opencv image conversion from rgb to hsv

Question

When I run this following code on a sample image ie an rgb image; and then execute it to display the converted hsv image, both appear to be different... can anyone explain why? or can you suggest a solution for this not to happen... coz its the same image afterall

Mat img_hsv,img_rgb,red_blob,blue_blob;
img_rgb = imread("pic.png",1);
cvtColor(img_rgb,img_hsv,CV_RGB2HSV);
namedWindow("win1", CV_WINDOW_AUTOSIZE);
imshow("win1", img_hsv);

Answer 1

1. I don't know the new (2.x) OpenCV good enough yet, but usually images loaded in OpenCV are in CV_BGR channel order and not RGB, therefore you most likely want CV_BGR2HSV

2. OpenCV does not actually "know" HSV, it will just encode Hue in first channel, Saturation in second and Value in third. If you display and image in OpenCV, highgui assumes it's a BGR image, thus interpreting the first channel (now Hue) as Blue etc.