亚像素边缘检测python

亚像素边缘检测是一种边缘检测算法，它可以在像素级别上检测图像中的边缘。Python中有许多库和工具可用于实现亚像素边缘检测，下面是一个使用OpenCV库实现亚像素边缘检测的示例代码：

import cv2

# 读取图像
img = cv2.imread('image.jpg')

# 转换为灰度图像
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# 计算梯度
sobelx = cv2.Sobel(gray, cv2.CV_64F, 1, 0, ksize=3)
sobely = cv2.Sobel(gray, cv2.CV_64F, 0, 1, ksize=3)

# 计算梯度的大小和方向
mag, angle = cv2.cartToPolar(sobelx, sobely, angleInDegrees=True)

# 应用非极大值抑制
kernel_size = 3
m, n = mag.shape
for i in range(1, m - 1):
    for j in range(1, n - 1):
        if (angle[i, j] >= 0 and angle[i, j] < 22.5) or (angle[i, j] >= 157.5 and angle[i, j] <= 180):
            a = mag[i, j - 1]
            b = mag[i, j]
            c = mag[i, j + 1]
        elif (angle[i, j] >= 22.5 and angle[i, j] < 67.5):
            a = mag[i - 1, j - 1]
            b = mag[i, j]
            c = mag[i + 1, j + 1]
        elif (angle[i, j] >= 67.5 and angle[i, j] < 112.5):
            a = mag[i - 1, j]
            b = mag[i, j]
            c = mag[i + 1, j]
        elif (angle[i, j] >= 112.5 and angle[i, j] < 157.5):
            a = mag[i - 1, j + 1]
            b = mag[i, j]
            c = mag[i + 1, j - 1]
        if (b > a and b > c):
            mag[i, j] = b
        else:
            mag[i, j] = 0

# 应用双阈值算法
low_threshold = 0.05 * mag.max()
high_threshold = 0.15 * mag.max()
threshold = cv2.Canny(img, low_threshold, high_threshold)

# 应用亚像素边缘检测
subpixel_threshold = 0.5
lines = cv2.HoughLinesP(threshold, 1, cv2.PI / 180, 50, minLineLength=50, maxLineGap=5)
for line in lines:
    x1, y1, x2, y2 = line[0]
    dx = x2 - x1
    dy = y2 - y1
    length = cv2.sqrt(dx * dx + dy * dy)[0]
    if length > 0:
        vx = dx / length
        vy = dy / length
        x = x1
        y = y1
        while length > 0:
            length -= subpixel_threshold
            x += subpixel_threshold * vx
            y += subpixel_threshold * vy
            cv2.circle(img, (int(x), int(y)), 1, (0, 255, 0), -1)

# 显示结果
cv2.imshow('result', img)
cv2.waitKey(0)

这段代码首先读取图像并将其转换为灰度图像，然后计算图像的梯度，应用非极大值抑制和双阈值算法来检测边缘，最后使用Hough变换和亚像素边缘检测来检测和绘制边缘。