Android如何从图片获取二维码

 case CHOOSE_PIC:
          String[] proj = new String[]{MediaStore.Images.Media.DATA};
          Cursor cursor = QRCodeActivity.this.getContentResolver().query(data.getData(), proj, null, null, null);

          if(cursor.moveToFirst()){
            int columnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DATA);
            System.out.println(columnIndex);
            //获取到用户选择的二维码图片的绝对路径
            imgPath = cursor.getString(columnIndex);
          }
          cursor.close();

          //获取解析结果
          Result ret = parseQRcodeBitmap(imgPath);
          if (ret==null){
            Toast.makeText(QRCodeActivity.this,getString(R.string.load_two_dimensional_error), Toast.LENGTH_LONG).show();
          }else {
//            Toast.makeText(QRCodeActivity.this,"解析结果：" + ret.toString(), Toast.LENGTH_LONG).show();
            Intent intent = new Intent();
            intent.putExtra(Intents.Scan.RESULT, ret.toString());
            this.setResult(Activity.RESULT_OK, intent);
            this.overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);
            finish();
          }
          break;

//解析二维码图片,返回结果封装在Result对象中
private com.google.zxing.Result parseQRcodeBitmap(String bitmapPath){
  //解析转换类型UTF-8
  Hashtable hints = new Hashtable();
  hints.put(DecodeHintType.CHARACTER_SET, "utf-8");
  //获取到待解析的图片
  BitmapFactory.Options options = new BitmapFactory.Options();
  //如果我们把inJustDecodeBounds设为true，那么BitmapFactory.decodeFile(String path, Options opt)
  //并不会真的返回一个Bitmap给你，它仅仅会把它的宽，高取回来给你
  options.inJustDecodeBounds = true;
  //此时的bitmap是null，这段代码之后，options.outWidth 和 options.outHeight就是我们想要的宽和高了
  Bitmap bitmap = BitmapFactory.decodeFile(bitmapPath,options);
  //我们现在想取出来的图片的边长（二维码图片是正方形的）设置为400像素
  /**
   options.outHeight = 400;
   options.outWidth = 400;
   options.inJustDecodeBounds = false;
   bitmap = BitmapFactory.decodeFile(bitmapPath, options);
   */
  //以上这种做法，虽然把bitmap限定到了我们要的大小，但是并没有节约内存，如果要节约内存，我们还需要使用inSimpleSize这个属性
  options.inSampleSize = options.outHeight / 400;
  if(options.inSampleSize <= 0){
    options.inSampleSize = 1; //防止其值小于或等于0
  }
  /**
   * 辅助节约内存设置
   *
   * options.inPreferredConfig = Bitmap.Config.ARGB_4444;  // 默认是Bitmap.Config.ARGB_8888
   * options.inPurgeable = true;
   * options.inInputShareable = true;
   */
  options.inJustDecodeBounds = false;
  bitmap = BitmapFactory.decodeFile(bitmapPath, options);
  //新建一个RGBLuminanceSource对象，将bitmap图片传给此对象
  RGBLuminanceSource rgbLuminanceSource = new RGBLuminanceSource(bitmap);
  //将图片转换成二进制图片
  BinaryBitmap binaryBitmap = new BinaryBitmap(new HybridBinarizer(rgbLuminanceSource));
  //初始化解析对象
  QRCodeReader reader = new QRCodeReader();
  //开始解析
  Result result = null;
  try {
    result = reader.decode(binaryBitmap, hints);
  } catch (Exception e) {
    // TODO: handle exception
  }

  return result;
}

//新建一个RGBLuminanceSource对象，将bitmap图片传给此对象
RGBLuminanceSource rgbLuminanceSource = new RGBLuminanceSource(bitmap);
//将图片转换成二进制图片
BinaryBitmap binaryBitmap = new BinaryBitmap(new HybridBinarizer(rgbLuminanceSource));
//初始化解析对象
QRCodeReader reader = new QRCodeReader();

package com.zwcode.p6spro.util;
import java.io.FileNotFoundException;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

import com.google.zxing.LuminanceSource;

public class RGBLuminanceSource extends LuminanceSource {
  private final byte[] luminances;

  public RGBLuminanceSource(Bitmap bitmap) {
    super(bitmap.getWidth(), bitmap.getHeight());
    //得到图片的宽高
    int width = bitmap.getWidth();
    int height = bitmap.getHeight();
    //得到图片的像素
    int[] pixels = new int[width * height];
    //
    bitmap.getPixels(pixels, 0, width, 0, 0, width, height);
    //为了测量纯解码速度,我们将整个图像灰度阵列前面,这是一样的通道
    // YUVLuminanceSource在现实应用。
    //得到像素大小的字节数
    luminances = new byte[width * height];
    //得到图片每点像素颜色
    for (int y = 0; y < height; y++) {
      int offset = y * width;
      for (int x = 0; x < width; x++) {
        int pixel = pixels[offset + x];
        int r = (pixel >> 16) & 0xff;
        int g = (pixel >> 8) & 0xff;
        int b = pixel & 0xff;
        //当某一点三种颜色值相同时，相应字节对应空间赋值为其值
        if (r == g && g == b) {
          luminances[offset + x] = (byte) r;
        }
        //其它情况字节空间对应赋值为：
        else {
          luminances[offset + x] = (byte) ((r + g + g + b) >> 2);
        }
      }
    }
  }

  public RGBLuminanceSource(String path) throws FileNotFoundException {
    this(loadBitmap(path));
  }


  @Override
  public byte[] getMatrix() {
    return luminances;
  }

  @Override
  public byte[] getRow(int arg0, byte[] arg1) {
    if (arg0 < 0 || arg0 >= getHeight()) {
      throw new IllegalArgumentException(
          "Requested row is outside the image: " + arg0);
    }
    int width = getWidth();
    if (arg1 == null || arg1.length < width) {
      arg1 = new byte[width];
    }
    System.arraycopy(luminances, arg0 * width, arg1, 0, width);
    return arg1;
  }

  private static Bitmap loadBitmap(String path) throws FileNotFoundException {
    Bitmap bitmap = BitmapFactory.decodeFile(path);
    if (bitmap == null) {
      throw new FileNotFoundException("Couldn't open " + path);
    }
    return bitmap;
  }
}