opencv 阈值分割函数

CV_EXPORTS_W double threshold( InputArray src, OutputArray dst,
double thresh, double maxval, int type );

/**

@brief 对数组的每个元素应用固定阈值处理该函数对多通道数组执行固定阈值分割，常用于从灰度图像生成二值图像（也可使用#compare实现类似功能），或通过过滤过小/过大的像素值来去除噪声。函数支持多种阈值分割类型，由type参数指定。特殊值#THRESH_OTSU或#THRESH_TRIANGLE可与其他类型组合使用。此时函数将采用大津算法或三角算法自动确定最优阈值，并忽略手动指定的thresh值。@注意 目前大津法和三角法仅支持8位单通道图像。@param src 输入数组（多通道，8位或32位浮点类型）@param dst 输出数组（与src尺寸、类型及通道数相同）@param thresh 阈值@param maxval 与#THRESH_BINARY和#THRESH_BINARY_INV类型搭配使用的最大值@param type 阈值分割类型（参见#ThresholdTypes枚举）@return 若使用大津法或三角法，返回计算得到的阈值@另见 adaptiveThreshold, findContours, compare, min, max
*/

THRESH_BINARY 或 THRESH_BINARY_INV，会将大于thresh的像素值设置为maxval，其余设置为0(二值化）
/** Threshold types */
enum
{
CV_THRESH_BINARY =0, /< value = value > threshold ? max_value : 0 */
CV_THRESH_BINARY_INV =1, /< value = value > threshold ? 0 : max_value */
CV_THRESH_TRUNC =2, /< value = value > threshold ? threshold : value */
CV_THRESH_TOZERO =3, /< value = value > threshold ? value : 0 /
CV_THRESH_TOZERO_INV =4, /< value = value > threshold ? 0 : value */
CV_THRESH_MASK =7,
CV_THRESH_OTSU =8, /< use Otsu algorithm to choose the optimal threshold value;
combine the flag with one of the above CV_THRESH_ values /
CV_THRESH_TRIANGLE =16 /**< use Triangle algorithm to choose the optimal threshold value;
combine the flag with one of the above CV_THRESH_ values, but not
with CV_THRESH_OTSU */
};