When previews are enabled, the Special menu lets you copy pictures to the Clipboard so that you can quickly attach them to an email message or paste them into a document.
Select the picture in the Special menu, display the Copy submenu, and choose a size from the Image submenu.
You can choose between five image sizes: Actual Size, Large (1280 x 960 pixels for a 4 x 3 size ratio picture), Medium (640 x 480 pixels), Small (320 x 240 pixels), and, for pictures in the Aperture or iPhoto library, Thumbnail.
If you need to rotate the picture before copying it to the Clipboard, hold down the Control (clockwise rotation) or Option (counter clockwise rotation) key while choosing the image size.
If you want to attach a picture to a Mail message or paste it into a Pages or Keynote document, you can copy the image file by choosing File from the Copy submenu.