@article{xiong_shamey_2024, title={Psychophysical determination of boundaries and smoothness of color gradients}, volume={41}, ISSN={["1520-8532"]}, url={https://doi.org/10.1364/JOSAA.509530}, DOI={10.1364/JOSAA.509530}, abstractNote={Color gradients constitute an important component in the evaluation of the color quality of multicolored patterns that contain color transitions. A two-part psychophysical study was designed and employed to test the appearance of a set of hue-, chroma-, or lightness-based color gradients. The influence of several parameters on the visual determination of gradients’ boundaries and perceived smoothness was tested. These parameters included gradient type, e.g., transitions based on hue, chroma, lightness or their combination, orientation, slope, and quantization step size of color transitions. The influence of these parameters on intra- and interobserver variability in responses was calculated using the standardized residual sum of squares metric. In the first part of the experiment, the perceived boundaries of color gradient stimuli as well as observer confidence ratings in performing these visual tasks were determined. In the second part, the perceived smoothness ratings of the stimuli and visual confidence ratings in assessments were examined. Four binary color transition images, i.e., brown-green, brown-tan, green-olive, and light sage-olive, were generated. Three different linear-gradient slopes were applied to each transition, and each stimulus was shown to observers, separately, in four orientations: horizontal, vertical, right diagonal, and left diagonal. Results indicate that the gradient slopes influence perceived boundaries and smoothness ratings. When determining smoothness ratings, observers were found to be more tolerant to changes in chroma and lightness than in hue.}, number={3}, journal={JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION}, author={Xiong, Nian and Shamey, Renzo}, year={2024}, month={Mar}, pages={572–580} }
 @article{zhang_xiang_wang_xiong_gao_pan_2020, title={Image retrieval of wool fabric. Part II: based on low-level color features}, volume={90}, ISSN={["1746-7748"]}, DOI={10.1177/0040517519881819}, abstractNote={ Color is difficult to distinguish by human vision and is described by keywords, resulting in low efficiency of wool fabric retrieval in factories at present. To obtain the process sheets of existing products and reduce the work of color measurement in sample analysis, this paper proposes an effective method based on dominant colors (DCs) and color moments (CMs) for wool fabric image retrieval. Firstly, the image was scaled to reduce computational time. Then, the hue, saturation, value color space was divided into 128 parts by the fast color quantization algorithm to extract the DCs of the image. Meanwhile, the CMs based on image partition were calculated in CIE L* a* b* color space to describe the spatial color information. Subsequently, different similarity measure methods were carried out based on the DC feature and CM feature. Finally, experiments were conducted on a wool fabric image database with 20,000 images for parameter optimization and verification. The average precision and recall were up to 87% and 44%, respectively. Experimental results show that the proposed scheme can retrieve images with the same or similar colors quickly and effectively and it outperformed other methods, providing referential assistance for the factory worker when retrieving wool fabrics. }, number={7-8}, journal={TEXTILE RESEARCH JOURNAL}, author={Zhang, Ning and Xiang, Jun and Wang, Lei and Xiong, Nian and Gao, Weidong and Pan, Ruru}, year={2020}, month={Apr}, pages={797–808} }
 @article{li_xiong_wang_pan_gao_zhang_2018, title={An intelligent computer method for automatic mosaic of sequential slub yarn images based on image processing}, volume={88}, ISSN={["1746-7748"]}, DOI={10.1177/0040517517732081}, abstractNote={ In order to analyze the parameters of slub yarn from sequential images accurately, an automatic image mosaic method is proposed in this paper. In this method, a series of overlapping yarn images, which are captured from a moving slub yarn, are stitched into a panorama automatically. Background subtraction, image segmentation and judgment template traversal methods are applied to preprocess the sequential images for obtaining a test image. Subsequently, certain rows in the bottom of the test image are used as a template image to match the next image. The matching coefficient