如何使 `cv2.imshow` 输出与 `plt.imshow` 输出相同？

Question

How can I make the cv2.imshow output the same as the plt.imshow output?

# loading image
img0 = cv2.imread("image.png")
# converting to gray scale
gray = cv2.cvtColor(img0, cv2.COLOR_BGR2GRAY)

# remove noise
img = cv2.GaussianBlur(gray, (3, 3), 0)

# convolute with proper kernels
laplacian = cv2.Laplacian(img, cv2.CV_64F)
sobelx = cv2.Sobel(img, cv2.CV_64F, 1, 0, ksize=5)  # x
sobely = cv2.Sobel(img, cv2.CV_64F, 0, 1, ksize=5)  # y
imgboth = cv2.addWeighted(sobelx, 0.5, sobely, 0.5, 0)

plt.imshow(imgboth, cmap='gray')
plt.show()

cv2.imshow("img", cv2.resize(imgboth, (960, 540)))
cv2.waitKey(0)
cv2.destroyAllWindows()
       

original image

plt.output

cv2.imshow

Answer 1

# ...
canvas = imgboth.astype(np.float32)
canvas /= np.abs(imgboth).max()
canvas += 0.5
cv.namedWindow("canvas", cv.WINDOW_NORMAL)
cv.imshow("canvas", canvas)
cv.waitKey()
cv.destroyWindow("canvas")

only looks different because you posted thumbnails, not the original size image.

when you give imshow floating point values, which you do because laplacian and sobelx are floating point, then it assumes a range of 0.0 .. 1.0 as black .. white.

matplotlib automatically scales data. OpenCV's imshow doesn't. both behaviors have pros and cons.