The http-image package is a process-driven image downloader and CAPI output-pane that can render downloaded images.
It uses of my http package to download the image, which is also freely available.
The http-image system is divided into two parts:
- Functions for downloading images in background processes.
- An
output-panesubclass for rendering images.
To download an image, simply call http-image-download with a URL and a callback function. The signature of the callback function should be:
(external-image &optional error)
If external-image is nil then error will have the condition that was caught. Otherwise, external-image can be used per the LispWorks documentation.
(http-image-download url callback &key reload (timeout 30)) => process
If reload is T then the image will be forced to download. Otherwise, if the image has been downloaded once already, the previous (cached) version will be returned.
The entire download cache can be cleared at any time with http-image-cache-clear. This can be quite useful for debugging, but would rarely be called in production use.
Wrapping the http-image-download function for you is the http-image-pane. Simply create one with a URL:
CL-USER > (capi:contain (make-instance 'http-image-pane :url "http://www.lisperati.com/lisplogo_fancy_256.png"))
At this point a window should appear and a background process is spun up to download the image in the background. Once loaded, it should appear. The pane should be resizeable and the image should resize to fit, maintaining its original aspect ratio.
Since http-image-pane is just a subclass of output-pane, all the other :default-initargs like :background and :input-model can be used to manipulate the pane.
Note: The :create-callback, :destroy-callback, and :display-callback options are used by the http-image-pane. Take care if you wish to do something different!
If you want to change the URL being pointed to, simply use #'(setf http-image-pane-url) with a new URL. And if you want to download the current image again, use http-image-pane-refresh.
CL-USER > (setf (http-image-pane-url *) "http://www.lisperati.com/lisplogo_flag2_256.png")