Read and save images

Read image from disk

img = cv2.imread('path', flag)

Reads the image from the path provided. Here, flag = cv2.IMREAD_COLOR, cv2.IMREAD_GRAYSCALE, cv2.IMREAD_UNCHANGED determines whether the image is read as color, grayscale or as such, i.e. including the alpha channel. Alternatively, the flag can be specified as an integer, i.e. flag = 1,0,-1.

An image can be displayed in a named window:

cv2.imshow('name of window', img)

Not suprisingly, the first argument is the name of the window and the second one the image to be displayed. In order to admire the image on screen you need to tell OpenCV to wait for a key to be pressed:

k = cv2.waitKey(delay=0) & 0xff
if k == 27:
    cv2.destroyAllWindows()

delay is the lag in milliseconds, 0 means wait forever, & 0xff is needed on 64-Bit machines. if the esc-key is pressed (k==27) the opened window is destroyed. To be precise, cv2.destroyAllWindows() closes all open windows. A single named window can be closed with cv2.destroyWindow('name of window').

Save image to disk

cv2.imwrite('path',img)