最近真是懒得一X，直接上代码。。。。。

最近搞Qt，需要利用QGis实现一些地理坐标显示还有插值图渲染功能。折腾了一大圈，终于实现了，记录一下，分享给需要的同学们。（￣︶￣）↗

安装QGis啥的就自己百度吧，很傻瓜，就是慢。。。

1. 引入相关头文件

#include <qgsapplication.h>
#include <qgsproviderregistry.h>
#include <qgsmapcanvas.h>
#include <qgsvectorlayer.h>
#include <qgsproject.h>
#include <qgsrasterlayer.h>
#include <QDialog>
#include <QFileDialog>
#include <QMessageBox>
#include "ogrsf_frmts.h"


// 功能函数的头文件
#include <qgssinglesymbolrenderer.h>
#include <qgsinterpolator.h>
#include <qgstininterpolator.h>
#include <qgsgridfilewriter.h>
#include "qgssinglebandpseudocolorrenderer.h"
#include <qgsrastershader.h>

2.修改主函数

注意此处用Release模式运行（不知道为啥，反正Debug就是错！！╮（╯＿╰）╭）

#include <qgsapplication.h>

int main(int argc, char *argv[])
{
    //QApplication a(argc, argv);  正常qt application的初始化
    QgsApplication a(argc, argv, true);
    QgsApplication::setPrefixPath("D:\\SoftWares\\QGIS\\install\\apps\\qgis\\plugins", true); 
    // 此处用自己的安装路径下面的库
    QgsApplication::initQgis();    //初始化QGIS应用
    APP w;
    w.show();
    return a.exec();
}

3. 添加图层向量

定义变量

QgsMapCanvas* mapCanvas; // 地图画布
//QList<QgsMapCanvasLayer> mapCanvasLayerSet; // 地图画布所用的图层集合
QList<QgsMapLayer*> layers;
QPushButton* train_button;

实现函数

void onClickedBtnAddVectorLayers()
{
    QString filename = QFileDialog::getOpenFileName(this, tr("open vector"), "", "*.shp");
    QStringList temp = filename.split(QDir::separator());
    QString basename = temp.at(temp.size() - 1);
    QgsVectorLayer* vecLayer = new QgsVectorLayer(filename, basename, "ogr");
    if (!vecLayer->isValid())
    {
        QMessageBox::critical(this, "error", "layer is invalid");
        return;
    }


    QgsProject::instance()->addMapLayer(vecLayer);
    //mapCanvas->setVisible(true);
    layers.append(vecLayer);
    mapCanvas->setExtent(vecLayer->extent());
    mapCanvas->setLayers(layers);
    mapCanvas->zoomToFullExtent();
    //mapCanvas->freeze(false);
    mapCanvas->refresh();
    
}

4. 添加栅格图层

本实现方法将栅格属性中的颜色表进行了自定义，实现了彩色渐变。可以自行修改！！！

void onClickedBtnAddRasterLayers()
{
    QString filename = QFileDialog::getOpenFileName(this, tr("open vector"), "", "*.tif");
    QStringList temp = filename.split(QDir::separator());
    QString basename = temp.at(temp.size() - 1);
    QgsRasterLayer* rasterLayer = new QgsRasterLayer(filename, basename, "gdal");
    if (!rasterLayer->isValid())
    {
        QMessageBox::critical(this, "error", "layer is invalid");
        return;
    }
    
    // 寻找栅格图层数据中的最大值和最小值
    double max_value = 0, min_value = 100000,op=0;
    max_value = rasterLayer->dataProvider()->bandStatistics(1).maximumValue;
    min_value = rasterLayer->dataProvider()->bandStatistics(1).minimumValue;
    op = (max_value - min_value) / 4;
    
    //ui.lineEdit->setText(QString::number(max_value));
    //ui.lineEdit_2->setText(QString::number(min_value));

    //获取当前默认Qgis工程
    QgsProject* project = QgsProject::instance();
    project->addMapLayer(rasterLayer);

