convert to grayscale when loading file
<p>Does thsese two code examples do the same?</p>

<h1>A</h1>

<pre><code>cv::Mat gray = cv::imread(input, CV_LOAD_IMAGE_GRAYSCALE);
</code></pre>

<h1>B</h1>

<pre><code>cv::Mat src = cv::imread(input);
cv::Mat gray;
cv::cvtColor(src, gray, CV_BGR2GRAY);
</code></pre>