Image degradation when making images smaller and using Save as Picture

PowerPoint is not a great tool for graphic design. If you are sizing a pasted image, you are going to lose resolution. Typically a graphics designer will use vector graphics to design logos so the resolution is preserved in size changes. When you paste an image into PowerPoint you are dealing with a raster image--you cannot shrink it without losing resolution, and you cannot increase the size without getting pixilation.

I think PowerPoint uses vector graphics so you may get better results by making a copy of the original graphic within PowerPoint, then sizing the copy, then saving it. That way you are doing the sizing as early in the process as possible. I am just guessing without knowing how you created your image. If it is not proprietary maybe you can share the PowerPoint file here for more help.

By the way, resolution is unrelated to compression. Compression is the process by which image information is recoded to result in a smaller file size. This is similar to zipping a text file. There are two types of compression: Lossless and lossy. Lossless compression stores the image in a smaller size without losing any information; PNG is lossless. Lossy compression removes some information but image degradation is minimal; JPEG is lossy. You can have a high-res image that is stored with lossy compression, and low-res image that is stored with lossless compression.

Yes I would try that but if it has text, you are probably going to have to resize the text size separately as it will stay the same if you scale down the graphic elements. That is, if your image contains Arial 10-point text and you shrink your image to 50%, it will still be 10-point text and you will have to size it down to 5 points.