Thanks for the reply Giuseppe ! You're right, the graph in the picture does not show exactly what I need to do: I do need a 3rd independent variable for the color of each point.
And if I understood you right, the solutions you mentioned won't fit my need, right ? On Thu, 21 Jun 2018 at 12:41, Giuseppe D'Angelo via Interest < [email protected]> wrote: > On 21/06/18 11:51, Massimiliano Maini wrote: > > I'd need to do something like this: https://imgur.com/MLAEuad > > > > I have a set of (x,y,z) data points and want to plot them on a usual 2d > > plot ( x and y values), but with the line color depending on the z > > values (colormap). > > > > How can this be achieved in Qt ? > > I'm not sure if I understood correctly; the graph in the picture isn't > using a third independent variable for the color of each point, rather > it's just using the y (in other words: the color of each point in the > line is just a function of its y coordinate.) > > Anyhow, short of using a complete graphing solution, you can easily > generate a vertical gradient using QLinearGradient (with the number of > stops you need), and the curve as a QPainterPath. Then you have a couple > of easy options: > > 1) set the curve as a clip path on a QPainter, and fill a rectangle with > the gradient (=> only the path will be filled), or > > 2) create a transparent QImage of suitable size, draw the path in some > solid color, and draw a rectangle filled with the gradient over the path > using some composition mode, e.g. SourceIn. Then draw the image on your > chart. > > HTH, > -- > Giuseppe D'Angelo | [email protected] | Senior Software Engineer > KDAB (France) S.A.S., a KDAB Group company > Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com > KDAB - The Qt, C++ and OpenGL Experts > > _______________________________________________ > Interest mailing list > [email protected] > http://lists.qt-project.org/mailman/listinfo/interest >
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