    
    //构建一个栅格ColorRampItem列表，每个ColorRampItem表示栅格数据一个值对应一个颜色
    QList<QgsColorRampShader::ColorRampItem> crlist;
    //添加填充色
    crlist.append(QgsColorRampShader::ColorRampItem(min_value, QColor(143, 131, 86, 255), QString("Fill")));
    //添加云色
    crlist.append(QgsColorRampShader::ColorRampItem(min_value+op, QColor(171, 221, 164, 255), QString("Cloud")));
    //添加海洋水体颜色
    crlist.append(QgsColorRampShader::ColorRampItem(min_value+op*2, QColor(255, 255, 191, 255), QString("Sea")));
    //添加陆地颜色
    crlist.append(QgsColorRampShader::ColorRampItem(min_value + op * 3, QColor(253, 174, 97, 255), QString("Land")));
    //添加积雪颜色
    crlist.append(QgsColorRampShader::ColorRampItem(max_value, QColor(215, 25, 28, 255), QString("Snow")));
    //构建新的QgsColorRampShader 着色器
    QgsColorRampShader* crshader = new QgsColorRampShader(0, 100, nullptr, QgsColorRampShader::Type::Interpolated);
    //将颜色列表添加到着色器中
    crshader->setColorRampItemList(crlist);
    //构建栅格着色器，我也不知道为啥要包装这么多层
    QgsRasterShader* rasterShader = new QgsRasterShader();
    //设置渲染函数为刚刚新建的QgsColorRampShader 着色器
    rasterShader->setRasterShaderFunction(crshader);
    //构建一个伪彩色单波段渲染器，使用前面的栅格着色器作为输入，我也不明白为什么这么麻烦
    QgsSingleBandPseudoColorRenderer* pseudRender = new QgsSingleBandPseudoColorRenderer(
        rasterLayer->dataProvider(), 1, rasterShader);
    //栅格图层设置伪彩色单波段渲染器
    rasterLayer->setRenderer(pseudRender);

    
    layers.append(rasterLayer);
    mapCanvas->setExtent(rasterLayer->extent());
    mapCanvas->setLayers(layers);
    mapCanvas->zoomToFullExtent();
    mapCanvas->refresh();
}

5. 生成TIN插值图

void onClickedBtnGenerateTINMap()
{
    // 路径可修改为自己的 .shp 文件路径
    QgsVectorLayer* exp5Layer = new QgsVectorLayer("D:/newShp.shp", "shapefile", "ogr");

    const int index = 0;
    QgsInterpolator::LayerData ld5;

    ld5.source = exp5Layer;
    ld5.interpolationAttribute = index;
    ld5.sourceType = QgsInterpolator::SourceType::SourcePoints;
    ld5.valueSource = QgsInterpolator::ValueSource::ValueAttribute;

    QList<QgsInterpolator::LayerData> lds;
    lds.append(ld5);                                                                                                                                         
     
    QgsTinInterpolator* itp = new QgsTinInterpolator(lds);

    QgsWkbTypes::Type wkbType = exp5Layer->wkbType();
    QgsFields fields = exp5Layer->fields();

    // 范围选择图层范围，参数也可按自己需求修改（不明白参数的意思，可以先用QGis的Desktop软件试一试，功能对应）
    QgsRectangle rect = exp5Layer->extent();
    int ncol = (rect.xMaximum() - rect.xMinimum()) / 5;
    int nrow = (rect.yMaximum() - rect.yMinimum()) / 5;
    double current_y_value = rect.yMaximum() - 0.1 / 2.0;
    double current_x_value = rect.xMinimum() + 0.1 / 2.0;
    double interpolatedValue;

    QgsGridFileWriter* writer = new QgsGridFileWriter(itp, "D:/d.tif", rect, ncol, nrow);
    writer->writeFile();
    
}

效果图如下

[参考链接]
https://zhuanlan.zhihu.com/p/268609488
https://docs.qgis.org/3.16/en/docs/training_manual/processing/interpolation.html?highlight=interpolation
https://blog.csdn.net/deirjie/article/details/50413117
http://caiyi.tech/post.html?postKey=qgis_dev_1_env_setup
https://www.codenong.com/cs106838694/