Fw: [cffi-devel] How would i use a function with a callback parameter

[Joeish W]

On , Joeish W <joeish80829 at yahoo.com> wrote:
 

>
>I got the callback working somewhat to illustrate here is my code so far below and again im attempting to convert the lowest function on this page: http://opencv-srf.blogspot.com/2011/11/track-bars.html
>
>(defcallback a :void  ((contrast :int) (img cv-arr) (dest cv-arr))
> (format t "img-1: ~a~%~%" img)
>(format t "dest-1: ~a~%~%" dest)
>(format t "Trackbar level-1: ~a~%~%" contrast))
>
>
>
>(defun create-trackbar-example (&optional (camera-index *camera-index*) (width *default-width*)
>                (height *default-height*))
>  "Creates a trackbar and attaches it to the specified window.
>   Move the
 slider to adjust the brightess of the camera output"
>  (with-capture (capture (create-camera-capture camera-index))
>    (let ((window-name "CREATE-TRACKBAR Example")
>      (contrast (foreign-alloc :int :initial-contents '(10)))
>      (dest (create-image (size width height) +ipl-depth-8u+ 3)))
>      (set-capture-property capture +cap-prop-frame-width+ width)
>      (set-capture-property capture +cap-prop-frame-height+ height)
>      (named-window window-name)
>      (move-window window-name 600 175)
>      (do* ((img (query-frame capture) (query-frame capture))
>            (img (clone-image img))
>            (scale
 0)
>            (n 0))
>       ((plusp (wait-key *millis-per-frame*)) nil)
>    (create-trackbar "Contrast" window-name contrast 21 (callback a))
>    (format t "img-2: ~a~%~%" img)
>    (format t "dest-2: ~a~%~%" dest)
>    (format t "Trackbar level-2: ~a~%~%" (mem-ref contrast :int))
>    (show-image window-name img))
>      (release-image dest)
>      (destroy-window window-name))))
>
>
>im testing the callback function and it works, it is called when the trackbar is moved, i know this  because the Trackbar level-2 format output from the callback function prints which it should and the output  of the contrast variable in that format function also changes.....the contrast variable is changed in the
 create-trackbar-example function and the callback function picks up that variable with the (contrast :int) parameter...  my new question is how do i get the callback function to pick up the img and dest variables from the create-trackbar-example function....when the code runs the output of the format t functions from the call back with the img and dest variables in them are different from the output of the format t functions from the create-trackbar-example  with the img and dest in them which means the callback isnt picking those up but it is picking up the variable contrast...and oddly enough i dont have to mem-ref the contrast variable in the callback function....when i just evaluate the variable contrast it prints a number....I think the parameters of the callback are defined righ,t the img and dest are defined as cv-arr (a defctype :pointer) in my library
>...any help is appreciated
>
>On Sunday, October 27, 2013 12:03 AM, "f9cef2aa at yandex.ru" <f9cef2aa at yandex.ru> wrote:
> 
>>here is my attempt but i have no idea how to define a function as a pointer and ive tried alot of  variations but is too long to post.  The defun change contrast compiles btw...i tried using make-pointer to make the change-contrast function a pointer but make-pointer wants it to be a real...so cant use foreign-alloc i dont think because the function needs to be converted to a pointer first to use that...any guidance is appreciated
>>>
>>>(defun change-contrast (&optional contrast img dest)
>>>(if (< contrast 10) (scale img dest (/ 1 (coerce (- 11 contrast) 'double-float)))
>>>    (if (>= contrast 10) (scale img dest (- contrast 9))))
>>>     (show-image "MyImage" dest))
>>>
>>>(defun display (filename)
>>>  "Open the image FILENAME and show it in a window."
>>>  (let* ((img (load-image filename 1))
>>>        (img-size (get-size img))
>>>       (dest (create-image img-size +ipl-depth-8u+ 3))
>>>       (contrast (cffi:foreign-alloc :int :initial-contents '(10))
>>>      (test "not sure what to do here"))) 
>>>    (named-window "MyWindow" 1)
>>>   (create-trackbar "conrast" "MyWindow" contrast 21 test)
>>> (princ (mem-ref contrast :int))
>>>  (change-contrast (mem-ref contrast :int) img dest)
>>>    (loop while (not (= (wait-key 0) 27)))
>>>    (release-image img)
>>>    (release-image dest)
>>>    (destroy-window "MyWindow")))
>>
>>Have you read defcallback documentation? If no, read it and try to use
>>defcallback. If yes, what was your problem when using defcallback?
>>
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