The PaletteProvider feature allows you to change color of a scatter point, line segment, mountain segment, OHLC/Candlestick bar or column based on the data-value, or other data in your data-point.

This feature was notoriously slow when used in conjunction with XyScatterRenderableSeries and users demanded more performance.

As a result, we developed the ExtremeScatterRenderableSeries – a DirectX only scatter series type optimised for Big-Data and color changes via a PaletteProvider-like API.

// FastPalettedScatterCharts.xaml

<UserControl x:Class="SciChart.Examples.Examples.PerformanceDemos2D.ScatterPerf.FastPalettedScatterCharts"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:s="http://schemas.abtsoftware.co.uk/scichart"
             xmlns:ext="http://schemas.abtsoftware.co.uk/scichart/exampleExternals"
             mc:Ignorable="d" 
             d:DesignHeight="500"
             d:DesignWidth="800">
    
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>

        <!-- The SciChartInteractionToolbar adds zoom, pan, zoom extents and rotate functionality -->
        <!-- to the chart and is included for example purposes. -->
        <!-- If you wish to know how to zoom and pan a chart then do a search for Zoom Pan in the Examples suite! -->
        <ext:SciChartInteractionToolbar TargetSurface="{Binding Source={x:Reference Name=sciChart}}"/>

        <s:SciChartSurface x:Name="sciChart" Grid.Column="1">
            <s:SciChartSurface.XAxis>
                <s:NumericAxis/>
            </s:SciChartSurface.XAxis>

            <s:SciChartSurface.YAxis>
                <s:NumericAxis/>
            </s:SciChartSurface.YAxis>

            <s:SciChartSurface.Annotations>
                <s:TextAnnotation x:Name="warningText" 
                                  Text="The ExtremeScatterRenderableSeries is only available when DirectX hardware acceleration is available." 
                                  X1="0.5" Y1="0.5"
                                  CoordinateMode="Relative"
                                  HorizontalAnchorPoint="Center"
                                  Foreground="#FF6600"/>
            </s:SciChartSurface.Annotations>
        </s:SciChartSurface>
    </Grid>
</UserControl>

// FastPalettedScatterCharts.xaml.cs

using System;
using System.Collections.Generic;
using System.Windows.Controls;
using System.Windows.Media;
using SciChart.Charting;
using SciChart.Charting.Model.DataSeries;
using SciChart.Charting.Visuals.PointMarkers;
using SciChart.Charting.Visuals.RenderableSeries;
using SciChart.Data.Model;

namespace SciChart.Examples.Examples.PerformanceDemos2D.ScatterPerf
{
    /// <summary>
    /// Interaction logic for FastPalettedScatterCharts.xaml
    /// </summary>
    public partial class FastPalettedScatterCharts : UserControl
    {
        public FastPalettedScatterCharts()
        {
            InitializeComponent();

            if (VisualXcceleratorEngine.SupportsHardwareAcceleration)
            {
                warningText.IsHidden = true;
                SetupScatterSeries();
            }
            else
            {
                warningText.IsHidden = false;
            }
        }

        private void SetupScatterSeries()
        {
            var dataSeries = new XyDataSeries<double, double>() { AcceptsUnsortedData = true };

            var random = new Random(0);
            var dataPointColors = new List<Color>();

            for (int i = 0; i < 100000; i++)
            {
                dataSeries.Append(random.NextDouble(), random.NextDouble());
                dataPointColors.Add(GetRandomColor(random));
            }

            var scatterSeries = new ExtremeScatterRenderableSeries()
            {
                PointMarker = new EllipsePointMarker() {Width = 5, Height = 5}
            };
            sciChart.RenderableSeries.Add(scatterSeries);
            scatterSeries.DataSeries = dataSeries;
            scatterSeries.PaletteProvider = new TestPaletteProvider(dataPointColors);
        }

        private static Color GetRandomColor(Random random)
        {
            return Color.FromArgb(0xFF, (byte)random.Next(255), (byte)random.Next(255), (byte)random.Next(255));
        }
    }

    public class TestPaletteProvider : IExtremePointMarkerPaletteProvider
    {
        private readonly List<Color> _dataPointColors;
        private readonly Values<Color> _colors = new Values<Color>();

        public TestPaletteProvider(List<Color> dataPointColors)
        {
            _dataPointColors = dataPointColors;
        }

        public Values<Color> Colors { get { return _colors; } }

        public void OnBeginSeriesDraw(IRenderableSeries rSeries)
        {
            var indexes = rSeries.CurrentRenderPassData.PointSeries.Indexes;

            var count = indexes.Count;
            _colors.Count = count;

            // copy required colors from list using data point indices
            for (int i = 0; i < count; i++)
            {
                var dataPointIndex = indexes[i];
                _colors[i] = _dataPointColors[dataPointIndex];
            }
        }
    }
}

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