chromium/third_party/pdfium/third_party/lcms/src/cmssamp.c

//---------------------------------------------------------------------------------
//
//  Little Color Management System
//  Copyright (c) 1998-2023 Marti Maria Saguer
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the Software
// is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
// THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//---------------------------------------------------------------------------------
//

#include "lcms2_internal.h"


#define cmsmin(a, b) …
#define cmsmax(a, b) …

// This file contains routines for resampling and LUT optimization, black point detection
// and black preservation.

// Black point detection -------------------------------------------------------------------------


// PCS -> PCS round trip transform, always uses relative intent on the device -> pcs
static
cmsHTRANSFORM CreateRoundtripXForm(cmsHPROFILE hProfile, cmsUInt32Number nIntent)
{ … }

// Use darker colorants to obtain black point. This works in the relative colorimetric intent and
// assumes more ink results in darker colors. No ink limit is assumed.
static
cmsBool  BlackPointAsDarkerColorant(cmsHPROFILE    hInput,
                                    cmsUInt32Number Intent,
                                    cmsCIEXYZ* BlackPoint,
                                    cmsUInt32Number dwFlags)
{ … }

// Get a black point of output CMYK profile, discounting any ink-limiting embedded
// in the profile. For doing that, we use perceptual intent in input direction:
// Lab (0, 0, 0) -> [Perceptual] Profile -> CMYK -> [Rel. colorimetric] Profile -> Lab
static
cmsBool BlackPointUsingPerceptualBlack(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile)
{ … }

// This function shouldn't exist at all -- there is such quantity of broken
// profiles on black point tag, that we must somehow fix chromaticity to
// avoid huge tint when doing Black point compensation. This function does
// just that. There is a special flag for using black point tag, but turned
// off by default because it is bogus on most profiles. The detection algorithm
// involves to turn BP to neutral and to use only L component.
cmsBool CMSEXPORT cmsDetectBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
{ … }



// ---------------------------------------------------------------------------------------------------------

// Least Squares Fit of a Quadratic Curve to Data
// http://www.personal.psu.edu/jhm/f90/lectures/lsq2.html

static
cmsFloat64Number RootOfLeastSquaresFitQuadraticCurve(int n, cmsFloat64Number x[], cmsFloat64Number y[])
{ … }



// Calculates the black point of a destination profile.
// This algorithm comes from the Adobe paper disclosing its black point compensation method.
cmsBool CMSEXPORT cmsDetectDestinationBlackPoint(cmsCIEXYZ* BlackPoint, cmsHPROFILE hProfile, cmsUInt32Number Intent, cmsUInt32Number dwFlags)
{ … }