详解android通过uri获取bitmap图片并压缩

Uri mImageCaptureUri = data.getData();
Bitmap photoBmp = null;
if (mImageCaptureUri != null) {
  photoBmp = MediaStore.Images.Media.getBitmap(ac.getContentResolver(), mImageCaptureUri);
}

public static final Bitmap getBitmap(ContentResolver cr, Uri url)
    throws FileNotFoundException, IOException {
  InputStream input = cr.openInputStream(url);
  Bitmap bitmap = BitmapFactory.decodeStream(input);
  input.close();
  return bitmap;
}

Uri mImageCaptureUri = data.getData();
 
Bitmap photoBmp = null;
 
if (mImageCaptureUri != null) {
 
photoBmp = getBitmapFormUri(ac, mImageCaptureUri);
 
}

/**
   * 通过uri获取图片并进行压缩
   *
   * @param uri
   */
  public static Bitmap getBitmapFormUri(Activity ac, Uri uri) throws FileNotFoundException, IOException {
    InputStream input = ac.getContentResolver().openInputStream(uri);
    BitmapFactory.Options onlyBoundsOptions = new BitmapFactory.Options();
    onlyBoundsOptions.inJustDecodeBounds = true;
    onlyBoundsOptions.inDither = true;//optional
    onlyBoundsOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;//optional
    BitmapFactory.decodeStream(input, null, onlyBoundsOptions);
    input.close();
    int originalWidth = onlyBoundsOptions.outWidth;
    int originalHeight = onlyBoundsOptions.outHeight;
    if ((originalWidth == -1) || (originalHeight == -1))
      return null;
    //图片分辨率以480x800为标准
    float hh = 800f;//这里设置高度为800f
    float ww = 480f;//这里设置宽度为480f
    //缩放比。由于是固定比例缩放，只用高或者宽其中一个数据进行计算即可
    int be = 1;//be=1表示不缩放
    if (originalWidth > originalHeight && originalWidth > ww) {//如果宽度大的话根据宽度固定大小缩放
      be = (int) (originalWidth / ww);
    } else if (originalWidth < originalHeight && originalHeight > hh) {//如果高度高的话根据宽度固定大小缩放
      be = (int) (originalHeight / hh);
    }
    if (be <= 0)
      be = 1;
    //比例压缩
    BitmapFactory.Options bitmapOptions = new BitmapFactory.Options();
    bitmapOptions.inSampleSize = be;//设置缩放比例
    bitmapOptions.inDither = true;//optional
    bitmapOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;//optional
    input = ac.getContentResolver().openInputStream(uri);
    Bitmap bitmap = BitmapFactory.decodeStream(input, null, bitmapOptions);
    input.close();
 
    return compressImage(bitmap);//再进行质量压缩
  }
 

/**
  * 质量压缩方法
  *
  * @param image
  * @return
  */
  public static Bitmap compressImage(Bitmap image) {
 
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    image.compress(Bitmap.CompressFormat.JPEG, 100, baos);//质量压缩方法，这里100表示不压缩，把压缩后的数据存放到baos中
    int options = 100;
    while (baos.toByteArray().length / 1024 > 100) { //循环判断如果压缩后图片是否大于100kb,大于继续压缩
      baos.reset();//重置baos即清空baos
      //第一个参数 ：图片格式 ，第二个参数： 图片质量，100为最高，0为最差 ，第三个参数：保存压缩后的数据的流
      image.compress(Bitmap.CompressFormat.JPEG, options, baos);//这里压缩options%，把压缩后的数据存放到baos中
      options -= 10;//每次都减少10
    }
    ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());//把压缩后的数据baos存放到ByteArrayInputStream中
    Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);//把ByteArrayInputStream数据生成图片
    return bitmap;
  }

Uri originalUri = null;
   File file = null;
   if (null != data && data.getData() != null) {
     originalUri = data.getData();
     file = getFileFromMediaUri(ac, originalUri);
   }
 Bitmap photoBmp = getBitmapFormUri(ac, Uri.fromFile(file));
 int degree = getBitmapDegree(file.getAbsolutePath());
 /**
  * 把图片旋转为正的方向
  */
 Bitmap newbitmap = rotateBitmapByDegree(photoBmp, degree);

/**
   * 通过Uri获取文件
   * @param ac
   * @param uri
   * @return
   */
  public static File getFileFromMediaUri(Context ac, Uri uri) {
    if(uri.getScheme().toString().compareTo("content") == 0){
      ContentResolver cr = ac.getContentResolver();
      Cursor cursor = cr.query(uri, null, null, null, null);// 根据Uri从数据库中找
      if (cursor != null) {
        cursor.moveToFirst();
        String filePath = cursor.getString(cursor.getColumnIndex("_data"));// 获取图片路径
        cursor.close();
        if (filePath != null) {
          return new File(filePath);
        }
      }
    }else if(uri.getScheme().toString().compareTo("file") == 0){
      return new File(uri.toString().replace("file://",""));
    }
      return null;
    }

/**
   * 读取图片的旋转的角度
   *
   * @param path 图片绝对路径
   * @return 图片的旋转角度
   */
  public static int getBitmapDegree(String path) {
    int degree = 0;
    try {
      // 从指定路径下读取图片，并获取其EXIF信息
      ExifInterface exifInterface = new ExifInterface(path);
      // 获取图片的旋转信息
      int orientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION,
          ExifInterface.ORIENTATION_NORMAL);
      switch (orientation) {
        case ExifInterface.ORIENTATION_ROTATE_90:
          degree = 90;
          break;
        case ExifInterface.ORIENTATION_ROTATE_180:
          degree = 180;
          break;
        case ExifInterface.ORIENTATION_ROTATE_270:
          degree = 270;
          break;
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
    return degree;
  }

/**
   * 将图片按照某个角度进行旋转
   *
   * @param bm   需要旋转的图片
   * @param degree 旋转角度
   * @return 旋转后的图片
   */
  public static Bitmap rotateBitmapByDegree(Bitmap bm, int degree) {
    Bitmap returnBm = null;
 
    // 根据旋转角度，生成旋转矩阵
    Matrix matrix = new Matrix();
    matrix.postRotate(degree);
    try {
      // 将原始图片按照旋转矩阵进行旋转，并得到新的图片
      returnBm = Bitmap.createBitmap(bm, 0, 0, bm.getWidth(), bm.getHeight(), matrix, true);
    } catch (OutOfMemoryError e) {
    }
    if (returnBm == null) {
      returnBm = bm;
    }
    if (bm != returnBm) {
      bm.recycle();
    }
    return returnBm;
  }