- Qt 6.6
- Qt Graphs
- Graph Gallery
- Qt Graphs | Commercial or GPLv3

# Graph Gallery

     // Copyright (C) 2023 The Qt Company Ltd.
     // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

     #include "topographicseries.h"

     // Value used to encode height data as RGB value on PNG file
     const float packingFactor = 11983.f;

     TopographicSeries::TopographicSeries()
     {
         setDrawMode(QSurface3DSeries::DrawSurface);
         setFlatShadingEnabled(true);
         setBaseColor(Qt::white);
     }

     TopographicSeries::~TopographicSeries() = default;

     void TopographicSeries::setTopographyFile(const QString file, float width, float height)
     {
         QImage heightMapImage(file);
         uchar *bits = heightMapImage.bits();
         int imageHeight = heightMapImage.height();
         int imageWidth = heightMapImage.width();
         int widthBits = imageWidth * 4;
         float stepX = width / float(imageWidth);
         float stepZ = height / float(imageHeight);

         auto *dataArray = new QSurfaceDataArray;
         dataArray->reserve(imageHeight);
         for (int i = 0; i < imageHeight; ++i) {
             int p = i * widthBits;
             float z = height - float(i) * stepZ;
             auto *newRow = new QSurfaceDataRow;
             newRow->reserve(imageWidth);
             for (int j = 0; j < imageWidth; ++j) {
                 uchar aa = bits[p + 0];
                 uchar rr = bits[p + 1];
                 uchar gg = bits[p + 2];
                 uint color = uint((gg << 16) + (rr << 8) + aa);
                 float y = float(color) / packingFactor;
                 newRow->append(QSurfaceDataItem({float(j) * stepX, y, z}));
                 p += 4;
             }
             dataArray->append(newRow);
         }

         dataProxy()->resetArray(dataArray);

         m_sampleCountX = float(imageWidth);
         m_sampleCountZ = float(imageHeight);
     }