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 /* This file is part of the KDE project
  * Copyright (C) 2008 Jan Hambrecht <jaham@gmx.net>
  *
  * 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 "KoGradientHelper.h"
 
 #include <QGradient>
 #include <math.h>
 
 QGradient* KoGradientHelper::defaultGradient(QGradient::Type type, QGradient::Spread spread, const QGradientStops &stops)
 {
     QGradient *gradient = 0;
     switch (type) {
     case QGradient::LinearGradient:
         gradient = new QLinearGradient(QPointF(0.0, 0.5), QPointF(1, 0.5));
         break;
     case QGradient::RadialGradient:
         gradient = new QRadialGradient(QPointF(0.5, 0.5), sqrt(0.5));
         break;
     case QGradient::ConicalGradient:
         gradient = new QConicalGradient(QPointF(0.5, 0.5), 0.0);
         break;
     default:
         return 0;
     }
     gradient->setCoordinateMode(QGradient::ObjectBoundingMode);
     gradient->setSpread(spread);
     gradient->setStops(stops);
 
     return gradient;
 }
 
 QGradient* KoGradientHelper::convertGradient(const QGradient * gradient, QGradient::Type newType)
 {
     QPointF start, stop;
     // try to preserve gradient positions
     switch (gradient->type()) {
     case QGradient::LinearGradient: {
         const QLinearGradient *g = static_cast<const QLinearGradient*>(gradient);
         start = g->start();
         stop = g->finalStop();
         break;
     }
     case QGradient::RadialGradient: {
         const QRadialGradient *g = static_cast<const QRadialGradient*>(gradient);
         start = g->center();
         stop = QPointF(g->radius(), 0.0);
         break;
     }
     case QGradient::ConicalGradient: {
         const QConicalGradient *g = static_cast<const QConicalGradient*>(gradient);
         start = g->center();
         qreal radAngle = g->angle() * M_PI / 180.0;
         stop = QPointF(0.5 * cos(radAngle), 0.5 * sin(radAngle));
         break;
     }
     default:
         start = QPointF(0.0, 0.0);
         stop = QPointF(0.5, 0.5);
     }
 
     QGradient *newGradient = 0;
     switch (newType) {
     case QGradient::LinearGradient:
         newGradient = new QLinearGradient(start, stop);
         break;
     case QGradient::RadialGradient: {
         QPointF diff(stop - start);
         qreal radius = sqrt(diff.x()*diff.x() + diff.y()*diff.y());
         newGradient = new QRadialGradient(start, radius, start);
         break;
     }
     case QGradient::ConicalGradient: {
         QPointF diff(stop - start);
         qreal angle = atan2(diff.y(), diff.x());
         if (angle < 0.0)
             angle += 2 * M_PI;
         newGradient = new QConicalGradient(start, angle * 180/M_PI);
         break;
     }
     default:
         return 0;
     }
     newGradient->setCoordinateMode(QGradient::ObjectBoundingMode);
     newGradient->setSpread(gradient->spread());
     newGradient->setStops(gradient->stops());
 
     return newGradient;
 }
 
 QColor KoGradientHelper::colorAt(qreal position, const QGradientStops &stops)
 {
     if (! stops.count())
         return QColor();
 
     if (stops.count() == 1)
         return stops.first().second;
 
     QGradientStop prevStop(-1.0, QColor());
     QGradientStop nextStop(2.0, QColor());
     // find framing gradient stops
     foreach(const QGradientStop & stop, stops) {
         if (stop.first > prevStop.first && stop.first < position)
             prevStop = stop;
         if (stop.first < nextStop.first && stop.first > position)
             nextStop = stop;
     }
 
     QColor theColor;
 
     if (prevStop.first < 0.0) {
         // new stop is before the first stop
         theColor = nextStop.second;
     } else if (nextStop.first > 1.0) {
         // new stop is after the last stop
         theColor = prevStop.second;
     } else {
         // linear interpolate colors between framing stops
         QColor prevColor = prevStop.second, nextColor = nextStop.second;
         qreal colorScale = (position - prevStop.first) / (nextStop.first - prevStop.first);
         theColor.setRedF(prevColor.redF() + colorScale *(nextColor.redF() - prevColor.redF()));
         theColor.setGreenF(prevColor.greenF() + colorScale *(nextColor.greenF() - prevColor.greenF()));
         theColor.setBlueF(prevColor.blueF() + colorScale *(nextColor.blueF() - prevColor.blueF()));
         theColor.setAlphaF(prevColor.alphaF() + colorScale *(nextColor.alphaF() - prevColor.alphaF()));
     }
     return theColor;
 }