Drawing a line with gradient

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Hi,

I need to draw lines in my C#/WPF application, where the lines follow the mouse cursor movement.

I am able to trace the mouse cursor and show a blue-colored path.

How can I use gradient to create the line? Since I don't know the length of the line, I can't preset the individual colors of the gradient. Is there a way I can say "Change the line color from blue-yellow-red-blue gradually,and then repeat"?

Thanks!

Posted 10-Jun-14 1:57am

Member 3293815

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Richard MacCutchan · Answer 1 · 2014-06-10T03:09:00

Solution 1

See http://msdn.microsoft.com/en-us/library/aa970904(v=vs.110).aspx[^].

Posted 10-Jun-14 3:09am

Richard MacCutchan

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Member 3293815 12-Jun-14 6:01am

Hi Richard, thanks for the link!

I have gone through MSDN links, but none of them satisfied my requirements. To clarify my question further, I am implementing a timer. Every time timer goes out, I need to apply new color to the line.

Now, the color should be changed every second, so that the change in color is not abrupt. I am not able to choose color set, so that the change in color is gradual. Any suggestions, please?

Member 10272815 · Answer 2 · 2014-06-13T03:10:00

Something like this then?

System.Windows.Threading.DispatcherTimer timer = new System.Windows.Threading.DispatcherTimer();
Line gradientLine;
LinearGradientBrush gradBrush = new LinearGradientBrush();

        void Window_Loaded(object sender, RoutedEventArgs e)
        {
            gradBrush.GradientStops.Add(new GradientStop(Colors.Red, 0));
            gradBrush.GradientStops.Add(new GradientStop(Colors.Orange, 0.5));
            gradBrush.GradientStops.Add(new GradientStop(Colors.Yellow, 1));
            gradBrush.GradientStops.Add(new GradientStop(Colors.Green, 1.5));
            gradBrush.GradientStops.Add(new GradientStop(Colors.Blue, 2));
            gradBrush.GradientStops.Add(new GradientStop(Colors.Indigo, 2.5));
            gradBrush.GradientStops.Add(new GradientStop(Colors.Violet, 3));
            gradBrush.GradientStops.Add(new GradientStop(Colors.Purple, 3.5));
            gradientLine =  new Line() { X1 = 0, Y1 = 0, X2 = 100, Y2 = 100, StrokeThickness = 1, Stroke = gradBrush  };
            cnvCanvas.Children.Add(gradientLine);

            timer.Tick += timer_Tick;
            timer.Interval = new TimeSpan(0, 0, 0, 0, 1000/30);
            timer.Start();
        }

        void timer_Tick(object sender, EventArgs e)
        {
            for (int i = 0; i < gradBrush.GradientStops.Count; ++i)
            {
                gradBrush.GradientStops[i].Offset = gradBrush.GradientStops[i].Offset - 0.01;
                if (gradBrush.GradientStops[i].Offset < -1) gradBrush.GradientStops[i].Offset += 4;
            }

        }