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Examples/opencv2-python/simple/Example2/example2.py

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+# This script shows how to do simple processing on frames comming from a camera in OpenCV.
+# Kim S. Pedersen, 2015
+
+import cv2 # Import the OpenCV library
+import numpy as np # We also need numpy
+
+
+from pkg_resources import parse_version
+OPCV3 = parse_version(cv2.__version__) >= parse_version('3')
+
+def capPropId(prop):
+    """returns OpenCV VideoCapture property id given, e.g., "FPS
+       This is needed because of differences in the Python interface in OpenCV 2.4 and 3.0
+    """
+    return getattr(cv2 if OPCV3 else cv2.cv, ("" if OPCV3 else "CV_") + "CAP_PROP_" + prop)
+    
+
+print("OpenCV version = " + cv2.__version__)
+    
+
+# Define some constants
+lowThreshold = 35
+ratio = 3
+kernel_size = 3
+
+
+# Open a camera device for capturing
+cam = cv2.VideoCapture(0)
+
+
+if not cam.isOpened(): # Error
+    print("Could not open camera")
+    exit(-1)
+    
+# Get camera properties
+width = int(cam.get(capPropId("FRAME_WIDTH"))) 
+height = int(cam.get(capPropId("FRAME_HEIGHT")))
+print("width = " + str(width) + ", Height = " + str(height))
+
+    
+# Open a window
+WIN_RF = "Example 2"
+cv2.namedWindow(WIN_RF)
+cv2.moveWindow(WIN_RF, 100, 100)
+
+
+# Preallocate memory
+#gray_frame = np.zeros((height, width), dtype=np.uint8)
+
+while cv2.waitKey(4) == -1: # Wait for a key pressed event
+    retval, frameReference = cam.read() # Read frame
+    
+    if not retval: # Error
+        print(" < < <  Game over!  > > > ")
+        exit(-1)
+    
+    # Convert the image to grayscale
+    gray_frame = cv2.cvtColor( frameReference, cv2.COLOR_BGR2GRAY )
+    
+    # Reduce noise with a kernel 3x3
+    edge_frame = cv2.blur( gray_frame, (3,3) )
+
+    # Canny detector
+    cv2.Canny( edge_frame, lowThreshold, lowThreshold*ratio, edge_frame, kernel_size )
+    
+    # Show frames
+    cv2.imshow(WIN_RF, edge_frame)
+    
+# Close all windows
+cv2.destroyAllWindows()
+
+# Finished successfully