Units

First, use the following two units in your application (note that both units must be used):

Printing a bitmap

To call the preview form for a bitmap, use the BitmapPrint function:

function BitmapPrint(
  ABitmap: TBitmap;
  var AOptions: TATPrintOptions): Boolean;

Parameters:
ABitmap: Bitmap to print.
AOptions: Printing options.

Result:
True if printing was completed, False if printing was cancelled or some errors occured.

Printing an image

To call the preview form for an image (TImage), use the ImagePrint function:
function ImagePrint(
  AImage: TImage;
  var AOptions: TATPrintOptions): Boolean;

Parameters:
AImage: Image object to print. All image types can be printed: bitmaps, metafiles, icons etc.
AOptions: Printing options.

Result:
The same as for the BitmapPrint function.