给定宽和高计算图片大小的方法

public 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 ? heightRatio : widthRatio ;
    }

    return inSampleSize ;
}