android图像变为黑白

package com.example.clolorfultoblackwhite;

import java.io.FileNotFoundException;
import java.io.IOException;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.media.ThumbnailUtils;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends Activity {
	private Button add;
	private ImageView img;
	private String IMAGE_TYPE = "image/*";
	private int PHOTO = 0;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		add = (Button) findViewById(R.id.button1);
		img = (ImageView) findViewById(R.id.imageView1);
		add.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				// TODO 自动生成的方法存根
				Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
				intent.setType(IMAGE_TYPE);
				startActivityForResult(intent, PHOTO);

			}

		});

	}// /onCreate

	@Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		// TODO 自动生成的方法存根
		// /super.onActivityResult(requestCode, resultCode, data);
		if (resultCode != RESULT_OK) {
			Toast.makeText(MainActivity.this, "返回的结果出错", Toast.LENGTH_SHORT)
					.show();
			return;
		}
		Bitmap bm = null;
		ContentResolver resolver = getContentResolver();
		if (requestCode == PHOTO) {
			Uri originalUri = data.getData();
			try {
				bm = MediaStore.Images.Media.getBitmap(resolver, originalUri);
				bm = convertBlackWhite(bm);
				img.setImageBitmap(bm);

			} catch (FileNotFoundException e) {
				// TODO 自动生成的 catch 块
				e.printStackTrace();
			} catch (IOException e) {
				// TODO 自动生成的 catch 块
				e.printStackTrace();
			}

		}

	}// /onActivityResult

	private Bitmap convertBlackWhite(Bitmap bmp) {
		// TODO 自动生成的方法存根
		int width = bmp.getWidth();
		int height = bmp.getHeight();
		int[] pixels = new int[width * height];
		bmp.getPixels(pixels, 0, width, 0, 0, width, height);
		int alpha = 0xFF << 24;
		for (int i = 0; i < height; i++) {
			for (int j = 0; j < width; j++) {
				int grey = pixels[width * i + j];

				// 分离三原色
				int red = ((grey & 0x00FF0000) >> 16);
				int green = ((grey & 0x0000FF00) >> 8);
				int blue = (grey & 0x000000FF);

				// 转化成灰度像素
				grey = (int) (red * 0.3 + green * 0.59 + blue * 0.11);
				grey = alpha | (grey << 16) | (grey << 8) | grey;
				pixels[width * i + j] = grey;
			}
		}
		// 新建图片
		Bitmap newbmp = Bitmap.createBitmap(width, height, Config.ARGB_8888);
		newbmp.setPixels(pixels, 0, width, 0, 0, width, height);
		Bitmap resizeBmp = ThumbnailUtils.extractThumbnail(newbmp, width,
				height);

		return resizeBmp;
	}

}