Added sepia tone

digital_image_processing/sepia.py

@@ -0,0 +1,54 @@
+"""
+    Implemented an algorithm using opencv to tone an image with sepia technique
+"""
+
+from cv2 import imread, imshow, waitKey, destroyAllWindows
+
+
+def make_sepia(img, factor: int):
+    """ Function create sepia tone. Source: https://en.wikipedia.org/wiki/Sepia_(color) """
+    pixel_h, pixel_v = img.shape[0], img.shape[1]
+
+    def to_grayscale(blue, green, red):
+        """
+        Helper function to create pixel's greyscale representation
+        Src: https://pl.wikipedia.org/wiki/YUV
+        """
+        return 0.2126 * red + 0.587 * green + 0.114 * blue
+
+    def normalize(value):
+        """ Helper function to normalize R/G/B value -> return 255 if value > 255"""
+        return value if value <= 255 else 255
+
+    for i in range(pixel_h):
+        for j in range(pixel_v):
+            greyscale = int(to_grayscale(*img[i][j]))
+            img[i][j] = [
+                normalize(greyscale),
+                normalize(greyscale + factor),
+                normalize(greyscale + 2 * factor),
+            ]
+
+    return img
+
+
+if __name__ == "__main__":
+    # read original image
+    img = imread("image_data/lena.jpg", 1)
+    img1 = imread("image_data/lena.jpg", 1)
+    img2 = imread("image_data/lena.jpg", 1)
+    img3 = imread("image_data/lena.jpg", 1)
+
+    # convert with sepia with different factor's value
+    sepia_10 = make_sepia(img, 10)
+    sepia_20 = make_sepia(img1, 20)
+    sepia_30 = make_sepia(img2, 30)
+    sepia_40 = make_sepia(img3, 40)
+
+    # show result images
+    imshow("Original image with sepia (factor: 10)", img)
+    imshow("Original image with sepia (factor: 20)", img1)
+    imshow("Original image with sepia (factor: 30)", img2)
+    imshow("Original image with sepia (factor: 40)", img3)
+    waitKey(0)
+    destroyAllWindows()

digital_image_processing/test_digital_image_processing.py

@@ -9,6 +9,7 @@
 import digital_image_processing.filters.convolve as conv
 import digital_image_processing.change_contrast as cc
 import digital_image_processing.convert_to_negative as cn
+import digital_image_processing.sepia as sp
 from cv2 import imread, cvtColor, COLOR_BGR2GRAY
 from numpy import array, uint8
 from PIL import Image
@@ -68,3 +69,8 @@ def test_median_filter():
 def test_sobel_filter():
     grad, theta = sob.sobel_filter(gray)
     assert grad.any() and theta.any()
+
+
+def test_sepia():
+    sepia = sp.make_sepia(img, 20)
+    assert sepia.all()