Objective automatic assessment of pilling in fabrics by image analysis

A fully automatic method for pilling evaluation in fabrics, previously deve loped from the analysis of Zweigle standard images, is completed for its ap plication to the assessment of real samples. Several aspects are dealt with . As regards the acquisition of input images, a set of primary images seque ntially captured under near-tangential illumination from different sides is proposed to obtain complete information of the pill area along with a good pill-to-background contrast. The significant information for the set is co ncentrated in a single image using the Karhunen-Loeve transform in a later stage of the algorithm. After segmentation, pills appear segmented from the background, and binary noise is reduced by applying a threshold of minimum pill area. This threshold is scale independent when it is expressed in ter ms of the fabric's thread crossings. From the final segmented binary image, two pill features are measured: the total area of pilling, from which the degree of pilling is assigned, and the pill density. The complete method is applied to 32 real samples, which constitute a wide variety of cases. Thre e laboratories with their respective panels of experts for visual rating ar e involved in the assessment of the samples. The results obtained by the im age-analysis method and by the visual raters are compared. Finally, the rob ustness of the method against slight changes in some parameters of the algo rithm is evaluated and compared with the degree of agreement of experts. (C ) 2000 Society of Photo-Optical Instrumentation Engineers.