Go back to copying images with setImageData

Go back to copying images with setImageData

A previous change was made based on a wrong assumption that you could only copy one format of image data and that the program doing the copying decides the format that gets pasted.

The truth is that the app doing the copying gets to decide which formats are sent to the clipboard and can send multiple types of data, but not which format gets pasted. Only the app receiving the paste gets to decide which format gets pasted. If it doesn't support the copied format, nothing will be pasted. Because of this, images should be copied as uncompressed images. If you want to paste a JPEG into Firefox/Chromium/Electron apps directly, you can't really do that. You have to save a JPEG file and then copy the file as a file URL. I'd like to do that instead so that the copied image can always be compressed in the preferred format, but Flatpak apps currently can't use /tmp without the user adding explicit permission specifically for /tmp.

Another issue with trying to copy images directly in the preferred format is that lossy compressed formats like JPEG will be decompressed when Spectacle closes, expanding 2-8x their compressed size. This is likely an issue with Klipper (probably HistoryImageItem) and maybe KSystemClipboard.

BUG: 485096 CCBUG: 465781 CCBUG: 465972

Set suggested filename for copied images

Gives a useful default filename when pasting.