//TODO: Let GL generate the texture using an FBO
void QOpenGL2GradientCache::generateGradientColorTable(const QGradient& gradient, uint *colorTable, int size, qreal opacity) const
{
int pos = 0;
QGradientStops s = gradient.stops();
QVector<uint> colors(s.size());
for (int i = 0; i < s.size(); ++i)
colors[i] = s[i].second.rgba(); // Qt LIES! It returns ARGB (on little-endian AND on big-endian)
bool colorInterpolation = (gradient.interpolationMode() == QGradient::ColorInterpolation);
uint alpha = qRound(opacity * 256);
uint current_color = ARGB_COMBINE_ALPHA(colors[0], alpha);
qreal incr = 1.0 / qreal(size);
qreal fpos = 1.5 * incr;
colorTable[pos++] = ARGB2RGBA(qPremultiply(current_color));
while (fpos <= s.first().first) {
colorTable[pos] = colorTable[pos - 1];
pos++;
fpos += incr;
}
if (colorInterpolation)
current_color = qPremultiply(current_color);
for (int i = 0; i < s.size() - 1; ++i) {
qreal delta = 1/(s[i+1].first - s[i].first);
uint next_color = ARGB_COMBINE_ALPHA(colors[i+1], alpha);
if (colorInterpolation)
next_color = qPremultiply(next_color);
while (fpos < s[i+1].first && pos < size) {
int dist = int(256 * ((fpos - s[i].first) * delta));
int idist = 256 - dist;
if (colorInterpolation)
colorTable[pos] = ARGB2RGBA(INTERPOLATE_PIXEL_256(current_color, idist, next_color, dist));
else
colorTable[pos] = ARGB2RGBA(qPremultiply(INTERPOLATE_PIXEL_256(current_color, idist, next_color, dist)));
++pos;
fpos += incr;
}
current_color = next_color;
}
Q_ASSERT(s.size() > 0);
uint last_color = ARGB2RGBA(qPremultiply(ARGB_COMBINE_ALPHA(colors[s.size() - 1], alpha)));
for (;pos < size; ++pos)
colorTable[pos] = last_color;
// Make sure the last color stop is represented at the end of the table
colorTable[size-1] = last_color;
}
QColor KarbonGradientHelper::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;
}