title: OpenCV and reading image with floating point data
body: <p>I use OpenCV to read the image. Then I use Matlab to load the same image.
  Then I display the images. For OpenCV loaded image, the image is has no picture inside and just gray plane. For Matlab loaded image, it has the image what I want.
  The image pixel values are very small floating point data like 0.0021. The code I used to load the image is shown as follow.</p>
  
  <pre><code>`Mat image(IMAGE_ROW, IMAGE_COL, CV_64FC3);
  Mat  gray(IMAGE_ROW, IMAGE_COL, CV_64FC1);
  image = imread(filespath, CV_LOAD_IMAGE_COLOR );// Read the file
  cv::imshow("Image", image);
  cvtColor( image, gray, CV_BGR2GRAY, 1);
  cv::imshow("gray", gray);`
  </code></pre>
  
  <p>Why I can't have the same image as loaded by Matlab?</p>