cffi-devel October 2013

cffi-devel@common-lisp.net

16 participants
34 discussions

[cff-devel] ….
by Marco Antoniotti 09 Oct '13

09 Oct '13

Hi apologies for the not-so-hidden-sarcasm. Subject says it all. As we know, the CLNET mail server is not Mailman, but could it be possible to customize the subject line in the "proper way"? There are tons of "old men tricks" out there that depend on certain Subject formatting conventions. cffi-devel is one of the best and more active fora in the CL community and I enjoy reading it… as long as it is nicely advertised in my mailbox :) All the best -- Marco Antoniotti

5 7

Need help accessing a nested struct member?
by Joeish W 07 Oct '13

07 Oct '13

I do apoligize if i added to much code on this....it just seems difficult to explain without showing all the code involve. pls let me know if this isnt worded right to community guidelines and i'll edit it....pls be precise so i know what to change.. here is how the struct CvSeq is defined #define CV_TREE_NODE_FIELDS(node_type) \ int flags; /* Miscellaneous flags. */ \ int header_size; /* Size of sequence header. */ \ struct node_type* h_prev; /* Previous sequence. */ \ struct node_type* h_next; /* Next sequence. */ \ struct node_type* v_prev; /* 2nd previous sequence. */ \ struct node_type* v_next /* 2nd next sequence. */ /* Read/Write sequence. Elements can be dynamically inserted to or deleted from the sequence. */ #define CV_SEQUENCE_FIELDS() \ CV_TREE_NODE_FIELDS(CvSeq); \ int total; /* Total number of elements. */ \ int elem_size; /* Size of sequence element in bytes. */ \ schar* block_max; /* Maximal bound of the last block. */ \ schar* ptr; /* Current write pointer. */ \ int delta_elems; /* Grow seq this many at a time. */ \ CvMemStorage* storage; /* Where the seq is stored. */ \ CvSeqBlock* free_blocks; /* Free blocks list. */ \ CvSeqBlock* first; /* Pointer to the first sequence block. */ typedef struct CvSeq { CV_SEQUENCE_FIELDS() } CvSeq; and here is how i ended up wrapping it. ;; (cffi:foreign-type-size '(:struct cv-seq)) = 96 (cffi:defcstruct cv-seq (flags :int) (header-size :int) (h-prev :pointer) (h-next :pointer) (v-prev :pointer) (v-next :pointer) (total :int) (elem-size :int) (block-max :pointer) (ptr :pointer) (delta-elems :int) (storage :pointer) (free-blocks :pointer) (first :pointer)) I was curious what to do with the h_next h_prev and v_prev and v_next, they seem to be recursive and they are not working or i am not using them right normally when a struct contains a member like CvMemStorage* storage; I wrap it like this (:pointer (:struct cv-mem-storage)) and it works but h_next i/e seems to point back to itself this is the way the h_next struct member works in c. in the below code while contours is not null it iterates though a while loop and through every iteration it sets the variable contours to the next pointer stored in h_next which is set by the cvFindContours function. the cvFindContours fubction in c adds a pointer to the h_next member of the CvSeq struct for every item in the picture it finds...pls see below link for more details and example picture (trying 2 keep this short) ... the code i got the below snippet from is the first program on this page.....http://opencv-srf.blogspot.com/2011/09/object-detection-tracking-u… (i broke it down so it would be easier to understand) int main() { IplImage* img = cvLoadImage("/home/w/quicklisp/dists/quicklisp/software/cl-opencv-master/images/FindingContours.png"); //converting the original image into grayscale IplImage* imgGrayScale = cvCreateImage(cvGetSize(img), 8, 1); CvMemStorage *storage = cvCreateMemStorage(0); //storage area for all contours CvSeq* contours= cvCreateSeq(CV_SEQ_ELTYPE_POINT, sizeof(CvSeq), sizeof(CvPoint), storage); //finding all contours in the image cvFindContours(imgGrayScale, storage, &contours, sizeof(CvContour), CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0)); //iterating through each contour while(contours) {cout << "contours = " << endl << " " << contours << endl << endl; //obtain a sequence of points of contour, pointed by the variable 'contour' contours = contours->h_next; } cout << "contours end = " << endl << " " << contours << endl << endl; return 0; } when i convert to lisp(below ...i didnt add while loop because h-next is null), i use nested with-foreign-slots to access the h-next member for debugging. it is a null pointer where in the c code above the h_next member is full of data...the function does work though....it works as good as it does in c (let* ((img (load-image "/home/w/quicklisp/dists/quicklisp/software/cl-opencv-master/images/FindingContours.png" 1)) (img-size (get-size img)) (img-grayscale (create-image img-size +ipl-depth-8u+ 1)) (storage (create-mem-storage 0)) ( contours (create-seq +seq-eltype-point+ (cffi:foreign-type-size '(:struct cv-seq)) (cffi:foreign-type-size '(:struct cv-point)) storage))) (find-contours img-grayscale storage contours (cffi:foreign-type-size '(:struct cv-contour)) +retr-list+ +chain-approx-simple+ (make-cv-point :x 0 :y 0)) (cffi:with-foreign-slots ((h-next) contours (:struct cv-seq)) (cffi:with-foreign-slots ((h-next) h-next (:struct cv-seq)) h-next) )) just outputs a null-pointer>> #.(SB-SYS:INT-SAP #X00000000) any help on this would be appreciated?

