How to resize an image but keep pixel's value with python

Question

I'm dealing with some images, and I'd like to resize them from 1080 * 1920 to 480 * 640. I have classified every single pixel into a specific class so each of them has a unique value. However, those value of pixel would changed if I resized image.

python
resized = cv2.resize(image, (640, 480), interpolation = cv2.INTER_AREA)
print(set(resized.flat)) --> a dict {0,1,2,3,4……,38,39,40}
print(set(image.flat)) --> a dict {0,10,40}

# image size is 1080 * 1920
# resized size is 480 * 640

desired_image = cv2.imread(desired_image_path,cv2.IMREAD_GRAYSCALE).astype(np.uint8)
print(set(desired_image.flat)) --> a dict {0,10,40}

# desired_image size is 480 * 640

I expect to have the desired image which have the size of 480 * 640 without any crop and keep the pixel's value same. Now I have the correct size but value of pixels change a lot.

Answer 1

If i understand you correctly, you want to resize the image without creating new pixel values. This can be done by setting the interpolation parameter of cv2.resize to INTER_NEAREST

resized = cv2.resize(image, (640, 480), interpolation = cv2.INTER_NEAREST)

Source: https://docs.opencv.org/2.4/modules/imgproc/doc/geometric_transformations.html#resize