// JCL_DEBUG_EXPERT_GENERATEJDBG OFF
// JCL_DEBUG_EXPERT_INSERTJDBG OFF
// JCL_DEBUG_EXPERT_DELETEMAPFILE OFF
program VideoProcessing;

{$APPTYPE CONSOLE}

uses
  System.SysUtils,
{$I ..\..\uses_include.inc}
  ;

const
  // declare video filename
  VIDEO_FILE_NAME = 'Resource\768x576.avi';
  // declare escape char
  ESCAPE_CHAR = 27;

var
  // declate an opencv video file capture object, users can use this object to
  // interact with the video file, get/set properties and also grab video frames
  capture: pCVCapture;
  // declare an opencv image pointer variable
  frame: pIplImage;
  // declate gray and threshold images
  gray, threshold: pIplImage;
  // declare a key variable to get user key pressed
  key: integer;
  // declate state variable
  need_creation: boolean;

  C: TCvSize;
  P: pCvArr;
  CC: pCvSize;

begin
  try
    // set state variable
    need_creation := true;
    // create capture object for specific video filename
    capture := cvCreateFileCapture(VIDEO_FILE_NAME);
    // check if capture assigned, if not then it means that opencv can not open
    // the requested file, opencv uses VFW to open the files so some file formats
    // are not fully supported (can be enhence with FFMPEG support but this is
    // beyond our scope right now
    if Assigned(capture) then
    begin
      // create display window
      cvNamedWindow('video');
      // create display window
      cvNamedWindow('threshold');
      // reset user key pressed
      key := 0;
      // loop while user didn't press ESCAPE
      while key <> ESCAPE_CHAR do
      begin
        // start grabbing frames, single frame at a time, this method is a
        // combination of two methods one grab frame and the other advances to the
        // next frame
        //
        // REMARK: do not (!!!) release "frame" object since it is used internally
        // by the capture object is its memory is release when the "capture" object
        // is being destroyed
        frame := cvQueryFrame(capture);
        // check if frame is valid, when you reach end-of-file "frame" object
        // starts to be NIL (since the method advances to the next frame each time
        // is is called...)
        if Assigned(frame) then
        begin
          // check if needs creation
          if need_creation then
          begin
            // create images at the same size as frame (using cvGetSize) but with
            // a different color depth, we want erode the image and that can be
            // done only in greyscale so we need to create a single 8bit channel
            // image but both the conversion and the threshold images
            // P:=pCvArr(@frame);
            C := cvGetSize(pCvArr(frame));
            gray := cvCreateImage(C, IPL_DEPTH_8U, 1);
            threshold := cvCreateImage(C, IPL_DEPTH_8U, 1);
            // reset state variable
            need_creation := false;
          end;
          // convert frame into greyscale, this function can convert to many
          // different color types, see third parameter consts for more details
          cvCvtColor(frame, gray, CV_RGB2GRAY);
          // threshold the image, there are many threshold methods and options
          // but here we use a simple one, binary fixed threshold, see third
          // parameter consts for more options
          cvThreshold(gray, threshold, 128, 255, CV_THRESH_BINARY);
          // for example: replace this line with the above line and see what it does
          // cvThreshold(gray,threshold,128,255,CV_THRESH_BINARY_INV);

          // show frame in window
          cvShowImage('video', frame);
          // show erode in second window
          cvShowImage('threshold', threshold);
        end; // if
        // wait for user key, delay is in msec so 1000msec = 1sec wait period
        key := cvWaitKey(50);
      end;
      // destroy display windows
      cvDestroyAllWindows;
      // release "capture" object and its related memory
      cvReleaseCapture(capture);
    end;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;

end.