//直接呼叫getimage,引數為：路徑、寬、高

public static Bitmap getimage(String pathName, int reqWidth, int reqHeight) {
        final BitmapFactory.Options options = new BitmapFactory.Options();
        // 若要對圖片進行壓縮，必須先設定Option的inJustDecodeBounds為true才能進行Option的修改
        options.inJustDecodeBounds = true;
        // 第一次
 
decodeFile是獲取到options.outHeight和options.outWidth
        BitmapFactory.decodeFile(pathName, options);
        // options.inSampleSize是圖片的壓縮比，例如原來大小是100*100，options.inSampleSize為1，則不變，
        // options.inSampleSize為2，則壓縮成50*50
        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
 
        // 重新設定options.inJustDecodeBounds為false，不能修改option
        options.inJustDecodeBounds = false;
        // 根據options重新載入圖片
        Bitmap src = BitmapFactory.decodeFile(pathName, options);
        return src;
    }


    public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int 
 
reqHeight) {

        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            final int halfHeight = height / 2;
            final int halfWidth = width / 2;

            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) > reqHeight
                    && (halfWidth / inSampleSize) > reqWidth) {
                inSampleSize *= 2;
            }
        }
        return inSampleSize;
    }