display cv2 image in jupyter notebook
# matplotlib interprets images in RGB format, but OpenCV uses BGR format
# so to convert the image so that it's properly loaded, convert it before loading
img = cv2.imread('filename.ext') # this is read in BGR format
rgb_img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB) # this converts it into RGB
plt.imshow(rgb_img)
plt.show()