手动实现cv2.inRange函数
时间: 2023-06-18 08:03:23 浏览: 65
下面是手动实现cv2.inRange函数的代码示例:
```python
import numpy as np
def inRange(img, lower, upper):
lower = np.array(lower)
upper = np.array(upper)
mask = np.zeros_like(img)
for c in range(img.shape[2]):
mask[:,:,c] = np.logical_and(img[:,:,c] >= lower[c], img[:,:,c] <= upper[c])
return np.all(mask, axis=2).astype(np.uint8) * 255
```
该函数接受三个参数:图像img,颜色范围的下限lower,颜色范围的上限upper。它会返回一个掩膜图像,其中在颜色范围内的像素值为255,否则为0。
该函数的实现方式是首先将颜色范围下限和上限转换为numpy数组,然后创建一个与输入图像相同大小的掩膜图像。接下来,对于每个通道,我们使用numpy.logical_and函数计算该通道中在颜色范围内的像素,并将结果存储在掩膜图像上。最后,我们使用numpy.all函数将所有通道的掩膜图像合并,并将结果转换为灰度图像。
相关问题
cv2.GaussianBlur函数的实现
cv2.GaussianBlur函数的实现基于高斯卷积的原理,其具体实现步骤如下:
1.根据高斯核的大小和标准差生成高斯核:
```python
sigma = 1
ksize = (5, 5)
kernel = cv2.getGaussianKernel(ksize[0], sigma)
kernel = np.dot(kernel, kernel.T)
```
其中,sigma表示高斯核的标准差,ksize表示高斯核的大小,kernel表示生成的高斯核。
2.对输入图像进行边界扩充:
```python
border = ksize[0] // 2
img = cv2.copyMakeBorder(src, border, border, border, border, cv2.BORDER_DEFAULT)
```
其中,border表示边界宽度,cv2.copyMakeBorder函数可以对图像进行边界扩充。
3.对图像进行卷积操作:
```python
dst = np.zeros_like(img)
for i in range(border, img.shape[0] - border):
for j in range(border, img.shape[1] - border):
dst[i, j] = np.sum(kernel * img[i - border:i + border + 1, j - border:j + border + 1])
dst = dst[border:dst.shape[0] - border, border:dst.shape[1] - border]
```
其中,dst表示输出图像,np.zeros_like函数创建一个与输入图像大小相同的全黑图像,然后对图像进行卷积操作,最后截取中间部分得到输出图像。
完整代码如下:
```python
import cv2
import numpy as np
img = cv2.imread('image.jpg')
sigma = 1
ksize = (5, 5)
kernel = cv2.getGaussianKernel(ksize[0], sigma)
kernel = np.dot(kernel, kernel.T)
border = ksize[0] // 2
img = cv2.copyMakeBorder(img, border, border, border, border, cv2.BORDER_DEFAULT)
dst = np.zeros_like(img)
for i in range(border, img.shape[0] - border):
for j in range(border, img.shape[1] - border):
dst[i, j] = np.sum(kernel * img[i - border:i + border + 1, j - border:j + border + 1])
dst = dst[border:dst.shape[0] - border, border:dst.shape[1] - border]
cv2.imshow('Original', img)
cv2.imshow('Gaussian Filter', dst)
cv2.waitKey(0)
cv2.destroyAllWindows()
```
该代码与使用cv2.GaussianBlur函数的效果相同,但是是手动实现高斯滤波的过程,可以更好地理解高斯滤波的原理和实现过程。
python手动实现cv2.canny算子
好的,下面是Python手动实现cv2.canny算子的代码:
```python
import cv2
import numpy as np
def canny(image, low_threshold, high_threshold):
# Convert the image to grayscale
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
# Apply Gaussian blur to the grayscale image
blur = cv2.GaussianBlur(gray, (5, 5), 0)
# Apply the Sobel operator to the blurred image
sobelx = cv2.Sobel(blur, cv2.CV_64F, 1, 0, ksize=3)
sobely = cv2.Sobel(blur, cv2.CV_64F, 0, 1, ksize=3)
# Compute the gradient magnitude and direction
mag = np.sqrt(sobelx**2 + sobely**2)
theta = np.arctan2(sobely, sobelx)
# Convert the gradient direction to degrees
angle = np.rad2deg(theta)
# Apply non-maximum suppression
nms = np.zeros_like(mag)
for i in range(1, nms.shape[0]-1):
for j in range(1, nms.shape[1]-1):
if (angle[i,j] <= 22.5 and angle[i,j] > -22.5) or (angle[i,j] <= -157.5 and angle[i,j] > 157.5):
if mag[i,j] > mag[i,j-1] and mag[i,j] > mag[i,j+1]:
nms[i,j] = mag[i,j]
elif (angle[i,j] <= 67.5 and angle[i,j] > 22.5) or (angle[i,j] <= -112.5 and angle[i,j] > -157.5):
if mag[i,j] > mag[i-1,j-1] and mag[i,j] > mag[i+1,j+1]:
nms[i,j] = mag[i,j]
elif (angle[i,j] <= 112.5 and angle[i,j] > 67.5) or (angle[i,j] <= -67.5 and angle[i,j] > -112.5):
if mag[i,j] > mag[i-1,j] and mag[i,j] > mag[i+1,j]:
nms[i,j] = mag[i,j]
elif (angle[i,j] <= 157.5 and angle[i,j] > 112.5) or (angle[i,j] <= -22.5 and angle[i,j] > -67.5):
if mag[i,j] > mag[i-1,j+1] and mag[i,j] > mag[i+1,j-1]:
nms[i,j] = mag[i,j]
# Apply hysteresis thresholding
edges = np.zeros_like(nms)
edges[nms > high_threshold] = 255
edges[nms < low_threshold] = 0
for i in range(1, edges.shape[0]-1):
for j in range(1, edges.shape[1]-1):
if edges[i,j] == 255:
if edges[i-1,j-1] == 0:
edges[i-1,j-1] = 128
if edges[i-1,j] == 0:
edges[i-1,j] = 128
if edges[i-1,j+1] == 0:
edges[i-1,j+1] = 128
if edges[i,j-1] == 0:
edges[i,j-1] = 128
if edges[i,j+1] == 0:
edges[i,j+1] = 128
if edges[i+1,j-1] == 0:
edges[i+1,j-1] = 128
if edges[i+1,j] == 0:
edges[i+1,j] = 128
if edges[i+1,j+1] == 0:
edges[i+1,j+1] = 128
edges[edges == 128] = 255
edges[edges != 255] = 0
return edges.astype(np.uint8)
```
其中,参数`image`为待处理的图像,`low_threshold`和`high_threshold`分别为低阈值和高阈值。返回值为处理后的二值图像。
该函数的实现过程如下:
1. 将图像转换为灰度图像;
2. 对灰度图像进行高斯模糊;
3. 对模糊后的图像进行Sobel算子计算,得到水平方向和垂直方向的梯度;
4. 计算每个像素点的梯度幅值和梯度方向;
5. 对梯度方向进行非极大值抑制,保留每个方向上梯度幅值最大的像素点;
6. 对抑制后的图像进行双阈值边缘连接,将高于高阈值的像素点视为强边缘,低于低阈值的像素点视为背景,介于两者之间的像素点视为弱边缘;
7. 对弱边缘像素点进行连接,将其与其相邻的强边缘像素点连接起来,最终得到二值图像。
需要注意的是,该函数的实现并不能完全等同于cv2.canny函数的实现,因为在非极大值抑制和边缘连接的过程中可能存在一些差异。