Basic geometric transformations – OpenCV 3.4 with python 3 Tutorial 12

2 Comments

1. 

   Mustafa July 11, 2018 at 3:41 pm

   hi sergio
   my name ist mustafa im a student in germany and i have projekt with opencv. I saw your Tutorial 12 and would like to ask you how i can do the same with cv2.videocapture(0) .
   i would appreciate it if you could help me with this.

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   1. 

      Sergio Canu July 11, 2018 at 3:43 pm

      Hi Mustafa,
      it’s easy. It works in the same way but inside a loop, as for a video you need to process frame by frame.

      Here is the code for a video:

      import cv2
      import numpy as np
      
      cap = cv2.VideoCapture(0)
      
      # Git first frame to take the size of frame
      _, frame = cap.read()
      rows, cols, ch = frame.shape
      
      print("Height: ", rows)
      print("Width: ", cols)
      
      while True:
          _, frame = cap.read()
          scaled_img = cv2.resize(frame, None, fx=1 / 2, fy=1 / 2)
      
          matrix_t = np.float32([[1, 0, -100], [0, 1, -30]])
          translated_img = cv2.warpAffine(frame, matrix_t, (cols, rows))
      
          matrix_r = cv2.getRotationMatrix2D((cols / 2, rows / 2), 90, 0.5)
          rotated_img = cv2.warpAffine(frame, matrix_r, (cols, rows))
      
          cv2.imshow("Original image", frame)
          cv2.imshow("Scaled image", scaled_img)
          cv2.imshow("Translated image", translated_img)
          cv2.imshow("Rotated image", rotated_img)
      
          key = cv2.waitKey(1)
          if key == 27:
              break
              
      cap.release()
      cv2.destroyAllWindows()
      

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