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Řádek 1: |
| {{Upravit}} | | {{freegiswiki|GDAL / Ukázka použití}} |
| Tato stránka obsahuje ukázku zdrojového textu demonstračního programu využívající pro přístup k rastrovým datům knihovnu '''[[GDAL/OGR|GDAL]]'''. Program počítá [http://en.wikipedia.org/wiki/Normalized_Difference_Vegetation_Index normalizovaný vegetační index], více informace na cvičení předmětu [[153YZOD Zpracování obrazových dat - cvičení 4#Podíl obrazu|Zpracování obrazových dat]].
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| <center>
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| <math>
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| ndvi = \frac{(tm4 - tm3)}{(tm4 + tm3)}
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| </math>
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| </center>
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| kde <tt>tm4</tt> je 4. kanál družicové scény Landsat TM, <tt>tm3</tt> je kanál třetí.
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| __TOC__
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| == C++ ==
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| <source lang="cpp">
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| #include <iostream>
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| #include "gdal_priv.h"
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| using std::cout;
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| using std::cerr;
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| using std::endl;
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|
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| GDALDataset *open_file(const char *filename)
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| {
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| GDALDataset *poDs;
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|
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| poDs = (GDALDataset *) GDALOpen(filename, GA_ReadOnly);
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| if (poDs == NULL) {
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| cerr << "Otevreni '" << filename << "' selhalo." << endl;
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| return NULL;
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| }
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|
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| return poDs;
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| }
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| int calculate_ndvi(GDALDataset *poDsNdvi, GDALDataset *poDsTm3, GDALDataset *poDsTm4)
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| {
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| GDALRasterBand *poBandNdvi, *poBandTm3, *poBandTm4;
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|
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| poBandNdvi = poDsNdvi->GetRasterBand(1);
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| poBandTm3 = poDsTm3->GetRasterBand(1);
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| poBandTm4 = poDsTm4->GetRasterBand(1);
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| if (!poBandNdvi || !poBandTm3 || !poBandTm4)
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| return -1;
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| unsigned char *pafScanlineTm3, *pafScanlineTm4;
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| double *pafScanlineNdvi;
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| int nXSize = poBandTm3->GetXSize();
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| int nYSize = poBandTm3->GetYSize();
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| if (nXSize != poBandTm4->GetXSize() ||
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| nYSize != poBandTm4->GetYSize())
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| return -1;
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| pafScanlineTm3 = (unsigned char *) CPLMalloc(sizeof(unsigned char) * nXSize);
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| pafScanlineTm4 = (unsigned char *) CPLMalloc(sizeof(unsigned char) * nXSize);
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| pafScanlineNdvi = (double *) CPLMalloc(sizeof(double) * nXSize);
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| for (int row = 0; row < nYSize; row++) {
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| poBandTm3->RasterIO(GF_Read, 0, row, nXSize, 1,
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| pafScanlineTm3, nXSize, 1, GDT_Byte,
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| 0, 0);
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| poBandTm4->RasterIO(GF_Read, 0, row, nXSize, 1,
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| pafScanlineTm4, nXSize, 1, GDT_Byte,
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| 0, 0);
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|
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| for (int col = 0; col < nXSize; col++) {
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| pafScanlineNdvi[col] = double(pafScanlineTm4[col] - pafScanlineTm3[col]) /
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| (pafScanlineTm4[col] + pafScanlineTm3[col]);
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| }
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| poBandNdvi->RasterIO(GF_Write, 0, row, nXSize, 1,
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| pafScanlineNdvi, nXSize, 1, GDT_Float32,
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| 0, 0);
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| }
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|
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| CPLFree(pafScanlineTm3);
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| CPLFree(pafScanlineTm4);
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| CPLFree(pafScanlineNdvi);
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| return 0;
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| }
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| int main(int argc, char **argv)
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| {
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| const char *filenameTm3, *filenameTm4;
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|
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| double trans[6];
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| GDALDriver *poDriver;
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| GDALDataset *poDsTm3, *poDsTm4, *poDsNdvi;
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|
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| if (argc != 3) {
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| cerr << "Pouziti: " << argv[0] << " tm3 tm4" << endl;
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| return 1;
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| }
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|
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| filenameTm3 = argv[1];
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| filenameTm4 = argv[2];
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| // registrovat dostupne GDAL ovladace
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| GDALAllRegister();
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|
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| // otevrit rastrove soubory 'tm3' a 'tm4' pro cteni
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| poDsTm3 = open_file(filenameTm3);
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| poDsTm4 = open_file(filenameTm4);
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| if (poDsTm3 == NULL || poDsTm4 == NULL)
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| return 1;
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| poDriver = poDsTm3->GetDriver();
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| poDsNdvi = poDriver->Create("ndvi.tif", poDsTm3->GetRasterXSize(), poDsTm3->GetRasterYSize(),
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| 1, GDT_Float32, NULL);
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| poDsTm3->GetGeoTransform(trans);
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| poDsNdvi->SetGeoTransform(trans);
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| poDsNdvi->SetProjection(poDsTm3->GetProjectionRef());
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|
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| if (poDsNdvi == NULL)
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| cerr << "Nelze vytvorit vystupni soubor 'ndvi.tif'" << endl;
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| if (calculate_ndvi(poDsNdvi, poDsTm3, poDsTm4) != 0)
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| cerr << "Nelze vypocitat NDVI" << endl;
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| GDALClose(poDsTm3);
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| GDALClose(poDsTm4);
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| GDALClose(poDsNdvi);
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|
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| return 0;
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| }
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| </source>
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| == Python ==
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| <source lang="python">
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| @TODO
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| </source>
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| == Související články ==
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| * [[Programování s knihovnou OGR]]
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| * [[153GIS2 - 10. cvičení - GRASS GIS|Ukázka skriptů pro GRASS GIS]]
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| == Externí odkazy ==
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| * [http://gdal.osgeo.org/gdal_datamodel.html GDAL Data Model]
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| * [http://gdal.osgeo.org/hierarchy.html API Reference Documentation]
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| * [http://gdal.osgeo.org/gdal_tutorial.html GDAL API Tutorial]
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| * [http://gdal.osgeo.org/gdal_drivertut.html GDAL Driver Implementation Tutorial]
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| * [http://trac.osgeo.org/gdal/wiki/rfc8_devguide RFC 8: Developer Guidelines]
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| {{GFOSS}}
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| {{Programování}}
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| {{C++}}
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| {{Python}}
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