1 0

Fwd: Could use help wrapping opencv function?
by Attila Lendvai 07 Oct '13

07 Oct '13

[this time to the list also] > CV_INLINE CvPoint cvPoint( int x, int y ) > { > CvPoint p; > > p.x = x; > p.y = y; > > return p; > } it's been a while since i was fooling around with C... but 'p' is a local variable on the stack, and if you return its address, then it will point into nowhere when the C function's stack frame is unwound. for that code you should receive a scary warning from any sane C compiler. and a bit of meta re your emails... read this: http://www.catb.org/esr/faqs/smart-questions.html -- • attila lendvai • PGP: 963F 5D5F 45C7 DFCD 0A39 -- “Most people think they need a ruler. Perhaps we should give them a fake one that doesn't actually do anything, and then they won't think about it. It is sort of like giving an infant a pacifier.” — Perry Metzger

2 1

Could use help wrapping opencv function?
by Joeish W 05 Oct '13

05 Oct '13

the function I'm trying to wrap is here CV_INLINE CvPoint cvPoint( int x, int y ) { CvPoint p; p.x = x; p.y = y; return p; } and here is the related struct typedef struct CvPoint { int x; int y; } CvPoint; I wrap it like this like I normally do ; this is how swig wrapped the defcstruct (cffi:defcstruct cv-point (x :int) (y :int)) ;; CvPoint cvPoint(int x, int y) (cffi:defcfun ("cvPoint" pointy) (:struct cv-point) "constructs CvPoint structure." (x :int) (y :int)) the wrapper i made runs at the repl but when i call the function i get error CL-OPENCV> (point 7 7) The value NIL is not of type SB-SYS:SYSTEM-AREA-POINTER. [Condition of type TYPE-ERROR] Backtrace: 0: (CFFI::CALL #.(SB-SYS:INT-SAP #X7FFFE0000E10) NIL #.(SB-SYS:INT-SAP #X7FFFE5427FD0) #.(SB-SYS:INT-SAP #X7FFFE5427FD8)) Locals: SB-DEBUG::ARG-0 = #.(SB-SYS:INT-SAP #X7FFFE0000E10) SB-DEBUG::ARG-1 = NIL SB-DEBUG::ARG-2 = #.(SB-SYS:INT-SAP #X7FFFE5427FD0) SB-DEBUG::ARG-3 = #.(SB-SYS:INT-SAP #X7FFFE5427FD8) in the backtrace it appears to be linking 4 parameters and i think its because of this CV_INLINE CvPoint cvPoint( int x, int y ) { CvPoint p; p.x = x; p.y = y; return p; } because their are 4 items in the CV_INLINE I was hoping someone could help me get by this error message

