Have you tried to use the report feature of Qlikview? You can add a button to your sheet to print report and scale the report to the size you'd like. However, this will print the sheet to a pdf. The PDF will give you more options to crop and edit, if you have adobe acrobat.
Reports > Edit Reports > Add Report then move the report screen down some and control + A on your dashboard then drag and drop the whole thing into the report and size appropriately. Add a button with the action to print report with the correct report ID.
Edit: You could also change the action of the button to print sheet without creating a report, but the report will give you more options.
Thank you very much for your quick reply, but: yes, I know this "solution" as well, but it is not what I want. What I want is to have "the right image" available on the clipboard in order to be able to paste it whereever I like - without any workaround.