ColorStatistics.java

package ij.process;
import ij.measure.Calibration;

/** RGB image statistics, including histogram. */
public class ColorStatistics extends ImageStatistics {

	/** Construct an ImageStatistics object from a ColorProcessor
		using the standard measurement options (area, mean,
		mode, min and max). */
	public ColorStatistics(ImageProcessor ip) {
		this(ip, AREA+MEAN+MODE+MIN_MAX, null);
	}

	/** Constructs a ColorStatistics object from a ColorProcessor using
		the specified measurement options.
	*/
	public ColorStatistics(ImageProcessor ip, int mOptions, Calibration cal) {
		ColorProcessor cp = (ColorProcessor)ip;
		histogram = cp.getHistogram();
		setup(ip, cal);
		getRawStatistics(0,255);
		if ((mOptions&MIN_MAX)!=0)
			getRawMinAndMax(0,255);
		if ((mOptions&ELLIPSE)!=0 || (mOptions&SHAPE_DESCRIPTORS)!=0)
			fitEllipse(ip, mOptions);
		else if ((mOptions&CENTROID)!=0)
			getCentroid(ip);
		if ((mOptions&(CENTER_OF_MASS|SKEWNESS|KURTOSIS))!=0)
			calculateMoments(ip);
		if ((mOptions&MEDIAN)!=0)
			calculateMedian(histogram, 0, 255, cal);
	}

	void calculateMoments(ImageProcessor ip) {
		byte[] mask = ip.getMaskArray();
		int i, mi;
		double v, v2, sum1=0.0, sum2=0.0, sum3=0.0, sum4=0.0, xsum=0.0, ysum=0.0;
		for (int y=ry,my=0; y<(ry+rh); y++,my++) {
			i = y*width + rx;
			mi = my*rw;
			for (int x=rx; x<(rx+rw); x++) {
				if (mask==null || mask[mi++]!=0) {
					v = ip.getPixelValue(x, y);
						v2 = v*v;
						sum1 += v;
						sum2 += v2;
						sum3 += v*v2;
						sum4 += v2*v2;
						xsum += x*v;
						ysum += y*v;
				}
				i++;
			}
		}
	    double mean2 = mean*mean;
	    double variance = sum2/pixelCount - mean2;
	    double sDeviation = Math.sqrt(variance);
	    skewness = ((sum3 - 3.0*mean*sum2)/pixelCount + 2.0*mean*mean2)/(variance*sDeviation);
	    kurtosis = (((sum4 - 4.0*mean*sum3 + 6.0*mean2*sum2)/pixelCount - 3.0*mean2*mean2)/(variance*variance)-3.0);
		xCenterOfMass = xsum/sum1+0.5;
		yCenterOfMass = ysum/sum1+0.5;
		if (cal!=null) {
			xCenterOfMass = cal.getX(xCenterOfMass);
			yCenterOfMass = cal.getY(yCenterOfMass, height);
		}
	}

}