When I trying to run the code below i am getting error

edit

i am using python 2.7 and opencv 2.4.13. The code is

# -*- coding: cp1254 -*-

import cv2

import numpy as np


def sift_detector(new_image, template):

    image1=cv2.cvtColor(new_image,cv2.COLOR_BGR2GRAY)
    image2=template
    sift=cv2.SIFT()
    keypoints1, descriptors1=sift.detectAndCompute(image1,None)
    keypoints2, descriptors2=sift.detectAndCompute(image2,None)
    FLANN_INDEX_KDTREE=0
    index_param=dict(algorithm=FLANN_INDEX_KDTREE,trees=3)
    search_params=dict(checks=100)

    flann=cv2.FlannBasedMatcher(index_params,search_params)
    matches=flann.knnMatch(descriptors1,descriptors2,k=2)

    good_matches=[]
    for m,n in matches:
        if m.distance < 0.7 * n.distance:
            good_matches.append(m)
        return len(good_matches)

cap =cv2.VideoCapture(0)

template=cv2.imread("ben.jpg",0)

while True:

    ret,frame=cap.read()
    height, width= frame.shape[:2]
    top_left_x=width/3
    top_left_y=(height/2) + (height/4)
    bottom_right_x= (width/3)*2
    bottom_right_y= (height/2) - (height/4)

    cv2.rectangle(frame, (top_left_x,top_left_y), (bottom_right_x,bottom_right_y),(255,0,0),3)
    cropped=frame[bottom_right_y:top_left_y,bottom_right_x: top_left_x]
    frame=cv2.flip(frame,1)
    matches=sift_detector(cropped,template)
    cv2.putText(frame,str(matches),(450,450),cv2.FONT_HERSHEY_COMPLEX,2,(0,255,0),3)
    threshold=15
    if matches > threshold:
        cv2.rectangle(frame, (top_left_x,top_left_y), (bottom_right_x,bottom_right_y),(255,125,0),3)
        cv2.putText(frame,"object found", (50,50), cv2.FONT_HERSHEY_COMPLEX,2,(255,255,0),2)


    cv2.imshow("after process",frame)
    if cv2.waitKey(1)==13:
        break

cap.release()

cv2.destroyAllWindows()

And the error is

Traceback (most recent call last):
  File "C:\Users\Ahmet\Desktop\artificial intelligence\opencv çalışmaları\mini project 5.py", line 41, in <module>

    matches=sift_detector(cropped,template)

  File "C:\Users\Ahmet\Desktop\artificial intelligence\opencv çalışmaları\mini project 5.py", line 10, in sift_detector

keypoints1, descriptors1=sift.detectAndCompute(image1,None)

error: C:\build\2_4_winpack-bindings-win64-vc14-static\opencv\modules\nonfree\src\sift.cpp:724: error: (-5) image is empty or has incorrect depth (!=CV_8U) in function cv::SIFT::operator ()