Investigations for Weighting Functions of Color-Difference Formulae Based on Small Suprathreshold Color Differences

Zhehong, 汪哲弘 Wang; Haisong, 徐海松 Xu

doi:10.3788/aos20082806.1215

Cited by 6 publications

(4 citation statements)

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“…The S-CIELAB value expresses the calibration effect, which requires a reference scale to visually demonstrate the reliability of the calibration effect. As perception of light and dark in images involves visual and psychological stimuli, the constant stimulation method [16,17] in psychophysical experiments can be utilized to determine the threshold of human perception or tolerance in the direction of lightness and darkness. For the S-CIELAB threshold evaluation experiment, four sample images from the above-mentioned experiment and four ISO12640-2 image test pictures, namely N1 (Woman), N2 (Flower), N6 (Pier), and S1 (Pot), were selected as constant stimuli.…”

Section: S-cielab Experiments For Human-eye Discrimination Threshold ...mentioning

confidence: 99%

A colour correction method for improperly exposed images

2023

AOPC 2023: Computing Imaging Technology

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Digital images are widely used in daily life and scientific researches, however, due to some uncertain reasons in imaging capture devices the improperly exposure may occur during the operation which can significantly reduce image quality and could terribly destroy the visual sensations or following processing. In order to correct such improperly exposed images, GretagMacbeth Colour Checker DC was used in this study, and via multi-exposure technology we measured the colour features of the multi-level dynamic range of the camera, and then a polynomial model was adopted to set up a 3D colour mapping relationship corresponding to a reference image which can be used as a basis for an image colour correction algorithm. To evaluate the differences between corrected and reference images, the S-CIELAB image difference model was applied that took spatial characters of human visual system into account. Experiment results show that the proposed colour correction method could achieve 2.0~5.5 S-CIELAB units corresponding to reference images. For the purpose of proving the result is acceptable, A visual experiment was designed using the psychophysical method of constant stimuli, and its results showed that the discrimination threshold for visually distinguishing on image differences are around 4.4 S-CIELAB units. This means that the correction method of this study could successfully correct such improperly exposed images to visually nice ones under or around the visual discrimination level.

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Section: S-cielab Experiments For Human-eye Discrimination Threshold ...mentioning

confidence: 99%

A colour correction method for improperly exposed images

2023

AOPC 2023: Computing Imaging Technology

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“…The color difference formula is constantly being improved. McDonald, Witt, RIT-Dupont [27], and others have conducted a series of experiments and collected important data sets for the proposal or prediction of color difference formulas [28][29][30][31]. The CIE DE2000 color difference formula is currently the closest color difference formula to human vision.…”

Section: Introductionmentioning

confidence: 99%

Application of the Entropy Method and Color Difference Formula to the Evaluation of Round Brilliant Cut Diamond Scintillation

Liu

Guo

et al. 2020

Mathematics

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A modeling approach combining the entropy method and color difference formula is proposed in order to quantitatively evaluate diamond scintillation. The images of 66 diamonds were captured from 0° to 105° rotation at 15° intervals. The color difference of corresponding pixels in adjacent rotation angle images was calculated using a MatLab r2014a program, which indicated the diamond’s color change due to its scintillation. A threshold (10) was determined to divide the color difference into seven color difference intervals, the percentage of which indicated the color-change area. The color difference and the percentage were comprehensively analyzed using the entropy method to evaluate diamond scintillation objectively and quantitatively. Lightness was the main factor affecting the diamond scintillation while chroma and hue also significantly affected it.

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“…In the color of the evaluation standard light source, the selection of selecting and formula has a great influence on the results were. In general, nature daylight of 8am to 10am and 3pm to 5pm in china north areas is an ideal illuminant to observe and compare color, so the illuminant D 65 which similar to north areas daylight is selected to reveal synthetic spinel color [2], so this experiment selection of northern sky simulation system means source D65 light for standard light, in order to reflect the true synthetic blue spinels' own color, select the color space basic formula, and with formula CIE LAB, CIE DE2000 [3], this formula calibrated in a certain extent raised visual uniformity [4].…”

Section: Introductionmentioning

confidence: 99%

The Contribution of Co<sup>2+</sup> to Blue Color of Synthetic Spinel

Guo

2011

KEM

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Through to 110 pieces purity transparent and color uniform, 3 x 5 x 7mm blue synthetic spinel made with the flame fusion method on chemical compositions and color parameter measurement the Co2+ content and color changes, clear the influence on Co2+ relationship of blue synthetic spinels’ color appearance. Through LA-ICP-MS to analysis the cause of colorant content, proof that with Co2+, the increase of the content of synthetic spinel will shift blue to purple tone, and C* shows a parabola form with the drop of L*, 700 ppm ~ 900 ppm place in peak. DL* Î (3.55 ~ 76.94) with Co2+ Î (4.59 ppm ~ 1849 ppm) change the largest amount, DC* Î (-9.99 ~ 29.32) next, DH* Î (-20.34 ~ 4.67) compared with before two changes smallest. Co2+ content in 100ppm below, blue color of synthetic spinel with Co2+ content increased changes greatly; 500 ~ 1500 ppm, visually achieve optimal color (C* higher); above 1500ppm, because of the Co2+ overmuch make the color burn cause the overall decline of transparency, the change of L* tends to be gentle, C* decrease obviously. Use Color i5 in standard color measurement instrument lighting source D65, measured the lightness L*, specimen Color a* and b*, chroma C* and tonal angle ho, based on the uniform color space CIE 1976 L*a*b*, in lightness minimum L 9-10 specimen (processing data for standard to 9th), with the help of DE2000 benchmark for calculating formulas, the Color, the color difference train E* by partial correlation analysis card clearly degrees of off color changes L* has certain influence on rDL*×DE*= 0.996, while rDC*×DE*= -0.427, rDH*×DE*= -0.339. Conclusion, the bule color of synthetic spinel because of its Co2+ content changes main influencing L* to contribute to its color appearance.

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Investigations for Weighting Functions of Color-Difference Formulae Based on Small Suprathreshold Color Differences

Cited by 6 publications

References 0 publications

A colour correction method for improperly exposed images

A colour correction method for improperly exposed images

Application of the Entropy Method and Color Difference Formula to the Evaluation of Round Brilliant Cut Diamond Scintillation

The Contribution of Co<sup>2+</sup> to Blue Color of Synthetic Spinel

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