i have written code for marking an object in two frames,but the object is not getting marked...can anyone help me with a correct code?

Question

import opencv.cv as cv
import opencv.highgui as hg
import sys
roi_x0 = 0
roi_y0 = 0
roi_x1 = 0
roi_y1 = 0
startDraw = 0
image = cv.IplImage
window_name = "Press c to capture"
draw = "Mark"
crop = "ROI"
result = "Result"
def on_mouse(event,x,y,flag,param):
    global startDraw,im,roi_x0,roi_x1,roi_y0,roi_y1
    if(event == hg.CV_EVENT_LBUTTONDOWN):
        if(startDraw == 0):
            roi_x0 = x
            roi_y0 = y
            startDraw = 1
        else:
            roi_x1 = x
            roi_y1 = y
            startDraw = 0
    if(event==hg.CV_EVENT_MOUSEMOVE and startDraw == 1):
        image2 = cv.cvCloneImage(image)
        cv.cvRectangle(image2,cv.cvPoint(roi_x0,roi_y0),cv.cvPoint(x,y),cv.CV_RGB(255,0,255),1)
        hg.cvShowImage(draw,image2)
def main():
    global image
    capture = hg.cvCreateCameraCapture(0)

    hg.cvNamedWindow(window_name,1)
    hg.cvSetMouseCallback(window_name,on_mouse,None)
    flag = 1
    while flag == 1:
 image = hg.cvQueryFrame(capture)
     key = hg.cvWaitKey(2)
 im = image
 if key == 'e':
     sys.exit()
 if key == 'a':
     if roi_x0<roi_x1 and roi_y0<roi_y1:
                r = cv.cvRect(roi_x0,roi_y0,roi_x1-roi_x0,roi_y1-roi_y0)
                cropped = cv.cvCreateImage( cv.cvSize(roi_x1-roi_x0, roi_y1-roi_y0), 8, 3)
                src_region = cv.cvGetSubRect(image,r)
                cv.cvCopy(src_region, cropped)  
  #cv.cvReleaseImage(image)                                      
            if roi_x1<roi_x0 and roi_y1<roi_y0:
                r = cv.cvRect(roi_x0,roi_y0,roi_x0-roi_x1,roi_y0-roi_y1)
                cropped = cv.cvCreateImage( cv.cvSize(roi_x0-roi_x1, roi_y0-roi_y1), 8, 3)      
                src_region = cv.cvGetSubRect(image, r)
                cv.cvCopy(src_region, cropped)
  #cv.cvReleaseImage(image)
     hg.cvSaveImage("1.jpg",src_region)
     res_width = 640 - src_region.width + 1
     res_height = 480 - src_region.height + 1
     res = cv.cvCreateImage(cv.cvSize(res_width,res_height),cv.IPL_DEPTH_32F,1)
     hg.cvDestroyAllWindows()
     flag = 0 
 else:
     hg.cvShowImage(window_name, image)
    while True:

 image = hg.cvQueryFrame(capture)
 hg.cvShowImage(result,image)
 key = hg.cvWaitKey(2)
 if key == 'e':
      sys.exit()
 elif key == 'c':
  hg.cvSaveImage("Image1.jpg",image)
  im = hg.cvLoadImage("Image1.jpg")
         cv.cvMatchTemplate(image,src_region,res, cv.CV_TM_SQDIFF )
  minval, maxval, minloc, maxloc = cv.cvMinMaxLoc( res, 0 );
  cv.cvRectangle( im, cv.cvPoint(minloc.x, minloc.y),cv.cvPoint( minloc.x + src_region.width, minloc.y + src_region.height ),cv.cvScalar( 0, 0, 255, 0 ), 1, 0, 0 );
  hg.cvSaveImage("ggg.jpg",im)
  hg.cvWaitKey(2)
  hg.cvDestroyWindow(result) 
                cv.cvReleaseImage(image)
if __name__ == "__main__":
    main()