Copy an image to the clipboard.
Launch the Preview app.
Choose New from Clipboard from the File menu.
When the image window opens, click on the toolbox icon to enable the editing features. Screen shot.
You should see a row of icons.
Resize an image, usually scaling.
Make the background transparent.
Draw an arrow on the image.
Save as either GIF, JPG or PNG.
The Preview app can do all this and more. And the other features don't seem to get in the way.
I'm still figuring out how to fit it into my workflow.