Java example source code file (cmssamp.c)
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// This file is available under and governed by the GNU General Public
// License version 2 only, as published by the Free Software Foundation.
// However, the following notice accompanied the original version of this
// file:
//
//---------------------------------------------------------------------------------
//
// Little Color Management System
// Copyright (c) 1998-2010 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"
// 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)
{
cmsHPROFILE hLab = cmsCreateLab4Profile(NULL);
cmsHTRANSFORM xform;
cmsBool BPC[4] = { FALSE, FALSE, FALSE, FALSE };
cmsFloat64Number States[4] = { 1.0, 1.0, 1.0, 1.0 };
cmsHPROFILE hProfiles[4];
cmsUInt32Number Intents[4];
cmsContext ContextID = cmsGetProfileContextID(hProfile);
hProfiles[0] = hLab; hProfiles[1] = hProfile; hProfiles[2] = hProfile; hProfiles[3] = hLab;
Intents[0] = INTENT_RELATIVE_COLORIMETRIC; Intents[1] = nIntent; Intents[2] = INTENT_RELATIVE_COLORIMETRIC; Intents[3] = INTENT_RELATIVE_COLORIMETRIC;
xform = cmsCreateExtendedTransform(ContextID, 4, hProfiles, BPC, Intents,
States, NULL, 0, TYPE_Lab_DBL, TYPE_Lab_DBL, cmsFLAGS_NOCACHE|cmsFLAGS_NOOPTIMIZE);
cmsCloseProfile(hLab);
return xform;
}
// 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)
{
cmsUInt16Number *Black;
cmsHTRANSFORM xform;
cmsColorSpaceSignature Space;
cmsUInt32Number nChannels;
cmsUInt32Number dwFormat;
cmsHPROFILE hLab;
cmsCIELab Lab;
cmsCIEXYZ BlackXYZ;
cmsContext ContextID = cmsGetProfileContextID(hInput);
// If the profile does not support input direction, assume Black point 0
if (!cmsIsIntentSupported(hInput, Intent, LCMS_USED_AS_INPUT)) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
// Create a formatter which has n channels and floating point
dwFormat = cmsFormatterForColorspaceOfProfile(hInput, 2, FALSE);
// Try to get black by using black colorant
Space = cmsGetColorSpace(hInput);
// This function returns darker colorant in 16 bits for several spaces
if (!_cmsEndPointsBySpace(Space, NULL, &Black, &nChannels)) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
if (nChannels != T_CHANNELS(dwFormat)) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
// Lab will be used as the output space, but lab2 will avoid recursion
hLab = cmsCreateLab2ProfileTHR(ContextID, NULL);
if (hLab == NULL) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
// Create the transform
xform = cmsCreateTransformTHR(ContextID, hInput, dwFormat,
hLab, TYPE_Lab_DBL, Intent, cmsFLAGS_NOOPTIMIZE|cmsFLAGS_NOCACHE);
cmsCloseProfile(hLab);
if (xform == NULL) {
// Something went wrong. Get rid of open resources and return zero as black
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
// Convert black to Lab
cmsDoTransform(xform, Black, &Lab, 1);
// Force it to be neutral, clip to max. L* of 50
Lab.a = Lab.b = 0;
if (Lab.L > 50) Lab.L = 50;
// Free the resources
cmsDeleteTransform(xform);
// Convert from Lab (which is now clipped) to XYZ.
cmsLab2XYZ(NULL, &BlackXYZ, &Lab);
if (BlackPoint != NULL)
*BlackPoint = BlackXYZ;
return TRUE;
cmsUNUSED_PARAMETER(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)
{
cmsHTRANSFORM hRoundTrip;
cmsCIELab LabIn, LabOut;
cmsCIEXYZ BlackXYZ;
// Is the intent supported by the profile?
