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);

     QSurfaceDataArray dataArray;
     dataArray.reserve(imageHeight);
     for (int i = 0; i < imageHeight; ++i) {
         int p = i * widthBits;
         float z = height - float(i) * stepZ;
         QSurfaceDataRow newRow;
         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);
 }