerPoint 365 always saves them internally as PNG. Making file for any presentation with many photos extremely huge.

Is there anything I can do about it, beside using brute-force methods, like the one described here?


I have a 100+ slides presentation that has pure-text only slides and occupies less than 1 MB on my disk. I have added one photographic background to it. Even though source file has 360 kB on disk (saved as JPEG), PowerPoint presentation's file size jumped to 5,5 MB after that. After examining file contents I quickly learned that for some reason PowerPoint has saved this very single image as a PNG.

Is there anything I can do to prevent such idiotic behavior? This is my beginning into making full-sized photo backgrounds in PowerPoint slides. But I already have presentations like 30+ slides which (after saving to disk) has 100+ MB of size. An I am completely unable to send them via Gmail.

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    Imported JPEG images should stay in this format, unless you have enabled compression or other image-modifying options when importing.
    – harrymc
    Jun 3 at 10:50
  • Yes, I am using heavily filters, crops, brightness and contrast modification after importing / adding images and placing then on given slide. Am I getting you correctly that in this case PowerPoint will save everything in PNG due to this, because it cannot apply any image filtering or processing over JPEGs saved internally?
    – trejder
    Jun 3 at 15:09
  • Yes, PowerPoint "compression" is atrocious. It's better to do these operations outside of it, just importing the result without modification.
    – harrymc
    Jun 3 at 15:17
  • Then I'd say that your comment / explanation directly answers the question (No, it is not possible due to how PowerPoint works). Care for crafting one, so I can accept it?
    – trejder
    Jun 3 at 15:25

1 Answer 1

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PowerPoint, when importing JPEG and PNG images, keeps them in their format inside the presentation.

Your images are getting larger because you are using PowerPoint to do image operations, as you say you are using "heavily filters, crops, brightness and contrast modification after importing".

PowerPoint is well-known for using an inefficient compression algorithm, so images that it operates upon become just too large.

It is better to avoid PowerPoint image-operations in the workflow. Do these operations using efficient tools, just importing the results. Use PowerPoint only for what it does best - creating presentations.

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  • IIRC, one reason images get so "plump" in this situation is because PPT maintains the modifications as layers so that a) you can remove/adjust the modifications if you need to and b) so that older versions that don't understand the adjustments can still just display the final result. Some of the adjustments require alpha transparency, which JPG doesn't support, so the image is converted to PNG. If you don't want to use an external app to do the adjustments, do so, then copy the end result, choose PasteSpecial | JPG then delete the original. Voila. Best of both worlds. Jun 4 at 16:29

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