Perceptual Evaluation of Color-to-Grayscale Image Conversions

Martin Čadík, cadikm@centrum.cz

ABSTRACT

Color images often have to be converted to grayscale for reproduction, artistic purposes, or for subsequent processing. Methods performing the conversion of color images to grayscale aim to retain as much information about the original color image as possible, while simultaneously producing perceptually plausible grayscale results. Recently, many methods of conversion have been proposed, but their performance has not yet been assessed. Therefore, the strengths and weaknesses of color-to-grayscale conversions are not known. In this paper, we present the results of two subjective experiments in which a total of 24 color images were converted to grayscale using seven state-of-the-art conversions and evaluated by 119 human subjects using a paired comparison paradigm. We surveyed nearly 20000 human responses and used them to evaluate the accuracy and preference of the color-to-grayscale conversions. To the best of our knowledge, the study presented in this paper is the first perceptual evaluation of color-to-grayscale conversions. Besides exposing the strengths and weaknesses of the researched methods, the aim of the study is to attain a deeper understanding of the examined field, which can accelerate the progress of color-to-grayscale conversion.

Keywords:

human perception, color to gray conversions, subjective evaluation

ADDITIONAL MATERIALS

[Paper (pdf, 16MB)]
[Presentation slides (pdf, 1.5MB)]
[bibTeX entry (bib)]
[Experimental images (ppm, tif, 25MB)]
[Experimental data (csv)]
[Experimental results (csv)]

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Table: The set of input images and the results of evaluated color to grayscale conversion methods

Image1 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image2 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image3 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image4 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image5 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image6 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image7 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image8 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image9 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image10 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image11 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image12 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image13 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image14 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image15 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image16 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image17 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image18 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image19 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image20 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image21 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image22 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image23 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale

Image24 Accuracy and preference results CIE Y Color2Gray Decolorize Smith08 Rasche05 Bala04 Neumann07
color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale color-to-grayscale


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