added contour detection tutorial

Author: x4nth055

README.md

@@ -29,6 +29,7 @@ This is a repository of all the tutorials of [The Python Code](https://www.thepy
         - [How to Use Transfer Learning for Image Classification using Keras in Python](https://www.thepythoncode.com/article/use-transfer-learning-for-image-flower-classification-keras-python). ([code](machine-learning/image-classifier-using-transfer-learning))
         - [How to Perform Edge Detection in Python using OpenCV](https://www.thepythoncode.com/article/canny-edge-detection-opencv-python). ([code](machine-learning/edge-detection))
         - [How to Detect Shapes in Images in Python](https://www.thepythoncode.com/article/detect-shapes-hough-transform-opencv-python). ([code](machine-learning/shape-detection))
+        - [How to Detect Contours in Images using OpenCV in Python](https://www.thepythoncode.com/article/contour-detection-opencv-python). ([code](machine-learning/contour-detection))
         - [How to Recognize Optical Characters in Images in Python](https://www.thepythoncode.com/article/optical-character-recognition-pytesseract-python). ([code](machine-learning/optical-character-recognition))
     - [Building a Speech Emotion Recognizer using Scikit-learn](https://www.thepythoncode.com/article/building-a-speech-emotion-recognizer-using-sklearn). ([code](machine-learning/speech-emotion-recognition))
     - [How to Convert Speech to Text in Python](https://www.thepythoncode.com/article/using-speech-recognition-to-convert-speech-to-text-python). ([code](machine-learning/speech-recognition))

machine-learning/contour-detection/README.md

@@ -0,0 +1,8 @@
+# [How to Detect Contours in Images using OpenCV in Python](https://www.thepythoncode.com/article/contour-detection-opencv-python)
+To run this:
+- `pip3 install -r requirements.txt`
+- To detect contour of the the image `thumbs_up_down.jpg` using 225 value of binary threshold conversion:
+    ```
+    python contour-detector.py thumbs_up_down.jpg 225
+    ```
+- For live detection, consider using `live-contour-detector.py` script.

machine-learning/contour-detection/contour-detector.py

@@ -0,0 +1,28 @@
+import cv2
+import matplotlib.pyplot as plt
+import sys
+
+# read the image
+image = cv2.imread(sys.argv[1])
+
+# convert to RGB
+image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
+
+# convert to grayscale
+gray = cv2.cvtColor(image, cv2.COLOR_RGB2GRAY)
+
+# create a binary thresholded image
+_, binary = cv2.threshold(gray, sys.argv[2], 255, cv2.THRESH_BINARY_INV)
+# show it
+plt.imshow(binary, cmap="gray")
+plt.show()
+
+# find the contours from the thresholded image
+contours, hierarchy = cv2.findContours(binary, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
+
+# draw all contours
+image = cv2.drawContours(image, contours, -1, (0, 255, 0), 2)
+
+# show the image with the drawn contours
+plt.imshow(image)
+plt.show()

machine-learning/contour-detection/live-contour-detector.py

@@ -0,0 +1,29 @@
+import cv2
+
+cap = cv2.VideoCapture(0)
+
+while True:
+    _, frame = cap.read()
+
+    # convert to grayscale
+    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
+
+    # create a binary thresholded image
+    _, binary = cv2.threshold(gray, 255 // 2, 255, cv2.THRESH_BINARY_INV)
+
+    # find the contours from the thresholded image
+    contours, hierarchy = cv2.findContours(binary, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
+
+    # draw all contours
+    image = cv2.drawContours(frame, contours, -1, (0, 255, 0), 2)
+
+    # show the images
+    cv2.imshow("gray", gray)
+    cv2.imshow("image", image)
+    cv2.imshow("binary", binary)
+
+    if cv2.waitKey(1) == ord("q"):
+        break
+
+cap.release()
+cv2.destroyAllWindows()

machine-learning/contour-detection/pancakes.jpg

@@ -0,0 +1,2 @@
+opencv-python
+matplotlib