python 图像处理，,cv2.thresh

python 图像处理，,cv2.thresh

cv2.threshold介绍，如下图所示，每个数字代表起本身的灰度值大小

cv2.threshod接收５种类参数形式，分别是cv2.THRESH_BINARY，cv2.THRESH_BINARY_INV，cv2.THRESH_TRUNC ，cv2.THRESH_TOZERO,cv2.THRESH_TOZERO_INV

(1)THRESH_BINARY(Binary Thresholding)

# Binary Threshold,原图像素＞阈值，该像素点的值保持不变，否则为０．即大于阈值的部分变成像素最大值，小于阈值的部分变为０if src(x,y) > thresh  dst(x,y) = maxValueelse  dst(x,y) = 0

(2)THRESH_BINARY_INV(Inverse Binary Thresholding)

# Inverse Binary Threshold，原图像素＜阈值，该像素点的值为０，否则保持不变．与（１）相反，大于阈值的部分变为０，小于阈值的部分变成像素最大值if src(x,y) > thresh  dst(x,y) = 0else  dst(x,y) = maxValue

(3)THRESH_TRUNC(TruncateThresholding)

# Truncate Threshold，原图像素＞阈值，该像素点的值等于阈值，否则保持不变．即，将所有像素变成阈值以下水平if src(x,y) > thresh  dst(x,y) = threshelse  dst(x,y) = src(x,y)

(4)THRESH_TOZERO(Threshold to Zero)

# Threshold to Zeroif src(x,y) > thresh  dst(x,y) = src(x,y)else  dst(x,y) = 0

(5)THRESH_TOZERO_INV(Inverted Threshold to Zero)

# Inverted Threshold to Zeroif src(x,y) > thresh  dst(x,y) = 0else  dst(x,y) = src(x,y)

以上图为例，python代码为：

‘‘‘     OpenCV Threshold Example  Copyright 2015 by Satya Mallick <spmallick@gmail.com>‘‘‘# import opencv import cv2 # Read image src = cv2.imread("threshold.png", cv2.IMREAD_GRAYSCALE); # Basic threhold example th, dst = cv2.threshold(src, 0, 255, cv2.THRESH_BINARY); cv2.imwrite("opencv-threshold-example.jpg", dst); # Thresholding with maxValue set to 128th, dst = cv2.threshold(src, 0, 128, cv2.THRESH_BINARY); cv2.imwrite("opencv-thresh-binary-maxval.jpg", dst); # Thresholding with threshold value set 127 th, dst = cv2.threshold(src,127,255, cv2.THRESH_BINARY); cv2.imwrite("opencv-thresh-binary.jpg", dst); # Thresholding using THRESH_BINARY_INV th, dst = cv2.threshold(src,127,255, cv2.THRESH_BINARY_INV); cv2.imwrite("opencv-thresh-binary-inv.jpg", dst); # Thresholding using THRESH_TRUNC th, dst = cv2.threshold(src,127,255, cv2.THRESH_TRUNC); cv2.imwrite("opencv-thresh-trunc.jpg", dst); # Thresholding using THRESH_TOZERO th, dst = cv2.threshold(src,127,255, cv2.THRESH_TOZERO); cv2.imwrite("opencv-thresh-tozero.jpg", dst); # Thresholding using THRESH_TOZERO_INV th, dst = cv2.threshold(src,127,255, cv2.THRESH_TOZERO_INV); cv2.imwrite("opencv-thresh-to-zero-inv.jpg", dst); 

结果图：

(1) (2) (3)

(4) (5)
参考连接：

http://www.learnopencv.com/opencv-threshold-python-cpp/

http://docs.opencv.org/trunk/d7/d4d/tutorial_py_thresholding.html

python 图像处理