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-rw-r--r--libraries/rainbow/src/rainbow.cpp365
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+/* This was part of the KDE project - see KGuiAddons
+ * Copyright (C) 2007 Matthew Woehlke <mw_triad@users.sourceforge.net>
+ * Copyright (C) 2007 Olaf Schmidt <ojschmidt@kde.org>
+ * Copyright (C) 2007 Thomas Zander <zander@kde.org>
+ * Copyright (C) 2007 Zack Rusin <zack@kde.org>
+ * Copyright (C) 2015 Petr Mrazek <peterix@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB. If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "../include/rainbow.h"
+
+#include <QColor>
+#include <QImage>
+#include <QtNumeric> // qIsNaN
+
+#include <math.h>
+
+//BEGIN internal helper functions
+
+static inline qreal wrap(qreal a, qreal d = 1.0)
+{
+ qreal r = fmod(a, d);
+ return (r < 0.0 ? d + r : (r > 0.0 ? r : 0.0));
+}
+
+// normalize: like qBound(a, 0.0, 1.0) but without needing the args and with
+// "safer" behavior on NaN (isnan(a) -> return 0.0)
+static inline qreal normalize(qreal a)
+{
+ return (a < 1.0 ? (a > 0.0 ? a : 0.0) : 1.0);
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+// HCY color space
+
+#define HCY_REC 709 // use 709 for now
+#if HCY_REC == 601
+static const qreal yc[3] = {0.299, 0.587, 0.114};
+#elif HCY_REC == 709
+static const qreal yc[3] = {0.2126, 0.7152, 0.0722};
+#else // use Qt values
+static const qreal yc[3] = {0.34375, 0.5, 0.15625};
+#endif
+
+class KHCY
+{
+public:
+ explicit KHCY(const QColor &color)
+ {
+ qreal r = gamma(color.redF());
+ qreal g = gamma(color.greenF());
+ qreal b = gamma(color.blueF());
+ a = color.alphaF();
+
+ // luma component
+ y = lumag(r, g, b);
+
+ // hue component
+ qreal p = qMax(qMax(r, g), b);
+ qreal n = qMin(qMin(r, g), b);
+ qreal d = 6.0 * (p - n);
+ if (n == p)
+ {
+ h = 0.0;
+ }
+ else if (r == p)
+ {
+ h = ((g - b) / d);
+ }
+ else if (g == p)
+ {
+ h = ((b - r) / d) + (1.0 / 3.0);
+ }
+ else
+ {
+ h = ((r - g) / d) + (2.0 / 3.0);
+ }
+
+ // chroma component
+ if (r == g && g == b)
+ {
+ c = 0.0;
+ }
+ else
+ {
+ c = qMax((y - n) / y, (p - y) / (1 - y));
+ }
+ }
+ explicit KHCY(qreal h_, qreal c_, qreal y_, qreal a_ = 1.0)
+ {
+ h = h_;
+ c = c_;
+ y = y_;
+ a = a_;
+ }
+
+ QColor qColor() const
+ {
+ // start with sane component values
+ qreal _h = wrap(h);
+ qreal _c = normalize(c);
+ qreal _y = normalize(y);
+
+ // calculate some needed variables
+ qreal _hs = _h * 6.0, th, tm;
+ if (_hs < 1.0)
+ {
+ th = _hs;
+ tm = yc[0] + yc[1] * th;
+ }
+ else if (_hs < 2.0)
+ {
+ th = 2.0 - _hs;
+ tm = yc[1] + yc[0] * th;
+ }
+ else if (_hs < 3.0)
+ {
+ th = _hs - 2.0;
+ tm = yc[1] + yc[2] * th;
+ }
+ else if (_hs < 4.0)
+ {
+ th = 4.0 - _hs;
+ tm = yc[2] + yc[1] * th;
+ }
+ else if (_hs < 5.0)
+ {
+ th = _hs - 4.0;
+ tm = yc[2] + yc[0] * th;
+ }
+ else
+ {
+ th = 6.0 - _hs;
+ tm = yc[0] + yc[2] * th;
+ }
+
+ // calculate RGB channels in sorted order
+ qreal tn, to, tp;
+ if (tm >= _y)
+ {
+ tp = _y + _y * _c * (1.0 - tm) / tm;
+ to = _y + _y * _c * (th - tm) / tm;
+ tn = _y - (_y * _c);
+ }
+ else
+ {
+ tp = _y + (1.0 - _y) * _c;
+ to = _y + (1.0 - _y) * _c * (th - tm) / (1.0 - tm);
+ tn = _y - (1.0 - _y) * _c * tm / (1.0 - tm);
+ }
+
+ // return RGB channels in appropriate order
+ if (_hs < 1.0)
+ {
+ return QColor::fromRgbF(igamma(tp), igamma(to), igamma(tn), a);
+ }
+ else if (_hs < 2.0)
+ {
+ return QColor::fromRgbF(igamma(to), igamma(tp), igamma(tn), a);
+ }
+ else if (_hs < 3.0)
+ {
+ return QColor::fromRgbF(igamma(tn), igamma(tp), igamma(to), a);
+ }
+ else if (_hs < 4.0)
+ {
+ return QColor::fromRgbF(igamma(tn), igamma(to), igamma(tp), a);
+ }
+ else if (_hs < 5.0)
+ {
+ return QColor::fromRgbF(igamma(to), igamma(tn), igamma(tp), a);
