c++ - GDAL C++ RasterIO 按 block

Question

我是 gdal 和 c++ 的新手，我正在尝试创建一个按 block 读取栅格的函数(使用 RasterIO 而不是 ReadBlock)对值执行某些操作并将结果写入新的栅格文件

我收到一个错误:

Unhandled exception at 0x00007FFDFB517BC4 (gdal201.dll) in Test.exe: 0xC0000005: Access violation writing location 0x00000230E2593000 at line rasterBand->RasterIO(GDALRWFlag::GF_Read, j * readCols, i * readRows, readCols, readRows, rasterBlock, readCols, readRows, GDALDataType::GDT_CFloat32, 0, 0)

我有一个非常相似的函数可以正常工作，但它会逐行读取像素值

感谢任何帮助

函数如下

谢谢

#include <iostream>
#include "gdal_priv.h"
using namespace std;

void SlopeBlock()
{
int readRows = 2048;
int readCols = 2048;
int nBlockXSize;
int nBlockYSize;
int rowOff = 0;
int colOff = 0;
int nRows = 0;
int nCols = 0;
double noData = -9999;

GDALAllRegister();

GDALDataset* dem = (GDALDataset*)GDALOpen("path/EUD_CP-DEMS_4500025000-AA.tif", GA_ReadOnly);

GDALDriver *gTIF = GetGDALDriverManager()->GetDriverByName(dem->GetDriverName());

double geoTransform[6];
dem->GetGeoTransform(geoTransform);

GDALRasterBand* rasterBand = dem->GetRasterBand(1);

nCols = rasterBand->GetXSize();
nRows = rasterBand->GetYSize();
noData = rasterBand->GetNoDataValue();

//rasterBand->GetBlockSize(&nBlockXSize, &nBlockYSize);

int nXBlocks = (rasterBand->GetXSize() + readCols - 1) / readCols;
int nYBlocks = (rasterBand->GetYSize() + readRows - 1) / readRows;

cout << nYBlocks << "___" << nXBlocks << "\n";


//Slope
GDALDataset *slope = gTIF->Create("path/slopeBlock.tif", nCols, nRows, 1, GDT_Float32, NULL);
slope->SetGeoTransform(geoTransform);

for (int i = 0; i < nYBlocks; i++)
{
    for (int j = 0; j < nXBlocks; j++)
    {
        float* rasterBlock = (float*)CPLMalloc(readCols*readRows*sizeof(float));
        float* rasterBlockOut = (float*)CPLMalloc(readCols*readRows*sizeof(float));

        if (rasterBand != nullptr)
            rasterBand->RasterIO(GDALRWFlag::GF_Read, j * readCols, i * readRows, readCols, readRows, rasterBlock, readCols, readRows, GDALDataType::GDT_CFloat32, 0, 0);

        //Not sure if is working
        for (int jb = 0; jb < readCols; jb++)
        {
            if (rasterBlock[jb] == noData)
            {
                rasterBlockOut[jb] = noData;
            }
            else
            {
                rasterBlockOut[jb] = rasterBlock[jb];
            }
        }

        slope->GetRasterBand(1)->RasterIO(GDALRWFlag::GF_Write, j * readCols, i * readRows, readCols, readRows, rasterBlockOut, readCols, readRows, GDALDataType::GDT_CFloat32, 0, 0);

        CPLFree(rasterBlock);
        CPLFree(rasterBlockOut);
    }
}

GDALClose(dem);
GDALClose(slope);

Answer 1

这可能不是崩溃的原因，但即使您的图像较小，您也要求 2048*2048 block 。此代码应仅适用于大小为 2048 的倍数的图像。

你应该这样做:

nXSize = min(readCols, rasterBand->GetXSize() - j * readCols);
nYSize = min(readRows, rasterBand->GetYSize() - i * readRows);

rasterBand->RasterIO(GDALRWFlag::GF_Read, j * readCols, i * readRows, 
    nXSize, nYSize, rasterBlock, nXSize, nYSize, GDALDataType::GDT_CFloat32, 0, 0);