python - OpenCV error: Assertion failed (mask.size == src1.size) in binary_op -

i trying place png image image of hat on head of webcam feed.

import cv2 import numpy np  face_cascade = cv2.cascadeclassifier('haarcascades/haarcascade_frontalface_default.xml')  # load overlay image: hat.png imghat = cv2.imread('hat2.png', -1)  print imghat none  # create mask hat imghatgray = cv2.cvtcolor(imghat, cv2.color_bgr2gray) #cv2.imwrite("imghatgray.png", imghatgray)  ret, orig_mask = cv2.threshold(imghatgray, 0, 255, cv2.thresh_binary) #cv2.imwrite("orig_mask.png", orig_mask)  # create inverted mask hat orig_mask_inv = cv2.bitwise_not(orig_mask) #cv2.imwrite("orig_mask_inv.png", orig_mask_inv)  # convert hat image bgr # , save original image size (used later when re-sizing image) imghat = imghat[:,:,0:3] orighatheight, orighatwidth = imghat.shape[:2]  video_capture = cv2.videocapture(0)  while true:      ret, frame = video_capture.read()      gray = cv2.cvtcolor(frame, cv2.color_bgr2gray)      faces = face_cascade.detectmultiscale(gray, 1.3, 5, flags=cv2.cv.cv_haar_scale_image)      (x, y, w, h) in faces:         print "x : %d , y : %d, w: %d, h: %d " %(x,y,w,h)         cv2.rectangle(frame, (x,y), (x+w, y+h), (255,0,0), 2)         #cv2.rectangle(frame, (x-15,y-h), (x+w+15, y), (255,255,0), 2)          hatwidth = w         hatheight = hatwidth * orighatheight / orighatwidth              roi_gray = gray[y:y+h, x:x+w]             roi_color = frame[y:y+h, x:x+w]          # center hat         x1 = x - 15         y1 = y - h         x2 = x1 + w + 30         y2 = y1 + h          #cv2.rectangle(frame, (x1,y1), (x2, y2), (0,255,0), 2)          # check clipping         if x1 < 0:             x1 = 0         if y1 < 0:             y1 = 0         if x2 > 640:             x2 = w         if y2 > 360:             y2 = h           print "x1: %d , y1 : %d, x2: %d, y2: %d " %(x1,y1,x2,y2)         # re-calculate width , height of hat image         hatwidth = x2 - x1         hatheight = y2 - y1          cv2.rectangle(frame, (x1,y1), (x2, y2), (255,255,0), 2)         print "hatwidth: %d, hatheight: %d" %(hatwidth, hatheight)               # re-size original image , masks hat sizes         # calcualted above         hat = cv2.resize(imghat, (hatwidth,hatheight), interpolation = cv2.inter_area)         mask = cv2.resize(orig_mask, (hatwidth,hatheight), interpolation = cv2.inter_area)         mask_inv = cv2.resize(orig_mask_inv, (hatwidth,hatheight), interpolation = cv2.inter_area)          # take roi hat background equal size of hat image         roi = roi_color[y1:y2, x1:x2]          # roi_bg contains original image hat not         # in region size of hat.         roi_bg = cv2.bitwise_and(roi,roi,mask = mask_inv)          # roi_fg contains image of hat hat         roi_fg = cv2.bitwise_and(hat,hat,mask = mask)          # join roi_bg , roi_fg         dst = cv2.add(roi_bg,roi_fg)          # place joined image, saved dst on original image         roi_color[y1:y2, x1:x2] = dst          break        # display resulting frame         cv2.imshow('video', frame)           if cv2.waitkey(1) & 0xff == ord('q'):             break  # when done, release capture video_capture.release() cv2.destroyallwindows() 

when execute program, camera opens , closes abruptly. error shown in below line -

roi_bg = cv2.bitwise_and(roi, roi, mask = mask_inv)

the error

assertion failed (mask.size == src1.size) 

i.e. size of mask image does't match size of source image you're doing bitwise_and on

the source image roi

roi = roi_color[ y1:y2, x1:x2 ] 

which looks y2-y1 x x2-x1

the mask size

mask = cv2.resize(orig_mask, (hatwidth,hatheight), interpolation = cv2.inter_area) 

which looks hatwidth x hatheight i.e. (x2-x1) x (y2-y1) unless parentheses invert order of width , height - i'm not python guru seems unlikely.