+ }
+ else
+ {
+ return QColor::fromRgbF(igamma(tp), igamma(tn), igamma(to), a);
+ }
+ }
+
+ qreal h, c, y, a;
+ static qreal luma(const QColor &color)
+ {
+ return lumag(gamma(color.redF()), gamma(color.greenF()), gamma(color.blueF()));
+ }
+
+private:
+ static qreal gamma(qreal n)
+ {
+ return pow(normalize(n), 2.2);
+ }
+ static qreal igamma(qreal n)
+ {
+ return pow(normalize(n), 1.0 / 2.2);
+ }
+ static qreal lumag(qreal r, qreal g, qreal b)
+ {
+ return r * yc[0] + g * yc[1] + b * yc[2];
+ }
+};
+
+static inline qreal mixQreal(qreal a, qreal b, qreal bias)
+{
+ return a + (b - a) * bias;
+}
+//END internal helper functions
+
+qreal Rainbow::luma(const QColor &color)
+{
+ return KHCY::luma(color);
+}
+
+void Rainbow::getHcy(const QColor &color, qreal *h, qreal *c, qreal *y, qreal *a)
+{
+ if (!c || !h || !y)
+ {
+ return;
+ }
+ KHCY khcy(color);
+ *c = khcy.c;
+ *h = khcy.h;
+ *y = khcy.y;
+ if (a)
+ {
+ *a = khcy.a;
+ }
+}
+
+static qreal contrastRatioForLuma(qreal y1, qreal y2)
+{
+ if (y1 > y2)
+ {
+ return (y1 + 0.05) / (y2 + 0.05);
+ }
+ else
+ {
+ return (y2 + 0.05) / (y1 + 0.05);
+ }
+}
+
+qreal Rainbow::contrastRatio(const QColor &c1, const QColor &c2)
+{
+ return contrastRatioForLuma(luma(c1), luma(c2));
+}
+
+QColor Rainbow::lighten(const QColor &color, qreal ky, qreal kc)
+{
+ KHCY c(color);
+ c.y = 1.0 - normalize((1.0 - c.y) * (1.0 - ky));
+ c.c = 1.0 - normalize((1.0 - c.c) * kc);
+ return c.qColor();
+}
+
+QColor Rainbow::darken(const QColor &color, qreal ky, qreal kc)
+{
+ KHCY c(color);
+ c.y = normalize(c.y * (1.0 - ky));
+ c.c = normalize(c.c * kc);
+ return c.qColor();
+}
+
+QColor Rainbow::shade(const QColor &color, qreal ky, qreal kc)
+{
+ KHCY c(color);
+ c.y = normalize(c.y + ky);
+ c.c = normalize(c.c + kc);
+ return c.qColor();
+}
+
+static QColor tintHelper(const QColor &base, qreal baseLuma, const QColor &color, qreal amount)
+{
+ KHCY result(Rainbow::mix(base, color, pow(amount, 0.3)));
+ result.y = mixQreal(baseLuma, result.y, amount);
+
+ return result.qColor();
+}
+
+QColor Rainbow::tint(const QColor &base, const QColor &color, qreal amount)
+{
+ if (amount <= 0.0)
+ {
+ return base;
+ }
+ if (amount >= 1.0)
+ {
+ return color;
+ }
+ if (qIsNaN(amount))
+ {
+ return base;
+ }
+
+ qreal baseLuma = luma(base); // cache value because luma call is expensive
+ double ri = contrastRatioForLuma(baseLuma, luma(color));
+ double rg = 1.0 + ((ri + 1.0) * amount * amount * amount);
+ double u = 1.0, l = 0.0;
+ QColor result;
+ for (int i = 12; i; --i)
+ {
+ double a = 0.5 * (l + u);
+ result = tintHelper(base, baseLuma, color, a);
+ double ra = contrastRatioForLuma(baseLuma, luma(result));
+ if (ra > rg)
+ {
+ u = a;
+ }
+ else
+ {
+ l = a;
+ }
+ }
+ return result;
+}
+
+QColor Rainbow::mix(const QColor &c1, const QColor &c2, qreal bias)
+{
+ if (bias <= 0.0)
+ {
+ return c1;
+ }
+ if (bias >= 1.0)
+ {
+ return c2;
+ }
+ if (qIsNaN(bias))
+ {
+ return c1;
+ }
+
+ qreal r = mixQreal(c1.redF(), c2.redF(), bias);
+ qreal g = mixQreal(c1.greenF(), c2.greenF(), bias);
+ qreal b = mixQreal(c1.blueF(), c2.blueF(), bias);
+ qreal a = mixQreal(c1.alphaF(), c2.alphaF(), bias);
+
+ return QColor::fromRgbF(r, g, b, a);
+}
+
+QColor Rainbow::overlayColors(const QColor &base, const QColor &paint,
+ QPainter::CompositionMode comp)
+{
+ // This isn't the fastest way, but should be "fast enough".
+ // It's also the only safe way to use QPainter::CompositionMode
+ QImage img(1, 1, QImage::Format_ARGB32_Premultiplied);
+ QPainter p(&img);
+ QColor start = base;
+ start.setAlpha(255); // opaque
+ p.fillRect(0, 0, 1, 1, start);
+ p.setCompositionMode(comp);
+ p.fillRect(0, 0, 1, 1, paint);
+ p.end();
+ return img.pixel(0, 0);
+}