3. Experiments
Experiments were performed to evaluate the similarity of colors on images of fabrics and the real fabrics through a visual comparison task. The participants were exposed to a sequence of the original 138 indigo fabric images which were displayed in the centre of computer screens. Each participant was asked to compare the similarity of e-color and true color of each piece of indigo fabrics. In each test, 138 images were presented one image at a time. Each participant performed the test three times on separate days. The size of image is 512 pixels (width) by 512 pixels (height). There are 5 levels (1,2,3…,5) of similarity scores [13], where 5 indicates the most similarity, and 1 the least similarity. After that the original images were transformed by the power-law transformation to get three copies of each image that are most similar to each of the 138 real fabrics. Then, participants performed similarity evaluations again in the same way as explained above.