Image binarization processing of opencv

opencvBinarization operation is divided into：There are two types of global threshold and local threshold.The image needs to be grayscaled before image binarization.

全局阈值

The global threshold is divided into：There are two types of manual threshold and automatic threshold.

手动阈值
opencv函数：

threshold(gray_src, dst, threshold_value, threshold_max,THRESH_BINARY);
//原图,目标图,known threshold（Threshold for comparison）,阈值最大值,阈值类型（threshold()函数支持的对图像取阈值的方法由其确定）

There are methods for this function to threshold the image5种：

• THRESH_BINARY:过门限的值为最大值,其他值为0
  

• THRESH_BINARY_INV:过门限的值为0,其他值为最大值
  

• THRESH_TRUNC:过门限的值为门限值,其他值不变
  

• THRESH_TOZERO:过门限的值不变,其他设置为0
  

• THRESH_TOZERO_INV:过门限的值为0,其他不变
  
  自动阈值
  Automatic thresholds are divided into大津法和三角形算法两种：

• 大津法
  opencv函数：

threshold(gray_src,dst,0,255,cv.THRESH_BINARY | cv.THRESH_OTSU)

• 三角形算法
  opencv函数：

threshold(gray_src,dst,0,255,cv.THRESH_BINARY | cv.THRESH_TRIANGLE)

局部阈值（自适应阈值）

There are two methods for calculating the local threshold：：mean_c 和 guassian_c

• ADAPTIVE_THRESH_MEAN_C
  opencv函数：

adaptiveThreshold(gray_src, dst, 255, cv::ADAPTIVE_THRESH_MEAN_C, cv::THRESH_BINARY, 57, 5);

• ADAPTIVE_THRESH_GAUSSIAN_C
  opencv函数：

adaptiveThreshold(gray_src, dst, cv.ADAPTIVE_THRESH_GAUSSIAN_C, cv.THRESH_BINARY, 25, 10)