The world we perceive is a colourful world and most of the imaging is also in colour. You will already be familiar with the notion of 3 primary colours, namely, Red, Green and Blue. This is an additive colour model, since any colour can be represented as a weighted sum of the 3 primary colours. When all the three are present in equal proportion then we obtain the white colour. Most imaging devices such as cameras, acquire 3 images (colour planes), one for each of these primary colours. Likewise all display devices use the primary colour model for their input.

In contrast to the above are devices such as printers which use a different set of colours : Cyan, Magenta and Yellow. This is a subtractive model since any colour is created by subtracting weighted combinations of the above 3 colours from white. Thus, to create black colour, we need white- (cyan + magenta + yellow).

The early approach to colour image processing problem focussed on which colour model should be used and if the processing can/should be done on every colour plane. Both these choices affect the result of processing. These approaches treat a colour image as composed of 3 greyscale images, i.e. three images with every pixel being a scalar. This approach has some limitations which you will study in your experiment. The recent trend has been to treat the colour image as an image where every pixel is a 3-D vector.

In this experiment, you will study a) the different colour models and b) the effect of processing colour images by considering them as composed of three colour planes. Specifically, you will experiment and find out the appropriateness of different colour models for enhancement and the effect of processing all or one of the planes of the input image, on the output image.