1 0

How do I approxmate C pointer dereferencing?
by Joeish W 05 Oct '13

05 Oct '13

in my library ive already written wrappers for these opencv functions create-camera-capture query-frame img-size create-image the struct related to create-image is IplImage and i have it defined like this ;; ;(cffi:foreign-type-size '(:struct ipl-image)) = 144 (cffi:defcstruct ipl-image (n-size :int) (id :int) (n-channels :int) (alpha-channel :int) (depth :int) (color-model :int) ;;Ignored by OpenCV - was :pointer, changed to :int so the struct values would match OpenCV's (channel-seq :int) ;;Ignored by OpenCV - was :pointer, changed to :int so the struct values would match OpenCV's (data-order :int) (origin :int) (align :int) (width :int) (height :int) (roi (:pointer (:struct ipl-roi))) (mask-roi :pointer) (image-id :pointer) (tile-info :pointer) (image-size :int) (image-data :string) (width-step :int) (border-mode :pointer) (border-const :pointer) (image-data-origin :string)) so when i call the above functions and then print the struct values with the below code it looks like this CL-OPENCV> (defparameter capture (create-camera-capture 0)) (defparameter frame (query-frame capture)) (defparameter img-size (get-size frame)) (defparameter img (create-image img-size +ipl-depth-8u+ 3)) IMG CL-OPENCV> (cffi:with-foreign-slots ((n-size id n-channels alpha-channel depth color-model channel-seq data-order origin align width height roi mask-roi image-id tile-info image-size image-data width-step border-mode border-const image-data-origin) img (:struct ipl-image)) (format t "n-size = ~a~%id = ~a~%n-channels = ~a~%alpha-channel = ~a~%depth = ~a~%color-model = ~a~%channel-seq = ~a~%data-order = ~a~%origin = ~a~%align = ~a~%width = ~a~%height = ~a~%roi = ~a~%mask-roi = ~a~%image-id = ~a~%tile-info = ~a~%image-size = ~a~%image-data = ~a~%width-step = ~a~%border-mode = ~a~%border-const = ~a~%image-data-origin = ~a~%" n-size id n-channels alpha-channel depth color-model channel-seq data-order origin align width height roi mask-rOI image-id tile-info image-size image-data width-step border-mode border-const image-data-origin)) n-size = 144 id = 0 n-channels = 3 alpha-channel = 0 depth = 8 color-model = 4343634 channel-seq = 5392194 data-order = 0 origin = 0 align = 4 width = 640 height = 480 roi = #.(SB-SYS:INT-SAP #X00000000) mask-roi = #.(SB-SYS:INT-SAP #X00000000) image-id = #.(SB-SYS:INT-SAP #X00000000) tile-info = #.(SB-SYS:INT-SAP #X00000000) image-size = 921600 image-data = width-step = 1920 border-mode = #.(SB-SYS:INT-SAP #X00000000) border-const = #.(SB-SYS:INT-SAP #X00000000) image-data-origin = NIL NIL I'd rather not have to call the with-foreign-slots function with all that code every time id like to access slot values id rather do exactly like in c and call img->depth for example to access the IplImage struct member depth....Is there a way i can have this exact functionality in lisp with the above struct or any other....if i did have to call (img depth) i guess that would be ok but id rather create some sort of dereferencing operator equivelant to do this as easy as in c....either way can someone show me how to dereference pointers in the tiniest way possible like in c

