Synthesis of a Colour Texture.

To date most of texture analysis methods have been limited only to grey level images. For instance, a generic MGRF model is usually restricted to 16 grey levels because otherwise model creation and identification become computationally too expensive. A possible approach is to process each channel as a grey-image separately and then to combine the retrieved information [107]. But integrating different colour channels might require computational intensive iterative optimisation procedure. The bunch sampling assumes that texture features are invariant to the colour distribution in an image, so that it converts a colour texture to a grey level image for analysis, i.e. the geometric structure and placement rules of texels are estimated from only the intensity channel of the image. But, at the synthesis stage, the original colour texture is used as a source of texels for sampling. In so doing, colour texels are retrieved and used as construction units to generate a new colour texture. In this case, the synthesis of a colour texture has no much difference from the synthesis of a grey-level one except an extra step needed for converting the training textures from RGB space into grey levels. Since the approach neglects all information preserved in colour channels (hue and saturation), it might fail on certain textures in which texture features are relevant to the distribution of colours. Nevertheless, for most of colour textures used in our experiments, this simple method produces generally good results.