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