I was trying to display an image and superpose its contours, and noticed that there seems to be a misalignment, or better a scale factor difference, between the contours and the image map. This problem can be seen in a very simple way by using the image_cont routine, for example: a=0*findgen(16,16) a[1,1]=1000 a[12,12]=1000 a[8,8]=1000 a[3,14]=1000 image_cont, a The center of the contour maps are offset with respect to the corresponding pixel. A more careful examination shows that the contours are indeed centered on the integer pixel coordinates in the axis scale (which goes from 0 to 15), but the pixels themselves are not. It looks like the program is trying to squeeze 16 pixels in a 15 pixel-wide frame. This looks wrong to me, and I wonder if there is any bug or in the algorithm that displays the image and/or the one producing and drawing the contours. I'm using IDL 7.0 in a Fedora 8 machine, but it shows up also with v6.4 in a RHEL4 PC. Thanks Nicola Caon