if (!cmsIsIntentSupported(hProfile, INTENT_PERCEPTUAL, LCMS_USED_AS_INPUT)) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return TRUE;
}
hRoundTrip = CreateRoundtripXForm(hProfile, INTENT_PERCEPTUAL);
if (hRoundTrip == NULL) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
LabIn.L = LabIn.a = LabIn.b = 0;
cmsDoTransform(hRoundTrip, &LabIn, &LabOut, 1);
// Clip Lab to reasonable limits
if (LabOut.L > 50) LabOut.L = 50;
LabOut.a = LabOut.b = 0;
cmsDeleteTransform(hRoundTrip);
// Convert it to XYZ
cmsLab2XYZ(NULL, &BlackXYZ, &LabOut);
if (BlackPoint != NULL)
*BlackPoint = BlackXYZ;
return TRUE;
}
// 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)
{
// Zero for black point
if (cmsGetDeviceClass(hProfile) == cmsSigLinkClass) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
// v4 + perceptual & saturation intents does have its own black point, and it is
// well specified enough to use it. Black point tag is deprecated in V4.
if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&
(Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
// Matrix shaper share MRC & perceptual intents
if (cmsIsMatrixShaper(hProfile))
return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
// Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
return TRUE;
}
#ifdef CMS_USE_PROFILE_BLACK_POINT_TAG
// v2, v4 rel/abs colorimetric
if (cmsIsTag(hProfile, cmsSigMediaBlackPointTag) &&
Intent == INTENT_RELATIVE_COLORIMETRIC) {
cmsCIEXYZ *BlackPtr, BlackXYZ, UntrustedBlackPoint, TrustedBlackPoint, MediaWhite;
cmsCIELab Lab;
// If black point is specified, then use it,
BlackPtr = cmsReadTag(hProfile, cmsSigMediaBlackPointTag);
if (BlackPtr != NULL) {
BlackXYZ = *BlackPtr;
_cmsReadMediaWhitePoint(&MediaWhite, hProfile);
// Black point is absolute XYZ, so adapt to D50 to get PCS value
cmsAdaptToIlluminant(&UntrustedBlackPoint, &MediaWhite, cmsD50_XYZ(), &BlackXYZ);
// Force a=b=0 to get rid of any chroma
cmsXYZ2Lab(NULL, &Lab, &UntrustedBlackPoint);
Lab.a = Lab.b = 0;
if (Lab.L > 50) Lab.L = 50; // Clip to L* <= 50
cmsLab2XYZ(NULL, &TrustedBlackPoint, &Lab);
if (BlackPoint != NULL)
*BlackPoint = TrustedBlackPoint;
return TRUE;
}
}
#endif
// That is about v2 profiles.
// If output profile, discount ink-limiting and that's all
if (Intent == INTENT_RELATIVE_COLORIMETRIC &&
(cmsGetDeviceClass(hProfile) == cmsSigOutputClass) &&
(cmsGetColorSpace(hProfile) == cmsSigCmykData))
return BlackPointUsingPerceptualBlack(BlackPoint, hProfile);
// Nope, compute BP using current intent.
