日劇看不完

介紹的很詳細，還有附 java code

http://www.labbookpages.co.uk/software/imgProc/otsuThreshold.html

public class OtsuThresholder
{
private int histData[];
private int maxLevelValue;
private int threshold;


public OtsuThresholder()
{
histData = new int[256];
}


public int[] getHistData()
{
return histData;
}


public int getMaxLevelValue()
{
return maxLevelValue;
}


public int getThreshold()
{
return threshold;
}


public int doThreshold(byte[] srcData, byte[] monoData)
{
int ptr;


// Clear histogram data
// Set all values to zero
ptr = 0;
while (ptr < histData.length) histData[ptr++] = 0;


// Calculate histogram and find the level with the max value
// Note: the max level value isn't required by the Otsu method
ptr = 0;
maxLevelValue = 0;
while (ptr < srcData.length)
{
                        /// read the intensity of each pixel and then record
                        /// occur times in the histogram
int h = 0xFF & srcData[ptr];
histData[h] ++;


                        /// record which value is the most occurrence in histogram
if (histData[h] > maxLevelValue) maxLevelValue = histData[h];
ptr ++;
}


// Total number of pixels
int total = srcData.length;


float sum = 0;
for (int t=0 ; t<256 ; t++) sum += t * histData[t];


float sumB = 0;
int wB = 0;
int wF = 0;


float varMax = 0;
threshold = 0;


                /// Calculate intensity from 0-255 to find out the maximum 
for (int t=0 ; t<256 ; t++)
{
wB += histData[t]; // Weight Background
if (wB == 0) continue;


wF = total - wB; // Weight Foreground
if (wF == 0) break;


sumB += (float) (t * histData[t]);


float mB = sumB / wB; // Mean Background
float mF = (sum - sumB) / wF; // Mean Foreground


// Calculate Between Class Variance
float varBetween = (float)wB * (float)wF * (mB - mF) * (mB - mF);


// Check if new maximum found
if (varBetween > varMax) {
varMax = varBetween;
threshold = t;
}
}


// Apply threshold to create binary image
if (monoData != null)
{
ptr = 0;
while (ptr < srcData.length)
{
monoData[ptr] = ((0xFF & srcData[ptr]) >= threshold) ? (byte) 255 : 0;
ptr ++;
}
}


return threshold;
}
}