android bitmap compress
android的照相功能随着手机硬件的发展,变得越来越强大,能够找出很高分辨率的图片。
有些场景中,需要照相并且上传到服务,但是由于图片的大小太大,那么就上传就会很慢(在有些网络情况下),而且很耗流量,要想速度快,那么就需要减小图片的大小。减少图片的大小有两种方法,1. 照小图片; 2. 压缩大图片。 照相时获取小图片一般不太符合要求,因为,图片的清晰度会很差,但是这种情况有个好处就是应用速度会快些; 压缩图片,就是把大图片压缩小,降低图片的质量,在一定范围内,降低图片的大小,并且满足需求(图片仍就清晰)。下面组要是介绍图片的压缩:
1. 照相请查看http://blog.csdn.net/luhuajcdd/article/details/8826587 ->想要保存图片到制定目录,启动Camera应用时,需要指定文件
2. 压缩过程:
2.1 从图片路径中读取图片(图片很大,不能全部加在到内存中处理,要是全部加载到内存中会内存溢出)
- final BitmapFactory.Options options = new BitmapFactory.Options();
- options.inJustDecodeBounds = true;
- BitmapFactory.decodeFile(filePath, options);
- // Calculate inSampleSize
- options.inSampleSize = calculateInSampleSize(options, 480, 800);
- // Decode bitmap with inSampleSize set
- options.inJustDecodeBounds = false;
- Bitmap bm = BitmapFactory.decodeFile(filePath, options);
2.2 处理图片旋转
- int degree = readPictureDegree(filePath);
- bm = rotateBitmap(bm,degree) ;
- private static int readPictureDegree(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;
- }
- private static Bitmap rotateBitmap(Bitmap bitmap, int rotate){
- if(bitmap == null)
- return null ;
- int w = bitmap.getWidth();
- int h = bitmap.getHeight();
- // Setting post rotate to 90
- Matrix mtx = new Matrix();
- mtx.postRotate(rotate);
- return Bitmap.createBitmap(bitmap, 0, 0, w, h, mtx, true);
- }
2.3压缩图片
- bm.compress(Bitmap.CompressFormat.JPEG, 30, baos);//30 是压缩率,表示压缩70%; 如果不压缩是100,表示压缩率为0
完整的方法代码:
- public static Bitmap getSmallBitmap(String filePath) {
- final BitmapFactory.Options options = new BitmapFactory.Options();
- options.inJustDecodeBounds = true;
- BitmapFactory.decodeFile(filePath, options);
- // Calculate inSampleSize
- options.inSampleSize = calculateInSampleSize(options, 480, 800);
- // Decode bitmap with inSampleSize set
- options.inJustDecodeBounds = false;
- Bitmap bm = BitmapFactory.decodeFile(filePath, options);
- if(bm == null){
- return null;
- }
- int degree = readPictureDegree(filePath);
- bm = rotateBitmap(bm,degree) ;
- ByteArrayOutputStream baos = null ;
- try{
- baos = new ByteArrayOutputStream();
- bm.compress(Bitmap.CompressFormat.JPEG, 30, baos);
- }finally{
- try {
- if(baos != null)
- baos.close() ;
- } catch (IOException e) {
- e.printStackTrace();
- }
- }
- return bm ;
- }
- private static int calculateInSampleSize(BitmapFactory.Options options,
- int reqWidth, int reqHeight) {
- // Raw height and width of image
- final int height = options.outHeight;
- final int width = options.outWidth;
- int inSampleSize = 1;
- if (height > reqHeight || width > reqWidth) {
- // Calculate ratios of height and width to requested height and
- // width
- final int heightRatio = Math.round((float) height
- / (float) reqHeight);
- final int widthRatio = Math.round((float) width / (float) reqWidth);
- // Choose the smallest ratio as inSampleSize value, this will
- // guarantee
- // a final image with both dimensions larger than or equal to the
- // requested height and width.
- inSampleSize = heightRatio < widthRatio ? widthRatio : heightRatio;
- }
- return inSampleSize;
- }