return BlackPointAsDarkerColorant(hProfile, Intent, BlackPoint, 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[])
{
double sum_x = 0, sum_x2 = 0, sum_x3 = 0, sum_x4 = 0;
double sum_y = 0, sum_yx = 0, sum_yx2 = 0;
double disc;
int i;
cmsMAT3 m;
cmsVEC3 v, res;
if (n < 4) return 0;
for (i=0; i < n; i++) {
double xn = x[i];
double yn = y[i];
sum_x += xn;
sum_x2 += xn*xn;
sum_x3 += xn*xn*xn;
sum_x4 += xn*xn*xn*xn;
sum_y += yn;
sum_yx += yn*xn;
sum_yx2 += yn*xn*xn;
}
_cmsVEC3init(&m.v[0], n, sum_x, sum_x2);
_cmsVEC3init(&m.v[1], sum_x, sum_x2, sum_x3);
_cmsVEC3init(&m.v[2], sum_x2, sum_x3, sum_x4);
_cmsVEC3init(&v, sum_y, sum_yx, sum_yx2);
if (!_cmsMAT3solve(&res, &m, &v)) return 0;
// y = t x2 + u x + c
// x = ( - u + Sqrt( u^2 - 4 t c ) ) / ( 2 t )
disc = res.n[1]*res.n[1] - 4.0 * res.n[0] * res.n[2];
if (disc < 0) return -1;
return ( -1.0 * res.n[1] + sqrt( disc )) / (2.0 * res.n[0]);
}
static
cmsBool IsMonotonic(int n, const cmsFloat64Number Table[])
{
int i;
cmsFloat64Number last;
last = Table[n-1];
for (i = n-2; i >= 0; --i) {
if (Table[i] > last)
return FALSE;
else
last = Table[i];
}
return TRUE;
}
// 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)
{
cmsColorSpaceSignature ColorSpace;
cmsHTRANSFORM hRoundTrip = NULL;
cmsCIELab InitialLab, destLab, Lab;
cmsFloat64Number MinL, MaxL;
cmsBool NearlyStraightMidRange = FALSE;
cmsFloat64Number L;
cmsFloat64Number x[101], y[101];
cmsFloat64Number lo, hi, NonMonoMin;
int n, l, i, NonMonoIndx;
// Make sure intent is adequate
if (Intent != INTENT_PERCEPTUAL &&
Intent != INTENT_RELATIVE_COLORIMETRIC &&
Intent != INTENT_SATURATION) {
BlackPoint -> X = BlackPoint ->Y = BlackPoint -> Z = 0.0;
return FALSE;
}
// v4 + perceptual & saturation intents does have its own black point, and it is
// well specified enough to use it. Black point tag is deprecated in V4.
if ((cmsGetEncodedICCversion(hProfile) >= 0x4000000) &&
(Intent == INTENT_PERCEPTUAL || Intent == INTENT_SATURATION)) {
// Matrix shaper share MRC & perceptual intents
if (cmsIsMatrixShaper(hProfile))
return BlackPointAsDarkerColorant(hProfile, INTENT_RELATIVE_COLORIMETRIC, BlackPoint, 0);
// Get Perceptual black out of v4 profiles. That is fixed for perceptual & saturation intents
BlackPoint -> X = cmsPERCEPTUAL_BLACK_X;
BlackPoint -> Y = cmsPERCEPTUAL_BLACK_Y;
BlackPoint -> Z = cmsPERCEPTUAL_BLACK_Z;
return TRUE;
}
// Check if the profile is lut based and gray, rgb or cmyk (7.2 in Adobe's document)
ColorSpace = cmsGetColorSpace(hProfile);
if (!cmsIsCLUT(hProfile, Intent, LCMS_USED_AS_OUTPUT ) ||
(ColorSpace != cmsSigGrayData &&
ColorSpace != cmsSigRgbData &&
ColorSpace != cmsSigCmykData)) {
// In this case, handle as input case
return cmsDetectBlackPoint(BlackPoint, hProfile, Intent, dwFlags);
}
// It is one of the valid cases!, presto chargo hocus pocus, go for the Adobe magic
// Step 1
// ======
// Set a first guess, that should work on good profiles.
if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
cmsCIEXYZ IniXYZ;
// calculate initial Lab as source black point
if (!cmsDetectBlackPoint(&IniXYZ, hProfile, Intent, dwFlags)) {
return FALSE;
}
// convert the XYZ to lab
cmsXYZ2Lab(NULL, &InitialLab, &IniXYZ);
} else {
// set the initial Lab to zero, that should be the black point for perceptual and saturation
InitialLab.L = 0;
InitialLab.a = 0;
InitialLab.b = 0;
}
// Step 2
// ======
// Create a roundtrip. Define a Transform BT for all x in L*a*b*
hRoundTrip = CreateRoundtripXForm(hProfile, Intent);
if (hRoundTrip == NULL) return FALSE;
// Calculate Min L*
Lab = InitialLab;
Lab.L = 0;
cmsDoTransform(hRoundTrip, &Lab, &destLab, 1);
MinL = destLab.L;
// Calculate Max L*
Lab = InitialLab;
Lab.L = 100;
cmsDoTransform(hRoundTrip, &Lab, &destLab, 1);
MaxL = destLab.L;
// Step 3
// ======
// check if quadratic estimation needs to be done.
