用於實現對圖片去噪和灰度化。

package org.eye;

import java.awt.Color;
import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import java.io.File;  
import java.io.IOException;  
import javax.imageio.ImageIO;  

public class ClearImageHelper {
	/**
	 * 
	 * @param sfile
	 *            需要去噪的影象
	 * @param destDir
	 *            去噪後的影象儲存地址
	 * @throws IOException
	 */
	public static void cleanImage(File sfile, String destDir)throws IOException{
		File destF = new File(destDir);
		if (!destF.exists()){
			destF.mkdirs();
		}

		BufferedImage bufferedImage = ImageIO.read(sfile);
		int h = bufferedImage.getHeight();
		int w = bufferedImage.getWidth();

		// 灰度化
		int[][] gray = new int[w][h];
		for (int x = 0; x < w; x++){
			for (int y = 0; y < h; y++){
				int argb = bufferedImage.getRGB(x, y);
				// 影象加亮（調整亮度識別率非常高）
				int r = (int) (((argb >> 16) & 0xFF) * 1.1 + 30);
				int g = (int) (((argb >> 8) & 0xFF) * 1.1 + 30);
				int b = (int) (((argb >> 0) & 0xFF) * 1.1 + 30);
				if (r >= 255){
					r = 255;
				}
				if (g >= 255){
					g = 255;
				}
				if (b >= 255){
					b = 255;
				}
				gray[x][y] = (int) Math.pow((Math.pow(r, 2.2) * 0.2973 + Math.pow(g, 2.2)* 0.6274 + Math.pow(b, 2.2) * 0.0753), 1 / 2.2);
			}
		}

		// 二值化
		int threshold = ostu(gray, w, h);
		BufferedImage binaryBufferedImage = new BufferedImage(w, h,BufferedImage.TYPE_BYTE_BINARY);
		for (int x = 0; x < w; x++){
			for (int y = 0; y < h; y++){
				if (gray[x][y] > threshold){
					gray[x][y] |= 0x00FFFF;
				} else{
					gray[x][y] &= 0xFF0000;
				}
				binaryBufferedImage.setRGB(x, y, gray[x][y]);
			}
		}

		// 矩陣列印
		for (int y = 0; y < h; y++){
			for (int x = 0; x < w; x++){
				if (isBlack(binaryBufferedImage.getRGB(x, y))){
					System.out.print("*");
				} else{
					System.out.print(" ");
				}
			}
			System.out.println();
		}
		ImageIO.write(binaryBufferedImage, "jpg", new File(destDir, sfile.getName()));
	}

	public static boolean isBlack(int colorInt){
		Color color = new Color(colorInt);
		if (color.getRed() + color.getGreen() + color.getBlue() <= 300){
			return true;
		}
		return false;
	}

	public static boolean isWhite(int colorInt){
		Color color = new Color(colorInt);
		if (color.getRed() + color.getGreen() + color.getBlue() > 300){
			return true;
		}
		return false;
	}

	public static int isBlackOrWhite(int colorInt){
		if (getColorBright(colorInt) < 30 || getColorBright(colorInt) > 730){
			return 1;
		}
		return 0;
	}

	public static int getColorBright(int colorInt){
		Color color = new Color(colorInt);
		return color.getRed() + color.getGreen() + color.getBlue();
	}

	public static int ostu(int[][] gray, int w, int h){
		int[] histData = new int[w * h];
		// Calculate histogram
		for (int x = 0; x < w; x++){
			for (int y = 0; y < h; y++){
				int red = 0xFF & gray[x][y];
				histData[red]++;
			}
		}

		// Total number of pixels
		int total = w * h;

		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;
		int threshold = 0;

		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;
			}
		}

		return threshold;
	}
	//圖片灰度，黑白
	public static void gray(String srcImageFile, String destImageFile) {
        try {
            BufferedImage src = ImageIO.read(new File(srcImageFile));
            ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_GRAY);
            ColorConvertOp op = new ColorConvertOp(cs, null);
            src = op.filter(src, null);
            ImageIO.write(src, "JPEG", new File(destImageFile));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
	
	public static void main(String[] args) throws IOException{
		/*File testDataDir = new File("testdata");
		final String destDir = testDataDir.getAbsolutePath()+"/tmp";
		for (File file : testDataDir.listFiles()){
			cleanImage(file, destDir);
		}*/
		File testDataDir = new File("D:\\tmp\\3VG5B.jpg");//去噪
		String destDir ="D:\\tmp\\tmp";
		cleanImage(testDataDir, destDir);
		//gray("D:\\tmp\\3VG5B.jpg","D:\\tmp\\3VG5B1.jpg");//灰度化
	}
}