BitmapFactory.Options

加载和显示图片是很消耗内存的一件事，BitmapFactory.Options 类,  允许我们定义图片以何种方式如何读到内存，

BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
bmpFactoryOptions.inSampleSize = 8;
Bitmap bmp = BitmapFactory.decodeFile(imageFilePath, bmpFactoryOptions);
imv.setImageBitmap(bmp);

上面的代码使图片变成原来的1/8.

	//imv = (ImageView) findViewById(R.id.ReturnedImageView);
			Display currentDisplay = getWindowManager().getDefaultDisplay();
			int dw = currentDisplay.getWidth();
			int dh = currentDisplay.getHeight();
           try
		   {
			BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
			bmpFactoryOptions.inJustDecodeBounds = true;
			Bitmap bmp = BitmapFactory.decodeStream(getContentResolver().
					openInputStream(imageFileUri), null,  bmpFactoryOptions);

			int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)dh);
			int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)dw);

			Log.v("HEIGHRATIO", ""+heightRatio);
			Log.v("WIDTHRATIO", ""+widthRatio);

			if (heightRatio > 1 && widthRatio > 1)
			{
				bmpFactoryOptions.inSampleSize =  heightRatio > widthRatio ? heightRatio:widthRatio;
			}
			bmpFactoryOptions.inJustDecodeBounds = false;
			bmp = BitmapFactory.decodeStream(getContentResolver().
					openInputStream(imageFileUri), null,  bmpFactoryOptions);
            returnedImageView.setImageBitmap(bmp);
		   }
		   catch (FileNotFoundException e)
		   {
			   Log.v("ERROR", e.toString());

		   }

上面的代码让图片根据窗口大小改变

bmpFactoryOptions.inJustDecodeBounds = true;

这一行让代码只解码图片的Bounds