1 0

test 5 pls disregard
by Joeish W 05 Oct '13

05 Oct '13

(defun create-trackbar-example (&optional (camera-index 0) (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 (cffi:foreign-alloc :int :initial-contents '(50)))) (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* ((frame (query-frame capture) (query-frame capture)) (dest (clone-image frame)) (scalar 0)) ((plusp (wait-key *millis-per-frame*)) nil) (format t "Trackbar level: ~a~%~%" (cffi:mem-ref contrast :int)) (create-trackbar "Brightness" window-name contrast 100 (change-contrast contrast window-name frame dest)) (setf scalar (scalar (- (cffi:mem-ref contrast :int 50)) (- (cffi:mem-ref contrast :int) 50) (- (cffi:mem-ref contrast :int) 50))) (add-s frame scalar dest) (show-image window-name dest)) (destroy-window window-name)))) (defun create-trackbar-example (&optional (camera-index 0) (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 (cffi:foreign-alloc :int :initial-contents '(50)))) (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* ((frame (query-frame capture) (query-frame capture)) (dest (clone-image frame)) (scalar 0)) ((plusp (wait-key *millis-per-frame*)) nil) (format t "Trackbar level: ~a~%~%" (cffi:mem-ref contrast :int)) (create-trackbar "Brightness" window-name contrast 100 (change-contrast contrast window-name frame dest)) (setf scalar (scalar (- (cffi:mem-ref contrast :int 50)) (- (cffi:mem-ref contrast :int) 50) (- (cffi:mem-ref contrast :int) 50))) (add-s frame scalar dest) (show-image window-name dest)) (destroy-window window-name)))) (defun create-trackbar-example (&optional (camera-index 0) (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 (cffi:foreign-alloc :int :initial-contents '(50)))) (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* ((frame (query-frame capture) (query-frame capture)) (dest (clone-image frame)) (scalar 0)) ((plusp (wait-key *millis-per-frame*)) nil) (format t "Trackbar level: ~a~%~%" (cffi:mem-ref contrast :int)) (create-trackbar "Brightness" window-name contrast 100 (change-contrast contrast window-name frame dest)) (setf scalar (scalar (- (cffi:mem-ref contrast :int 50)) (- (cffi:mem-ref contrast :int) 50) (- (cffi:mem-ref contrast :int) 50))) (add-s frame scalar dest) (show-image window-name dest)) (destroy-window window-name)))) (defun create-trackbar-example (&optional (camera-index 0) (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 (cffi:foreign-alloc :int :initial-contents '(50)))) (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* ((frame (query-frame capture) (query-frame capture)) (dest (clone-image frame)) (scalar 0)) ((plusp (wait-key *millis-per-frame*)) nil) (format t "Trackbar level: ~a~%~%" (cffi:mem-ref contrast :int)) (create-trackbar "Brightness" window-name contrast 100 (change-contrast contrast window-name frame dest)) (setf scalar (scalar (- (cffi:mem-ref contrast :int 50)) (- (cffi:mem-ref contrast :int) 50) (- (cffi:mem-ref contrast :int) 50))) (add-s frame scalar dest) (show-image window-name dest)) (destroy-window window-name))))

1 0

test 4 pls disregarde
by Joeish W 05 Oct '13

05 Oct '13

<code>(cffi:defcstruct (cv-size :classcv-size-type)(width :int)(height :int))(defmethod cffi:translate-from-foreign (p (type cv-size-type))(let((plist (call-next-method)))(make-size :width (getf plist 'width) :height (getf plist 'height))))</code> and my opencv wrappers for CvGetSize and cvCreateImage, get-size and create-image, are defined like this ;;CvSizecvGetSize(constCvArr*arr)(cffi:defcfun ("cvGetSize"get-size)(:structcv-size)(arr cv-arr));;IplImage*cvCreateImage(CvSizesize,intdepth,intchannels)(cffi:defcfun ("cvCreateImage"%create-image)ipl-image (size :int64)(depth :int)(channels :int))(defun create-image (size depth channels)"Create an image with dimensions given by SIZE, DEPTH bits per channel, and CHANNELS number of channels."(let((nsize (size->int64 size)))(%create-image nsize depth channels))) here is the definition of size->int64 (DEFUN SIZE->INT64 (S)(+(SIZE-WIDTH S)(ASH (SIZE-HEIGHT S)32)))it converts get-size output which isa structure here:#S(SIZE :WIDTH 640 :HEIGHT 480)into64-bit integer,which CFFI can handle but i love the idea of the translate-foreign defmethod's so i was wondering if you can show my how to make the translate-into-foreign version of the below from method this would really make my library awesome (defmethod cffi:translate-from-foreign (p (type cv-size-type))(let((plist (call-next-method)))(make-size :width (getf plist 'width) :height (getf plist 'height))))

