This paper presents a new method for the enhancement of colour images containing subsampled chrominance information. The new approach uses a set of carefully designed visual patterns to map a small area of the low resolution signal to a higher resolution grid. The patterns and the mapping procedures are designed in such a way that when the image is expanded, the edge information (orientation and height) and the average intensity within a small area is preserved. The method has been applied to recover full resolution signals from the YC_bC_r9 image format and excellent results have been achieved.