An External Image is an intermediate object. It is a representation of a graphic but is not associated with a port and cannot be used directly for drawing.
An object of type
external-image
is created by reading an image from a file, or by externalizing an
image
object, or by copying an existing
external-image
. Or, if you have the image bitmap data, you can create one directly as in the
examples/capi/buttons/button.lisp
example.
The
external-image
contains the bitmap data, potentially compressed. You can copy
external-image
objects, or write them to file, or compress the data.
You cannot query the size of the image in an
external-image
object directly. To get the dimensions without actually drawing it on screen see Pixmap graphics ports.
If you create an
image
and want to externalize it to write it to file, follow this example:
(let ((image (gp:make-image-from-port pane 10 10 200 200)))
(unwind-protect
(gp:externalize-and-write-image pane image filename )
(gp:free-image pane image)))
CAPI User Guide (Windows version) - 30 Aug 2011