多级阈值。大津的方法 [英] Multi-Level Thresholding. Otsu's Method
问题描述
我知道这个问题是可能的重复多otsu（多阈值）与openCV ，因为它非常相似。但是我没有足够的权限对此发表评论，所以我的问题被回答。
我试图使用OPENCV库使用Otsu的方法做三级电平阈值。我是按照@ Antoni4发布的指南，但它只涵盖两级阈值，我无法将其扩展到三个级别。
我知道如何原始Otsu的方法工作，最大化类方差之间，但我如何可以添加一个外部（或内部）for循环计算第三级阈值我不知道。
我使用此代码进行两级阈值处理：
#includeShadow01-1.cuh
void multiThresh（double& optimalThresh1，double& optimalThresh2，double& optimalThresh3，cv :: Mat& imgHist，cv :: Mat& src）{
double W0K，W1K，W2K ，W3K，M0，M1，M2，M3，currVarB，maxBetweenVar，M0K，M1K，M2K，M3K，
unsigned char * histogram =（unsigned char *）（imgHist.data）;
int N = src.rows * src.cols;
W0K = 0;
W1K = 0;
M0K = 0;
M1K = 0;
MT = 0;
maxBetweenVar = 0;
for（int k = 0; k <= 255; k ++）{
MT + = k *（histogram [k] /（double）N）;
}
for（int t1 = 0; t1 <= 255; t1 ++）
{
W0K + = histogram [t1] // Pi
M0K + = t1 *（histogram [t1] /（double）N）; // i * Pi
M0 = M0K / W0K; //（i * Pi）/ Pi
W1K = 0;
M1K = 0;
for（int t2 = t1 + 1; t2 <= 255; t2 ++）
{
W1K + = histogram [t2] / // Pi
M1K + = t2 *（直方图[t2] /（双）N）; // i * Pi
M1 = M1K / W1K; //（i * Pi）/ Pi
W2K = 1-（W0K + W1K）;
M2K = MT - （M0K + M1K）;
if（W2K <= 0）break;
M2 = M2K / W2K;
currVarB = W0K *（M0-MT）*（M0-MT）+ W1K *（M1-MT）*（M1-MT）+ W2K * ）;
if（maxBetweenVar< currVarB）
{
maxBetweenVar = currVarB;
optimalThresh1 = t1;
optimalThresh2 = t2;
}
}
}
/ p>
我实际上不是这两行：
W2K = 1 - （W0K + W1K）;
M2K = MT - （M0K + M1K）;
如何扩展他们第三个阈值。
提前感谢。
修改@reexre
无关紧要。
我实现了第三个内部for循环来添加另一个阈值级别，并使用以下行作为W3K和M3K，即使我还不知道为什么他们是这样的。
W3K = 1 - （W1K + W2K）;
M3K = MT - （M1K + M2K）;
它可以工作。
，然后：
#includeShadow01-1.cuh
void multiThresh最优Thresh1，double& optimalThresh2，double& optimalThresh3，cv :: Mat& imgHist，cv :: Mat& src）
{
double W0K，W1K，W2K，W3K，M0， M2，M3，currVarB，maxBetweenVar，M0K，M1K，M2K，M3K，MT;
unsigned char * histogram =（unsigned char *）（imgHist.data）;
int N = src.rows * src.cols;
W0K = 0
W1K = 0;
M0K = 0;
M1K = 0;
MT = 0;
maxBetweenVar = 0;
for（int k = 0; k <= 255; k ++）{
MT + = k *（histogram [k] /（double）N）;
}
for（int t1 = 0; t1 <= 255; t1 ++）
{
W0K + = histogram [t1] // Pi
M0K + = t1 *（histogram [t1] /（double）N）; // i * Pi
M0 = M0K / W0K; //（i * Pi）/ Pi
W1K = 0;
M1K = 0;
for（int t2 = t1 + 1; t2 <= 255; t2 ++）
{
W1K + = histogram [t2] / // Pi
M1K + = t2 *（直方图[t2] /（双）N）; // i * Pi
M1 = M1K / W1K; //（i * Pi）/ Pi
W2K = 1-（W0K + W1K）;
M2K = MT - （M0K + M1K）;
if（W2K <= 0）break;
M2 = M2K / W2K;
W2K = 0;
M2K = 0;
for（int t3 = t2 + 1; t3 <= 255; t3 ++）
{
W2K + = histogram [t3] // Pi
M2K + = t3 *（直方图[t3] /（双）N）; // i * Pi
M2 = M2K / W2K; //（i * Pi）/ Pi
W3K = 1-（W0K + W1K + W2K）;
M3K = MT - （M0K + M1K + M2K）;
M3 = M3K / W3K;
currVarB = W0K *（M0-MT）*（M0-MT）+ W1K *（M1-MT）*（M1-MT）+ W2K * （M3-MT）*（M3-MT）;
if（maxBetweenVar< currVarB）
{
maxBetweenVar = currVarB;
optimalThresh1 = t1;
optimalThresh2 = t2;
optimalThresh3 = t3;
}
}
}
}
}
I know this Question is a possible duplicate of Multi otsu(multi-thresholding) with openCV as it's very similar. But I don't have enough privileges to make a comment on that so my question is answered.
