图片压缩那些事

//判断照片角度
    private final static int getDegress(String path) {
        int degree = 0;
        try {
            ExifInterface exifInterface = new ExifInterface(path);
            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;
    }

    /**
     * rotate the bitmap 
     * @param bitmap
     * @param degress
     * @return
     */
    private static Bitmap rotateBitmap(Bitmap bitmap, int degress) {
        if (bitmap != null) {
            Matrix m = new Matrix();
            m.postRotate(degress); 
            bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), m, true);
            return bitmap;
        }
        return bitmap;
    }

    /**
     * 压缩指定路径图片，并将其保存在缓存目录中，通过isDelSrc判定是否删除源文件，并获取到缓存后的图片路径
     * @param context
     * @param srcPath
     * @param isDelSrc
     * @return
     */
    public final static String compressBitmap(Context context, String srcPath, boolean isDelSrc) {
        Bitmap bitmap = compressImage(srcPath);
        File srcFile = new File(srcPath);
        String desPath = "";
        int degree = getDegress(srcPath);
        try {
            if (degree != 0) bitmap = rotateBitmap(bitmap, degree);
            File file = new File("新路径"+srcFile.getName());
            desPath = file.getPath();
            FileOutputStream  fos = new FileOutputStream(file);
            if(srcPath.toLowerCase().endsWith("png"))
                bitmap.compress(Bitmap.CompressFormat.PNG, 50, fos);//把压缩后的数据存放到baos中
            else
                bitmap.compress(Bitmap.CompressFormat.JPEG, 50, fos);
            fos.close();
            if (isDelSrc) srcFile.deleteOnExit();
        } catch (Exception e) {
            Log.e("BitmapHelper-->compressBitmap", e.getMessage()+"");
        }
        return desPath;
    }

    /**
     * 基于质量的压缩算法， 此方法未 解决压缩后图像失真问题
     * <br> 可先调用比例压缩适当压缩图片后，再调用此方法可解决上述问题
     * @param bts
     * @param maxBytes 压缩后的图像最大大小 单位为byte
     * @return
     */
    public final static Bitmap compressImage(Bitmap image, long maxBytes) {
        try {
            int options = 100;
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            image.compress(Bitmap.CompressFormat.JPEG, options, 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
            while ( baos.toByteArray().length/1024 > maxBytes) {//循环判断如果压缩后图片是否大maxByteskb,大于继续压缩
                baos.reset();//重置baos即清空baos
                options -= 10;//每次都减少10
                image.compress(Bitmap.CompressFormat.JPEG, options, baos);//这里压缩options%，把压缩后的数据存放到baos中
            }
            byte[] bts = baos.toByteArray();
            Bitmap bmp = BitmapFactory.decodeByteArray(bts, 0, bts.length);
            return bmp;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
    /**
     * 按照图片的比例进行压缩
     * @param srcPath
     * @return
     */
    public final static Bitmap compressImage(String srcPath) {
        BitmapFactory.Options newOpts = new BitmapFactory.Options();
        //开始读入图片，此时把options.inJustDecodeBounds 设回true了
        newOpts.inJustDecodeBounds = true;
        Bitmap bitmap = BitmapFactory.decodeFile(srcPath,newOpts);
        newOpts.inJustDecodeBounds = false;
        int w = newOpts.outWidth;
        int h = newOpts.outHeight;
        float reqHeight = 800f;//这里设置高度为800f
        float reqWidth = 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 inSampleSize = 1;
        if (h > reqHeight || w > reqWidth) {
            final int heightRatio = Math.round((float) h/ (float) reqHeight);
            final int widthRatio = Math.round((float) w / (float) reqWidth);
            inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
        }
        if (inSampleSize <= 0)
            inSampleSize = 1;
        newOpts.inSampleSize = inSampleSize;//设置缩放比例
        //重新读入图片，注意此时已经把options.inJustDecodeBounds 设回false了
        bitmap = BitmapFactory.decodeFile(srcPath, newOpts);
        if(bitmap != null && !srcPath.toLowerCase().endsWith("png"))//png格式的图片不能进行质量压缩
            bitmap = compressImage(bitmap,100);//压缩好比例大小后再进行质量压缩
        return bitmap;
    }