Heat map generator of a floor plan image
One way to do this would be:
1) Load in the floor plan image with Matlab or NumPy/matplotlib.
2) Use some built-in edge detection to locate the edge pixels in the floor plan.
3) Form a big list of (x,y) locations where an edge is found in the floor plan.
4) Plot your heat map
5) Scatterplot the points of the floor plan as an overlay.
It sounds like you know how to do each of these steps individually, so all you'll need to do is look up some stuff on how to overlay plots onto the same axis, which is pretty easy in both Matlab and matplotlib.
If you're unfamiliar, the right commands look at are things like meshgrid and surf, possibly contour and their Python equivalents. I think Matlab has a built-in for Canny edge detection. I believe this was more difficult in Python, but if you use the PIL library, the Mahotas library, the scikits.image library, and a few others tailored for image manipulation, it's not too bad. SciPy may actually have an edge filter by now though, so check there first.
The only sticking point will be if your (x,y) data for the temperature are not going to line up with the (x,y) pixel locations in the image. In that case, you'll have to play around with some x-scale factor and y-scale factor to transform your heat map's coordinates into pixel coordinates first, and then plot the heat map, and then the overlay should work.
This is a fairly low-tech way to do it; I assume you just need a quick and dirty plot to illustrate how something's working. This method does have the advantage that you can change the style of the floorplan points easily, making them larger, thicker, thinner, different colors, or transparent, depending on how you want it to interact with the heat map. However, to do this for real, use GIMP, Inkscape, or Photoshop and overlay the heatmap onto the image after the fact.
I want to generate a heat map image of a floor. I have the following things:

A black & white .png image of the floor
A three column array stored in Matlab.
-- The first two columns indicate the X & Y coordinates of the floorpan image
-- The third coordinate denotes the "temperature" of that particular coordinate

I want to generate a heat map of the floor that will show the "temperature" strength in those coordinates. However, I want to display the heat map on top of the floor plan so that the viewers can see which rooms lead to which "temperatures".
Is there any software that does this job? Can I use Matlab or Python to do this?
Thanks,
Nazmul