From 9316618611967c26b98ce275fab238f735f2864e Mon Sep 17 00:00:00 2001
From: Shoaib Asgar <shoaib.mca19.du@gmail.com>
Date: Mon, 9 Dec 2019 07:59:01 +0530
Subject: [PATCH] digital_image_processing/convert_to_negative (#1216)

* digital_image_processing/convert_to_negative

* added doc

* added test code

* Update convert_to_negative.py
---
 .../convert_to_negative.py                    | 30 +++++++++++++++++++
 .../test_digital_image_processing.py          |  8 +++++
 2 files changed, 38 insertions(+)
 create mode 100644 digital_image_processing/convert_to_negative.py

diff --git a/digital_image_processing/convert_to_negative.py b/digital_image_processing/convert_to_negative.py
new file mode 100644
index 000000000..cba503938
--- /dev/null
+++ b/digital_image_processing/convert_to_negative.py
@@ -0,0 +1,30 @@
+"""
+    Implemented an algorithm using opencv to convert a colored image into its negative
+"""
+
+from cv2 import imread, imshow, waitKey, destroyAllWindows
+
+
+def convert_to_negative(img):
+    # getting number of pixels in the image
+    pixel_h, pixel_v = img.shape[0], img.shape[1]
+
+    # converting each pixel's color to its negative
+    for i in range(pixel_h):
+        for j in range(pixel_v):
+            img[i][j] = [255, 255, 255] - img[i][j]
+
+    return img
+
+
+if __name__ == "__main__":
+    # read original image
+    img = imread("image_data/lena.jpg", 1)
+
+    # convert to its negative
+    neg = convert_to_negative(img)
+
+    # show result image
+    imshow("negative of original image", img)
+    waitKey(0)
+    destroyAllWindows()
diff --git a/digital_image_processing/test_digital_image_processing.py b/digital_image_processing/test_digital_image_processing.py
index 02c1a2d3a..1a730b391 100644
--- a/digital_image_processing/test_digital_image_processing.py
+++ b/digital_image_processing/test_digital_image_processing.py
@@ -8,6 +8,7 @@ import digital_image_processing.filters.median_filter as med
 import digital_image_processing.filters.sobel_filter as sob
 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
 from cv2 import imread, cvtColor, COLOR_BGR2GRAY
 from numpy import array, uint8
 from PIL import Image
@@ -15,6 +16,13 @@ from PIL import Image
 img = imread(r"digital_image_processing/image_data/lena_small.jpg")
 gray = cvtColor(img, COLOR_BGR2GRAY)
 
+# Test: convert_to_negative()
+def test_convert_to_negative():
+    negative_img = cn.convert_to_negative(img)
+    # assert negative_img array for at least one True
+    assert negative_img.any()
+
+
 # Test: change_contrast()
 def test_change_contrast():
     with Image.open("digital_image_processing/image_data/lena_small.jpg") as img: