package com.jotuntech.sketcher.common.filter;

import com.jotuntech.sketcher.common.Pixels;

public class AutoContrastFilter implements Filter {
	int[] alphaHistogram, colorHistogram;
	int alphaBlackPoint, alphaWhitePoint, colorBlackPoint, colorWhitePoint, totalPixels, alphaRange, colorRange;
	float maxBlackFraction, maxWhiteFraction;
	
	public AutoContrastFilter() {
		
	}
	
	public void setSize(int width, int height) { }

	public void setParameterA(float a) {
		maxBlackFraction = a;
	}

	public void setParameterB(float b) {
		maxWhiteFraction = b;
	}

	public void setParameterC(float c) { }

	public boolean isPass1ReadOnly() {
		return true;
	}

	public boolean hasPass2() {
		return true;
	}

	public boolean isPass2Reversed() {
		return false;
	}

	public void startPass1() {
		totalPixels = 0;
		alphaHistogram = new int[256];
		colorHistogram = new int[256];
	}

	public int processPass1Pixel(int pixel) {
		int alpha = Pixels.getChannel0(pixel);
		if(alpha > 0) {
			++alphaHistogram[alpha];
			++colorHistogram[(Pixels.getChannel1(pixel) + (Pixels.getChannel2(pixel) << 1) + Pixels.getChannel3(pixel)) >> 2];
			++totalPixels;
		}
		return pixel;
	}

	public void startPass2() {
		int maxBlackPixels = (int) Math.ceil(maxBlackFraction * totalPixels);
		int maxWhitePixels = (int) Math.ceil(maxWhiteFraction * totalPixels);

		alphaBlackPoint = 0;
		for(int alphaBlackPixels = 0; alphaBlackPixels + alphaHistogram[alphaBlackPoint] <= maxBlackPixels && alphaBlackPoint < alphaHistogram.length; alphaBlackPixels += alphaHistogram[alphaBlackPoint++]) { }
		
		alphaWhitePoint = alphaHistogram.length - 1;
		for(int alphaWhitePixels = 0; alphaWhitePixels + alphaHistogram[alphaWhitePoint] <= maxWhitePixels && alphaWhitePoint >= 0; alphaWhitePixels += alphaHistogram[alphaWhitePoint--]) { }

		System.err.println("alphaBlackPoint = " + alphaBlackPoint);
		System.err.println("alphaWhitePoint = " + alphaWhitePoint);

		alphaRange = alphaWhitePoint - alphaBlackPoint;
		
		if(alphaRange <= 0) {
			alphaBlackPoint = 0;
			alphaWhitePoint = 255;
			alphaRange = 255;
		}

		colorBlackPoint = 0;
		for(int colorBlackPixels = 0; colorBlackPixels + colorHistogram[colorBlackPoint] <= maxBlackPixels && colorBlackPoint < colorHistogram.length; colorBlackPixels += colorHistogram[colorBlackPoint++]) { }

		colorWhitePoint = colorHistogram.length - 1;
		for(int colorWhitePixels = 0; colorWhitePixels + colorHistogram[colorWhitePoint] <= maxWhitePixels && colorWhitePoint >= 0; colorWhitePixels += colorHistogram[colorWhitePoint--]) { }
		
		System.err.println("colorBlackPoint = " + colorBlackPoint);
		System.err.println("colorWhitePoint = " + colorWhitePoint);

		colorRange = colorWhitePoint - colorBlackPoint;
		
		if(colorRange <= 0) {
			colorBlackPoint = 0;
			colorWhitePoint = 255;
			colorRange = 255;
		}
	}

	public int processPass2Pixel(int pixel) {
		int alpha = Math.min(255, Math.max(0, Pixels.getChannel0(pixel) - alphaBlackPoint) * 255 / alphaRange);
		int red = Math.min(255, Math.max(0, Pixels.getChannel1(pixel) - colorBlackPoint) * 255 / colorRange);
		int green = Math.min(255, Math.max(0, Pixels.getChannel2(pixel) - colorBlackPoint) * 255 / colorRange);
		int blue = Math.min(255, Math.max(0, Pixels.getChannel3(pixel) - colorBlackPoint) * 255 / colorRange);
		return Pixels.pack(alpha, red, green, blue);
	}

}