使用@blackapps评论和使用@ariefbayu从这篇文章https://stackoverflow.com/a/8268593/的答案解决了问题

Bitmap scaledBitmap = scaleDown(realImage, MAX_IMAGE_SIZE, true);

public static Bitmap scaleDown(Bitmap realImage, float maxImageSize,
        boolean filter) {
    float ratio = Math.min(
            (float) maxImageSize / realImage.getWidth(),
            (float) maxImageSize / realImage.getHeight());
    int width = Math.round((float) ratio * realImage.getWidth());
    int height = Math.round((float) ratio * realImage.getHeight());

    Bitmap newBitmap = Bitmap.createScaledBitmap(realImage, width,
            height, filter);
    return newBitmap;
}

现在起作用了！