Create heat map using Qt

Hello,
I am trying to create heat map to an existing(bitmap or JPG file) using Qt. need the gradient map on top of the image in half transparent form. Is it possible in Qt.
then how I can do this in Qt.
(Eg: I am considering some of the points on an image and the colour values changing from red(val=10) and green(val=0). need a transparent gradient color on top of the image based on this values.)

my advanced thanks to your help..

Look at the Qwt library, specifically the spectrogram object. It contains nearly everything you need to display your heatmap. There is a Qwt sub-forum here for questions, but don't ask: "Give me a complete working program to create a heatmap from a JPG file". You are going to have to learn from the examples.