I'm trying to do THREE level threshold using Otsu's method using OPENCV library. I was following the guides posted by @Antoni4, but it only covers two-level thresholding and I wasn't able to expand it to three level.
I know how to original Otsu's method works, maximizing the between class variance, but how I could add an external (or internal) for-loop for calculating the third level threshold I did not know.
I'm using this code for the two-level thresholding:
#include "Shadow01-1.cuh"
void multiThresh(double &optimalThresh1, double &optimalThresh2,double &optimalThresh3, cv::Mat &imgHist, cv::Mat &src) {
double W0K, W1K, W2K, W3K, M0, M1, M2, M3, currVarB, maxBetweenVar, M0K, M1K, M2K, M3K, MT;
unsigned char *histogram = (unsigned char*)(imgHist.data);
int N = src.rows*src.cols;
W0K = 0;
W1K = 0;
M0K = 0;
M1K = 0;
MT = 0;
maxBetweenVar = 0;
for (int k = 0; k <= 255; k++) {
MT += k * (histogram[k] / (double) N);
}
for (int t1 = 0; t1 <= 255; t1++)
{
W0K += histogram[t1] / (double) N; //Pi
M0K += t1 * (histogram[t1] / (double) N); //i * Pi
M0 = M0K / W0K; //(i * Pi)/Pi
W1K = 0;
M1K = 0;
for (int t2 = t1 + 1; t2 <= 255; t2++)
{
W1K += histogram[t2] / (double) N; //Pi
M1K += t2 * (histogram[t2] / (double) N); //i * Pi
M1 = M1K / W1K; //(i * Pi)/Pi
W2K = 1 - (W0K + W1K);
M2K = MT - (M0K + M1K);
if (W2K <= 0) break;
M2 = M2K / W2K;
currVarB = W0K * (M0 - MT) * (M0 - MT) + W1K * (M1 - MT) * (M1 - MT) + W2K * (M2 - MT) * (M2 - MT);
if (maxBetweenVar < currVarB)
{
maxBetweenVar = currVarB;
optimalThresh1 = t1;
optimalThresh2 = t2;
}
}
}
}
I actually don't what are those two lines:
W2K = 1 - (W0K + W1K);
M2K = MT - (M0K + M1K);
And how I could expand them for the third threshold.
Thanks in advance.
[Edit] Fixed a bug reported by @reexre Yeah, never mind.
I implemented a third inner for-loop to add another threshold level and used the following lines as the W3K and M3K, even though I still don't know why they are like this.
W3K = 1 - (W1K + W2K);
M3K = MT - (M1K + M2K);
It works.
Whole code is, then:
#include "Shadow01-1.cuh"
void multiThresh(double &optimalThresh1, double &optimalThresh2, double &optimalThresh3, cv::Mat &imgHist, cv::Mat &src)
{
double W0K, W1K, W2K, W3K, M0, M1, M2, M3, currVarB, maxBetweenVar, M0K, M1K, M2K, M3K, MT;
unsigned char *histogram = (unsigned char*)(imgHist.data);
int N = src.rows*src.cols;
W0K = 0;
W1K = 0;
M0K = 0;
M1K = 0;
MT = 0;
maxBetweenVar = 0;
for (int k = 0; k <= 255; k++) {
MT += k * (histogram[k] / (double) N);
}
for (int t1 = 0; t1 <= 255; t1++)
{
W0K += histogram[t1] / (double) N; //Pi
M0K += t1 * (histogram[t1] / (double) N); //i * Pi
M0 = M0K / W0K; //(i * Pi)/Pi
W1K = 0;
M1K = 0;
for (int t2 = t1 + 1; t2 <= 255; t2++)
{
W1K += histogram[t2] / (double) N; //Pi
M1K += t2 * (histogram[t2] / (double) N); //i * Pi
M1 = M1K / W1K; //(i * Pi)/Pi
W2K = 1 - (W0K + W1K);
M2K = MT - (M0K + M1K);
if (W2K <= 0) break;
M2 = M2K / W2K;
W2K = 0;
M2K = 0;
for (int t3 = t2 + 1; t3 <= 255; t3++)
{
W2K += histogram[t3] / (double) N; //Pi
M2K += t3 * (histogram[t3] / (double) N); // i*Pi
M2 = M2K / W2K; //(i*Pi)/Pi
W3K = 1 - (W0K + W1K + W2K);
M3K = MT - (M0K + M1K + M2K);
M3 = M3K / W3K;
currVarB = W0K * (M0 - MT) * (M0 - MT) + W1K * (M1 - MT) * (M1 - MT) + W2K * (M2 - MT) * (M2 - MT) + W3K * (M3 - MT) * (M3 - MT);
if (maxBetweenVar < currVarB)
{
maxBetweenVar = currVarB;
optimalThresh1 = t1;
optimalThresh2 = t2;
optimalThresh3 = t3;
}
}
}
}
}
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