1 0

could i get help with code formatting
by Joeish W 05 Oct '13

05 Oct '13

as you can see my last attempts were unsuccessful I indented my code as i normally do when i add to a site but it didnt work how does everyone else add code so neatly

1 0

test 3 pls disregard
by Joeish W 05 Oct '13

05 Oct '13

CL-OPENCV>;;(cffi:foreign-type-size '(:struct cv-size)) = 8 (cffi:defcstruct (cv-size :class cv-size-type) (width :int) (height :int)) (defmethod cffi:translate-from-foreign (p (type cv-size-type)) (let ((plist (call-next-method))) (make-size :width (getf plist 'width):height (getf plist 'height)))) (defmethod cffi:translate-to-foreign (value (type cv-size-type)) (let ((plist ())) (setf (getf plist 'width)(size-width value)(getf plist 'height) (size-height value)) (call-next-method plist type))) ;; CvSize cvGetSize(const CvArr* arr) (cffi:defcfun ("cvGetSize" get-size) (:struct cv-size) (arr (:pointer cv-arr))) ;; IplImage* cvCreateImage(CvSize size, int depth, int channels) (cffi:defcfun ("cvCreateImage" create-image) (:pointer (:struct ipl-image)) (size (:struct cv-size)) (depth :int) (channels :int)) STYLE-WARNING: redefining CL-OPENCV:GET-SIZE in DEFUN STYLE-WARNING: redefining CL-OPENCV:CREATE-IMAGE in DEFUN CREATE-IMAGE CL-OPENCV> (defparameter capture (create-camera-capture 0)) (defparameter frame (query-frame capture)) (defparameter img-size (get-size frame)) (defparameter img (create-image img-size +ipl-depth-8u+ 3))

1 0

test 2 pls disregard
by Joeish W 05 Oct '13

05 Oct '13

(cffi:defcstruct (cv-size :classcv-size-type)(width :int)(height :int))(defmethod cffi:translate-from-foreign (p (type cv-size-type))(let((plist (call-next-method)))(make-size :width (getf plist 'width) :height (getf plist 'height)))) and my opencv wrappers for CvGetSize and cvCreateImage, get-size and create-image, are defined like this ;;CvSizecvGetSize(constCvArr*arr)(cffi:defcfun ("cvGetSize"get-size)(:structcv-size)(arr cv-arr));;IplImage*cvCreateImage(CvSizesize,intdepth,intchannels)(cffi:defcfun ("cvCreateImage"%create-image)ipl-image (size :int64)(depth :int)(channels :int))(defun create-image (size depth channels)"Create an image with dimensions given by SIZE, DEPTH bits per channel, and CHANNELS number of channels."(let((nsize (size->int64 size)))(%create-image nsize depth channels))) here is the definition of size->int64 (DEFUN SIZE->INT64 (S)(+(SIZE-WIDTH S)(ASH (SIZE-HEIGHT S)32)))it converts get-size output which isa structure here:#S(SIZE :WIDTH 640 :HEIGHT 480)into64-bit integer,which CFFI can handle but i love the idea of the translate-foreign defmethod's so i was wondering if you can show my how to make the translate-into-foreign version of the below from method this would really make my library awesome (defmethod cffi:translate-from-foreign (p (type cv-size-type))(let((plist (call-next-method)))(make-size :width (getf plist 'width) :height (getf plist 'height)))) I was going to try stuff and add it but for the get-size output structure, it isnt a plist so not really sure what to put there for the (let((plist (call-next-method))) part, for the (make-size :width (getf plist 'width) :height (getf plist 'height))))

1 0

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cffi-devel October 2013