A ProEssentials v10 WPF .NET 8 demonstration of a full-featured heatmap, spectrogram, and 2D contour chart using PesgoWpf — the ProEssentials scientific graph object for continuous numeric X and Y axes.

➡️ gigasoft.com/examples/139

183 subsets × 512 points = 93,696 Z values rendered as a smooth interpolated color heatmap with a logarithmic frequency Y axis — the classic spectrogram layout used in signal analysis, acoustics, RF engineering, and vibration analysis.

This example uses PesgoWpf (Scientific Graph), not PegoWpf (Graph).

When both X and Y carry continuous numeric values — as in frequency vs time — PesgoWpf is the correct choice.

Pesgo1.PePlot.Allow.ContourColors        = true;
Pesgo1.PePlot.Allow.ContourColorsShadows = true;
Pesgo1.PeColor.ContourColorBlends        = 10;  // set BEFORE ContourColorSet
Pesgo1.PeColor.ContourColorSet           = ContourColorSet.BlueCyanGreenYellowBrownWhite;
Pesgo1.PePlot.Method                     = SGraphPlottingMethod.ContourColors;

ContourColors fills the regions between contour lines with interpolated color — the standard heatmap/spectrogram technique. Each Z value maps to a color in the BlueCyanGreenYellowBrownWhite scale:

• Blue — low amplitude
• Cyan → Green → Yellow — mid range
• Brown → White — high amplitude

ContourColorBlends must always be set before ContourColorSet.

Pesgo1.PeGrid.Configure.YAxisScaleControl = ScaleControl.Log;

Logarithmic Y axis gives equal visual space per octave — standard for frequency data where the perceptually important differences are proportional, not absolute.

Pesgo1.PeData.DuplicateDataX = DuplicateData.PointIncrement;
Pesgo1.PeData.DuplicateDataY = DuplicateData.SubsetIncrement;

Only one row of X values (512) and one column of Y values (183) are stored. The chart duplicates them internally — avoids allocating and passing 93,696 X and 93,696 Y values separately.

Pesgo1.PeConfigure.Composite2D3D = Composite2D3D.Foreground;
Pesgo1.PeConfigure.RenderEngine  = RenderEngine.Direct3D;
Pesgo1.PeData.ComputeShader      = true;

Composite2D3D.Foreground renders the contour fill using the Direct3D GPU pipeline, then composites the 2D axis, grid, and labels on top — combining GPU performance with crisp 2D text rendering.

ComputeShader delegates contour color interpolation to the GPU — significant speedup for large heatmap datasets.

Pesgo1.PeUserInterface.Cursor.PromptTracking = true;
Pesgo1.PeUserInterface.Cursor.PromptStyle    = CursorPromptStyle.XYZValues;
Pesgo1.PeUserInterface.Cursor.PromptLocation = CursorPromptLocation.Text;

Hover over the heatmap to read the exact X frequency, Y frequency, and Z amplitude at the cursor position — displayed as text inside the chart.

Pesgo1.PeData.X[0, 511]   = 0; // pre-allocate X
Pesgo1.PeData.Y[0, 182]   = 0; // pre-allocate Y
Pesgo1.PeData.Z[182, 511] = 0; // pre-allocate Z

Setting the last element of each array before the load loop guarantees the internal arrays are fully sized upfront — no incremental reallocations during data load.

Heatmap.txt — 93,696 lines, tab-delimited X/Y/Z per line. 183 rows (subsets) × 512 columns (points).

• X — frequency offset per column
• Y — frequency per row (scaled for log axis)
• Z — signal amplitude (the heatmap color value)

Copied to the output directory automatically on build.

• Visual Studio 2022
• .NET 8 SDK
• Internet connection for NuGet restore

1. Clone this repository
2. Open HeatmapSpectrogram.sln in Visual Studio 2022
3. Build → Rebuild Solution (NuGet restore is automatic)
4. Press F5

References ProEssentials.Chart.Net80.x64.Wpf. Package restore is automatic on build.

• WPF Quickstart — Simple Scientific Graph
• Financial OHLC — Trading Signals
• 3D Realtime Surface — ComputeShader
• All Examples — GigasoftInc on GitHub
• Full Evaluation Download
• gigasoft.com

Example code is MIT licensed. ProEssentials requires a commercial license for continued use.