matrix is calculated between the template image and next image based on the normalized cross-correlation method. In the matrix, the coordinates of the peak value are found as the optimal matching points. Two kinds of slub yarn images captured under 40 fps are stitched by using the proposed method and the manual method, respectively. Finally, an objective method is formulated to evaluate the qualities of the image mosaic by the proposed method. The experimental results show that the proposed method can find the match position accurately and is highly consistent with the manual method. }, number={24}, journal={TEXTILE RESEARCH JOURNAL}, author={Li, Zhongjian and Xiong, Nian and Wang, Jingan and Pan, Ruru and Gao, Weidong and Zhang, Ning}, year={2018}, month={Dec}, pages={2854–2866} }
 @article{li_xiong_liu_gao_shamey_2018, title={Determining the colorimetric attributes of multicolored materials based on a global correction and unsupervised image segmentation method}, volume={57}, ISSN={["2155-3165"]}, url={https://doi.org/10.1364/AO.57.007482}, DOI={10.1364/AO.57.007482}, abstractNote={Fast and accurate measurement of colors in multicolored prints using commercial instruments or existing computer vision systems remains a challenge due to limitations in image segmentation methods and the size and complexity of the colored patterns. To determine the colorimetric attributes (L*a*b*) of multicolored materials, an approach based on global color correction and an effective unsupervised image segmentation is presented. The colorimetric attributes of all patches in a ColorChecker chart were measured spectrophotometrically, and an image of the chart was also captured. Images were segmented using a modified Chan-Vese method, and the sRGB values of each patch were extracted and then transformed into L*a*b* values. In order to optimize the transformation process, the performance of 10 models was examined by minimizing the average color differences between measured and calculated colorimetric values. To assess the performance of the model, a set of printed samples was employed and the color differences between the predicted and measured L*a*b* values of samples were compared. The results show that the modified Chan-Vese method, with suitable settings, generates satisfactory segmentation of the printed images with mean and maximum ΔE00 values of 2.43 and 4.28 between measured and calculated values.}, number={26}, journal={APPLIED OPTICS}, author={Li, Zhongjian and Xiong, Nian and Liu, Jiajun and Gao, Weidong and Shamey, Renzo}, year={2018}, month={Sep}, pages={7482–7491} }
 @article{chen_xiong_ge_shamey_2017, title={Characterization of color including temporal hue shift of a range of long-lasting phosphorescent/fluorescent (SiO2/REC@SAOED) composites}, volume={7}, ISSN={["2159-3930"]}, url={https://doi.org/10.1364/OME.7.003909}, DOI={10.1364/ome.7.003909}, abstractNote={A series of luminescent composites was prepared by coating the surface of long-lasting phosphorescent SrAl2O4: Eu2+ ,Dy3+ (SAOED) compounds that emit yellow-greenish light, with various concentrations of red emitting coumarin (REC) fluorescent dye. The color of the luminescent SiO2/REC@SAOED composites, including the temporal hue shift in darkness, was characterized using photoluminescence (PL) emission spectra and spectroradiometric measurements. The PL emission spectra of the pAosphorescent/fluorescent composite contains a continuous band ranging from 450 to 700 nm with two emission peaks. The emission peak for the uncoated SAOED remained invariant, while the fluorescent emission peak exhibited a bathochromic shift from 607 to 618 nm when the concentration of REC in the composite was increased from 0.1 to 0.9 (wt%), indicating that the hue of the luminescent composite would gradually shift towards red with increasing concentrations of coumarin. Although the intensity of the fluorescent peak increased gradually with an increase in the concentration of REC, the ratio of the phosphorescent to fluorescent emission peak intensity also increased gradually over time. Spectroradiometric measurements of compounds showed that the hue of the emitted light from the composites exhibited a gradual hypsochromic (blue) shift over time in darkness, and the extent of the blue-shift decreased gradually with an increase in the concentration of REC.}, number={11}, journal={OPTICAL MATERIALS EXPRESS}, author={Chen, Zhi and Xiong, Nian and Ge, Mingqiao and Shamey, Renzo}, year={2017}, month={Nov}, pages={3909–3918} }