Compress image option is greyed out in Calc?

I have a spreadsheet that I moved from Excel to Libre Office Calc specifically to be able to compress images in it. For all the images that were already in it, I was able to right click on them and compress them, all fine so far.

However now, if I paste a new image in from the clipboard, there is no option to compress it if I right click on it, and if I use the main menu option Format → Image → , the Compress option is greyed out.

After pasting the image in, the Edit menu shows "Undo: Insert Metafile ‘Image1’ ", if that helps in knowing why the Compress option isn’t available.

If you paste an image then it is pasted as png. If you insert image then it can be one of the acceptable image formats such as jpg which can be compressed further, albeit witha loss of detail.

A png image does not lose information it its compression so will not normally be compressed more. A jpg is a lossy format so you can compress it further by throwing away some more detail. If you remove information from a png, e.g. by saving a colour picture in 256 colours instead of 16,7M colours it can be made smaller, or even smaller as greyscale, but you would do that in an image editor prior to inserting. PNGs can look cleaner and sharper for images that don’t need a lot of different colours (charts, drawings, screenshots, etc.) compared to jpgs which can look fuzzy around the edges as compression increases.