## 3 Materials  
We based our experiments on 23 datasets of colour texture images (Section 3.1) arranged into 46 different experimental conditions (Section 3.2). We subdivided the datasets into ten different groups (Sections 3.2.1-3.2.10) based on the following two properties of the images contained therein (see also Table 1 and Figures 1- 10):  
1. The stationariness of the textures;
2. The presence/absence and/or the type of variation in the imaging conditions.  
Property (a) refers to the concept of _stationariness_ as defined in [19], i.e., a texture that \"fills up the whole image and its local statistical properties are the same everywhere in it\". In this case, the subdivision is binary, which means we can have either _stationary_ or _non-station  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **None** & **Illumination** & **Rotation** & **Scale** & **Multiple variations** \\ \hline  & **Group 1** & **Group 3** & **Group 5** & **Group 7** & **Group 9** \\ \hline  & ALOT-95-S-N & ALOT-95-S-I & ALOT-95-S-R & KTH-TIPS-10-S-S & CUREf-61-S-M \\  & CBT-99-S-N & Outex-192-S-I & Kylberg-Sintom-25-S-R & KTH-TIPS2b-11-S-S & Fabrics-1968-S-M \\  & Drexel-18-S-N & RawFood-68-S1 & MondialMarmi-25-S-R & Outex-192-S-S & KTH-TIPS-10-S-M \\  & Kylberg-Sintom-25-S & RawFood-68-S-I2 & Outex-192-S-R & KTH-TIPS2b-11-S-M \\  & MBT-120-S-N & RawFood-68-S-I3 & & LMT-94-S-M \\  & MondialMarmi-25-S-N & & & RDAD-27-S-M \\  & Outex-192-S-N & & & \\  & Parquet-38-S-N & & & \\  & PlantLeaves-20-S-N & & & \\  & RawFood-68-S-N & & & \\  & STeX-20-25-N & & & \\  & USPTex-137-S-N & & & \\  & VisTex-89-S-N & & & \\  & VxC\_TSG-42-S-N & & & \\ \hline  & **Group 2** & **Group 4** & **Group 6** & **Group 8** & **Group 10** \\ \hline  & ALOT-40-NS-N & ALOT-40-NS-I & ALOT-40-NS-R & Outex-59-NS-S & DTD-47-NS-M \\  & ForestSpeces-112-NS-N & Outex-59-NS-I & Outex-59-NS-R & & \\  & MBT-34-NS-N & & & \\  & NewBarkTex-6-NS-N & & & \\  & Outex-59-NS-N & & & \\  & STeX-138-NS-N & & & \\  & USPTex-33-NS-N & & & \\  & VisTex-78-NS-N & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Round-up table of the image datasets used in the experiments. ALOT, Amsterdam Library of Textures; CUREf, Columbia-Utrecht Reflectance and Texture Database; CBT, Coloured Brodatz Textures; MBT, Multiband Texture Database; RawFooT, Raw Food Texture Database; VisTex, Vision Texture Database; RDAD, Robotics Domain Attribute Database; STeX, Salzburg Texture Image Database; DTD, Describable Texture Dataset; S, Stationary; NS, Non-Stationary; N, No variations; I, variations in Illumination; R, variations in Rotation; S, variations in Scale, M, Multiple variations.  
(b) signals whether the samples of a given class have been acquired under steady or variable imaging conditions in terms of illumination, rotation, scale and/or viewpoint. In the remainder, we use the following naming convention to indicate the dataset used:  
<source>-<no.-of-classes>-<prop-a>-<prop-b>  
where:  
* <source> indicates the name of the source dataset the images come from (e.g., Amsterdam Library of Textures (ALOT), KTH-TIPS, etc. as detailed in Section 3.1);
* <no.-of-classes> the number of the colour texture classes in the dataset;
* <prop-a> the stationariness of the textures, which can be either S or NS respectively indicating _Stationary_ and _Non-stationary_ textures;
* <prop-b> the presence/absence and/or the type of intra-class variation in the imaging conditions. This can be either N, I, R, S or M, respectively indicating No variations (steady imaging conditions), variations in _Illumination_, variations in _Rotation_, variations in _Scale_ and _Multiple variations_ (i.e., combined changes in illumination, scale, rotation and/or viewpoint).