QtCharts is it posible to have gradient lines?

linuxTown

Hi,

Could I achieve this kind of spline chart with QTCharts, where color changes according to y chart value?

example:
alt text

mrjj

Hi
Maybe you can use
https://doc.qt.io/qt-5.10/qtcharts-customchart-example.html
and draw the gradient as background and let graph be transparent on the actual
plot values.

alt text

linuxTown

Ok, I will try to do that, thanks

linuxTown

How to make line be transparent like in that picture? Because if I set it like this:

QPen green(QColor(0, 0, 0, 0x00));
green.setWidth(2);
m_series->setPen(green);

line just becomes invisible. If I set chart background like this:
QBrush brush (QImage(":image/image.png"));
chart->setPlotAreaBackgroundBrush(brush);
chart->setPlotAreaBackgroundVisible(true);
whole chart area then has that image and line is still invisible. if I setPlotAreaBackgroundVisible(false) background disappears, but line is still invisible. How to have, that only chart line shows that background?

linuxTown

So it means it's impossible to achieve this with QT charts?

VRonin

Starting from the aforementioned example, replace

// Customize series
QPen pen(QRgb(0xfdb157));
    pen.setWidth(5);
    series->setPen(pen);

with

QLinearGradient lineGradient;
    lineGradient.setStart(QPointF(0, 1));
    lineGradient.setFinalStop(QPointF(1, 0));
    lineGradient.setColorAt(0.0, Qt::blue);
    lineGradient.setColorAt(1.0, Qt::red);
    lineGradient.setCoordinateMode(QGradient::StretchToDeviceMode);
    series->setPen(QPen(QBrush(lineGradient),5));

linuxTown

Hi VRonin,

Thank you a lot, that works perfectly!!!