Controlling Color in Displays: A discussion on Quality Jean-Baptiste Thomas Centre de Recherche et de Restauration des musées de France CNRS UMR 171 Jean-Baptiste THOMAS, 1
V D65 (λ) AcquisitionReproduction Technology, Model and Quality Direct view Transfer via a network, storage, compression, etc. I. Color management Jean-Baptiste THOMAS, 2 09/06/2010
I. Color management Jean-Baptiste THOMAS, D s fc D s fc V D65 (λ) COLOR PCS CIEXYZ CIELAB … RGB 3 Color management 09/06/2010
I. Color management Jean-Baptiste THOMAS, D s fc D s fc V D65 (λ) COLOR PCS CIEXYZ CIELAB … RGB 4 Color management 09/06/2010
Technology Gamut mappingModel II. Displays Jean-Baptiste THOMAS, 5 Quality 09/06/2010
II. Displays Jean-Baptiste THOMAS, 6 Colorimetric characterization RGBCIELAB Forward model CIEXYZ = F(RGB) CIELAB = F(RGB) Inverse model RGB = F -1 (CIELAB) 09/06/2010
II. Displays Jean-Baptiste THOMAS, 7 Quality estimation CIELAB 1 DISPLAY MODEL MEASURE RGB DISPLAY WHITE XYZ 1 CIELAB 2 METRIC XYZ 2 09/06/2010
III. Quality Jean-Baptiste THOMAS, 8 Quality estimation Metrics o CIELAB color space Quality criterion (colorimetry) o Just noticeable difference: Kang (97), Mahy et al (94) Quality criterion (Color imaging) o Rules of thumb: Hardeberg (99), Abrardo et al (96) o Perceptability acceptance for pictorial images: Stokes et al (92), Catrysse et al (99), Gibson and Fairchild (00) 09/06/2010
III. Quality Jean-Baptiste THOMAS, 9 Need Professional o THE COLOR RENDERING HAS TO BE PERFECTLY ACCURATE Consumer o AESTHETIC AND INTENDED MEANING HAVE TO BE PRESERVED 09/06/2010
III. Quality Jean-Baptiste THOMAS, 10 Need Want to ask for more funding ? I am a good worker, Give me more money! CONSUMER: AESTHETIC AND INTENDED MEANING HAVE TO BE PRESERVED 09/06/2010
III. Quality Jean-Baptiste THOMAS, 11 Need Get more work! I am a good worker, Give me more money! CONSUMER: AESTHETIC AND INTENDED MEANING HAVE TO BE PRESERVED 09/06/2010
III. Quality Jean-Baptiste THOMAS, 12 Need PROFESSIONAL: THE COLOR RENDERING HAS TO BE PERFECTLY ACCURATE Color rendering of multi-spectral images of art paintings under different illuminants (Image: C2RMF) 09/06/2010
III. Quality Jean-Baptiste THOMAS, 13 Set of thresholds Compilation of previous works adapted to the need Nothing more than a rule of thumb 09/06/2010
III. Quality Jean-Baptiste THOMAS, 14 Models classification PLVCBalaPLCC*Polyharmonic splines GOGO 54 (XYZ) measures 1 to 3 visual tasks times 1 to 3 pictures 54 (Y) measures 3 (XYZ) 216 (XYZ) measures 4 to 54 (Y) measures 3 (XYZ) Technology dependent Technology independent CRT Professional or Consumer ConsumerProfessional or Consumer ProfessionalConsumer The efficiency of a model is dependent on several factors: the number of measurements, the nature of the data to measure, the computational cost, its accuracy, etc. It depends strongly on the display 09/06/2010
III. Quality Jean-Baptiste THOMAS, 15 Global quality of a system ? Technology: spatial, temporal Gamut mappingInverse model 09/06/2010
Jean-Baptiste THOMAS, 16 MODEL -1 CIELAB RGB 1 DISPLAY WHITE XYZ 1 METRIC XYZ 2 RGB 2 Evaluation of the model inversion Global quality of a system ? 09/06/2010 MODEL III. Quality
Jean-Baptiste THOMAS, 17 MODEL -1 CIELAB DISPLAYMEASURERGB 1 DISPLAY WHITE XYZ 1 METRIC XYZ 2 RGB 2 Evaluation of the inverse model Global quality of a system ? 09/06/2010 III. Quality
Jean-Baptiste THOMAS, 18 MODEL -1 CIELAB 1 DISPLAYMEASURE RGB DISPLAY WHITE XYZ 1 CIELAB 2 METRIC XYZ 2 Perceptual evaluation of the inverse model Global quality of a system ? 09/06/2010 III. Quality
Jean-Baptiste THOMAS, 19 Spatial difference in lightness and chroma Global quality of a system ? 09/06/2010
III. Quality Jean-Baptiste THOMAS, 20 A illuminationD65 illumination Colors out of gamut Global quality of a system ? Gamut mapping 09/06/2010
III. Quality Jean-Baptiste THOMAS, 21 Global quality of a system ? Technology: spatial, temporal Gamut mappingInverse model 09/06/2010
III. Quality Jean-Baptiste THOMAS, 22 Global quality of a system ? NO INFORMATION ON ACTUAL QUALITY 09/06/2010
IV. This is almost the end Jean-Baptiste THOMAS, 23 So what? Required accuracy depends on the need o No opposition with constraints Model quality ≠ Color reproduction quality o Depending on purpose Spatial issue o Colorimetry and color management are point wise Psycho-physical evaluation is difficult and expensive 09/06/2010
IV. This is almost the end Jean-Baptiste THOMAS, 24 The worst thing IT IS IMAGE DEPENDENT 09/06/2010
IV. This is the end, beautiful friend Jean-Baptiste THOMAS, 25 CHOOSE WHAT YOU WANT TO BE: Be silly: Try to find a solution Be pragmatic: Pretend it is OK like this Be wise: Change research interest Be lazy: Go to fish 09/06/2010