if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
// Conceptually, this code tests how close the source l and converted L are to one another in the mid-range
// of the values. If the converted ramp of L values is close enough to a straight line y=x, then InitialLab
// is good enough to be the DestinationBlackPoint,
NearlyStraightMidRange = TRUE;
for (l=0; l <= 100; l++) {
Lab.L = l;
Lab.a = InitialLab.a;
Lab.b = InitialLab.b;
cmsDoTransform(hRoundTrip, &Lab, &destLab, 1);
L = destLab.L;
// Check the mid range in 20% after MinL
if (L > (MinL + 0.2 * (MaxL - MinL))) {
// Is close enough?
if (fabs(L - l) > 4.0) {
// Too far away, profile is buggy!
NearlyStraightMidRange = FALSE;
break;
}
}
}
}
else {
// Check is always performed for perceptual and saturation intents
NearlyStraightMidRange = FALSE;
}
// If no furter checking is needed, we are done
if (NearlyStraightMidRange) {
cmsLab2XYZ(NULL, BlackPoint, &InitialLab);
cmsDeleteTransform(hRoundTrip);
return TRUE;
}
// The round-trip curve normally looks like a nearly constant section at the black point,
// with a corner and a nearly straight line to the white point.
// STEP 4
// =======
// find the black point using the least squares error quadratic curve fitting
if (Intent == INTENT_RELATIVE_COLORIMETRIC) {
lo = 0.1;
hi = 0.5;
}
else {
// Perceptual and saturation
lo = 0.03;
hi = 0.25;
}
// Capture points for the fitting.
n = 0;
for (l=0; l <= 100; l++) {
cmsFloat64Number ff;
Lab.L = (cmsFloat64Number) l;
Lab.a = InitialLab.a;
Lab.b = InitialLab.b;
cmsDoTransform(hRoundTrip, &Lab, &destLab, 1);
ff = (destLab.L - MinL)/(MaxL - MinL);
if (ff >= lo && ff < hi) {
x[n] = Lab.L;
y[n] = ff;
n++;
}
}
// This part is not on the Adobe paper, but I found is necessary for getting any result.
if (IsMonotonic(n, y)) {
// Monotonic means lower point is stil valid
cmsLab2XYZ(NULL, BlackPoint, &InitialLab);
cmsDeleteTransform(hRoundTrip);
return TRUE;
}
// No suitable points, regret and use safer algorithm
if (n == 0) {
cmsDeleteTransform(hRoundTrip);
return cmsDetectBlackPoint(BlackPoint, hProfile, Intent, dwFlags);
}
NonMonoMin = 100;
NonMonoIndx = 0;
for (i=0; i < n; i++) {
if (y[i] < NonMonoMin) {
NonMonoIndx = i;
NonMonoMin = y[i];
}
}
Lab.L = x[NonMonoIndx];
// fit and get the vertex of quadratic curve
Lab.L = RootOfLeastSquaresFitQuadraticCurve(n, x, y);
if (Lab.L < 0.0 || Lab.L > 50.0) { // clip to zero L* if the vertex is negative
Lab.L = 0;
}
Lab.a = InitialLab.a;
Lab.b = InitialLab.b;
cmsLab2XYZ(NULL, BlackPoint, &Lab);
cmsDeleteTransform(hRoundTrip);
return TRUE;
}
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