BitmapFactory.Options压缩图片

BitmapFactory.Options opts = new BitmapFactory.Options();
//只请求图片宽高，不解析图片像素
opts.inJustDecodeBounds = true;
//返回null，获取图片宽高，保存在opts对象中
String path = getExternalCacheDir()+"haha.jpg";
BitmapFactory.decodeFile(path, opts);
//获取图片宽高
int imageWidth = opts.outWidth;
int imageHeight = opts.outHeight;

//获取屏幕宽高
Display dp = getWindowManager().getDefaultDisplay();
int screenWidth = dp.getWidth();
int screenHeight = dp.getHeight();

//计算缩放比例
int scale = 1;
int scaleWidth = imageWidth / screenWidth;
int scaleHeight = imageHeight / screenHeight;

//判断取哪个比例
if(scaleWidth >= scaleHeight && scaleWidth > 1){
    scale = scaleWidth;
}
else if(scaleWidth < scaleHeight && scaleHeight > 1){
    scale = scaleHeight;
}

//设置缩小比例
opts.inSampleSize = scale;
opts.inJustDecodeBounds = false;
//获取缩小后的图片的像素信息
Bitmap bm = BitmapFactory.decodeFile(path, opts);

ImageView iv = (ImageView) findViewById(R.id.iv);
iv.setImageBitmap(bm);