数字图像处理100问—16 Prewitt 滤波器

提示：内容整理自：https://github.com/gzr2017/ImageProcessing100Wen
CV小白从0开始学数字图像处理

Prewitt 滤波器是用于边缘检测的一种滤波器，使用下式定义：

      (a)纵向            (b)横向
      -1 -1 -1          -1 0 1
K = [  0  0  0 ]  K = [ -1 0 1 ]
       1  1  1          -1 0 1

代码如下：

CV2计算机视觉库

import cv2
import numpy as np

img = cv2.imread("imori.jpg").astype(np.float)
H, W, C = img.shape

b = img[:, :, 0].copy()
g = img[:, :, 1].copy()
r = img[:, :, 2].copy()

gray = 0.2126 * r + 0.7152 * g + 0.0722 * b
gray = gray.astype(np.uint8)

K_size = 3

pad = K_size // 2
out = np.zeros((H + pad*2, W + pad*2), dtype=np.float)
out[pad:pad+H, pad:pad+W] = gray.copy().astype(np.float)
tmp = out.copy()

## Sobel vertical
K = [[-1., -1., -1.],[0., 0., 0.], [1., 1., 1.]]
## Sobel horizontal
#K = [[-1., 0., 1.],[-1., 0., 1.],[-1., 0., 1.]]

for y in range(H):
    for x in range(W):
        out[pad+y, pad+x] = np.sum(K * (tmp[y:y+K_size, x:x+K_size]))

out[out < 0] = 0
out[out > 255] = 255

out = out[pad:pad+H, pad:pad+W].astype(np.uint8)

cv2.imwrite("out.jpg", out)
cv2.imshow("result", out)
cv2.waitKey(0)
cv2.destroyAllWindows()

左：垂直
右：水平