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Diffstat (limited to 'xicc/cam97s3.h')
| -rw-r--r-- | xicc/cam97s3.h | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/xicc/cam97s3.h b/xicc/cam97s3.h new file mode 100644 index 0000000..9893ea4 --- /dev/null +++ b/xicc/cam97s3.h @@ -0,0 +1,169 @@ + +/* + * cam97s3 + * + * Color Appearance Model, based on + * CIECAM97, "Revision for Practical Applications" + * by Mark D. Fairchild, with the addition of the Viewing Flare + * model described on page 487 of "Digital Color Management", + * by Edward Giorgianni and Thomas Madden, and the + * Helmholtz-Kohlraush effect, using the equation + * the Bradford-Hunt 96C model as detailed in Mark Fairchilds + * book "Color Appearance Models". + * + * Author: Graeme W. Gill + * Date: 5/10/00 + * Version: 1.20 + * + * Copyright 2000 Graeme W. Gill + * Please refer to COPYRIGHT file for details. + * This material is licenced under the GNU AFFERO GENERAL PUBLIC LICENSE Version 3 :- + * see the License.txt file for licencing details. + */ + +/* Algorithm tweaks */ +#define CIECAM97S3_SPLINE_E /* Use spline interpolation for eccentricity factor */ + +/* Definitions assumed here: + + Stimulus field is the 2 degrees field of view of the sample + being characterised. + + Viewing/Scene/Image field is the area of the whole image or + display surface that the stimulus is part of. + + Background field is 10-12 degree field surrounding the stimulus field. + This may be within, overlap or encompass the Viewing/Scene/Image field. + + Surround/Adapting field is the visual field minus the background field. + + Visual field is the 130 degree angular field that is seen by the eyes. + + Illuminating field is the field that illuminates the reflective + Scene/Image. It may be the same as the Ambient field. + + Ambient field is the whole surrounding environmental light field. + + NOTE: In "Digital Color Management", Giorgianni and Madden use the term + "Surround" to mean the same thing as "Background" in the CIECAM97 terminology. + The ICC standard doesn't define what it means by "Surround illumination". + +*/ + +/* Rules of Thumb: */ +/* Ambient Luminance (Lat, cd/m^2) is Ambient Illuminance (Lux) divided by PI. */ +/* i.e. Lat = Iat/PI */ /* (1 foot candle = 0.0929 lux) */ + +/* The Adapting/Surround Luminance is often taken to be */ +/* the 20% of the Ambient Luminance. (gray world) */ +/* i.e. La = Lat/5 = Iat/15.7 */ + +/* For a reflective print, the Viewing/Scene/Image luminance (Lv, cd/m^2), */ +/* will be the Illuminating Luminance (Li, cd/m^2) reflected by the */ +/* media white point (Yw) */ + +/* If there is no special illumination for a reflective print, */ +/* then the Illuminating Luminance (Li) will be the Ambient Luminance (Lat) */ + +/* An emisive display will have an independently determined Lv. */ + +/* The classification of the type of surround is */ +/* determined by comparing the Adapting/Surround luminance (La, cd/m^2) */ +/* with the average luminance of the Viewing/Scene/Image field (Lv, cd/m^2) */ + +/* La/Lv == 0%, dark */ +/* La/Lv 0 - 20%, dim */ +/* La/Lv > 20%, average */ +/* special, cut sheet */ + +/* The Background relative luminance Yb is typically assumed to */ +/* be 0.18 .. 0.2, and is assumed to be grey. */ + +/* The source of flare light depends on the type of display system. */ +/* For a CRT, it will be the Ambient light reflecting off the glass surface. */ +/* (This implies Yf = Lat * reflectance/Lv) */ +/* For a reflection print, it will be the Illuminant reflecting from the media */ +/* surface. (Yf = Li * reflectance) */ +/* For a projected image, it will be stray projector light, scattered by the */ +/* surround, screen and air particles. (Yf = Li * reflectance_and_scattering) */ + +/* + + Typical Ambient Illuminance brightness + (Lux) La Condition + 11 1 Twilight + 32 2 Subdued indoor lighting + 64 4 Less than typical office light; sometimes recommended for + display-only workplaces (sRGB) + 350 22 Typical Office (sRGB annex D) + 500 32 Practical print evaluationa (ISO-3664 P2) + 1000 64 Good Print evaluation (CIE 116-1995) + 1000 64 Overcast Outdoors + 2000 127 Critical print evaluation (ISO-3664 P1) + 10000 637 Typical outdoors, full daylight + 50000 3185 Bright summers day + +*/ + +/* ---------------------------------- */ +struct _cam97s3 { +/* Public: */ + void (*del)(struct _cam97s3 *s); /* We're done with it */ + + int (*set_view)( + struct _cam97s3 *s, + ViewingCondition Ev, /* Enumerated Viewing Condition */ + double Wxyz[3], /* Reference/Adapted White XYZ (Y scale 1.0) */ + double La, /* Adapting/Surround Luminance cd/m^2 */ + double Yb, /* Luminance of Background relative to reference white (range 0.0 .. 1.0) */ + double Lv, /* Luminance of white in the Viewing/Scene/Image field (cd/m^2) */ + /* Ignored if Ev is set */ + double Yf, /* Flare as a fraction of the reference white (range 0.0 .. 1.0) */ + double Fxyz[3], /* The Flare white coordinates (typically the Ambient color) */ + int hk /* Flag, NZ to use Helmholtz-Kohlraush effect */ + ); + + /* Conversions */ + int (*XYZ_to_cam)(struct _cam97s3 *s, double *out, double *in); + int (*cam_to_XYZ)(struct _cam97s3 *s, double *out, double *in); + +/* Private: */ + /* Scene parameters */ + ViewingCondition Ev; /* Enumerated Viewing Condition */ + double Wxyz[3]; /* Reference/Adapted White XYZ (Y range 0.0 .. 1.0) */ + double Yb; /* Relative Luminance of Background to reference white (Y range 0.0 .. 1.0) */ + double La; /* Adapting/Surround Luminance cd/m^2 */ + double Yf; /* Flare as a fraction of the reference white (Y range 0.0 .. 1.0) */ + double Fxyz[3]; /* The Flare white coordinates (typically the Ambient color) */ + + /* Internal parameters */ + double C; /* Surround Impact */ + double Nc; /* Chromatic Induction */ + double F; /* Adaptation Degree */ + + /* Pre-computed values */ + double Fsc; /* Flare scale */ + double Fisc; /* Inverse flare scale */ + double Fsxyz[3]; /* Scaled Flare color coordinates */ + double rgbW[3]; /* Sharpened cone response white values */ + double D; /* Degree of chromatic adaption */ + double rgbcW[3]; /* Chromatically transformed white value */ + double rgbpW[3]; /* Hunt-Pointer-Estevez cone response space white */ + double n; /* Background induction factor */ + double nn; /* Precomuted function of n */ + double Fl; /* Lightness contrast factor ?? */ + double Nbb; /* Background brightness induction factors */ + double Ncb; /* Chromatic brightness induction factors */ + double z; /* Base exponential nonlinearity */ + double rgbaW[3]; /* Post-adapted cone response of white */ + double Aw; /* Achromatic response of white */ + + /* Flags */ + int hk; /* If NZ, use Helmholtz-Kohlraush effect */ + int trace; /* Trace values through computation */ +}; typedef struct _cam97s3 cam97s3; + + +/* Create a cam97s3 conversion class, with default viewing conditions */ +cam97s3 *new_cam97s3(void); + |