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Merge pull request #27919 from Kumataro:fix27830

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imgcodecs: Workaround for image flipping bug in older GDAL FITS drivers
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Alexander Smorkalov 2025-10-20 15:18:25 +03:00 committed by GitHub
commit fa276bba3d
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1 changed files with 13 additions and 3 deletions
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16
modules/imgcodecs/src/grfmt_gdal.cpp
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@ -425,8 +425,18 @@ bool GdalDecoder::readData( Mat& img ){
// create a temporary scanline pointer to store data
double* scanline = new double[nCols];
#if GDAL_VERSION_NUM < GDAL_COMPUTE_VERSION(3,3,0)
// FITS drivers on version GDAL prior to v3.3.0 return vertically mirrored results.
// See https://github.com/OSGeo/gdal/pull/3520
// See https://github.com/OSGeo/gdal/commit/ef0f86696d163e065943b27f50dcff77790a1311
const bool isNeedVerticallyFlip = strncmp(m_dataset->GetDriverName(), "FITS", 4) == 0;
#else
const bool isNeedVerticallyFlip = false;
#endif
// iterate over each row and column
for( int y=0; y<nRows; y++ ){
for( int y=0; y<nRows; y++ ){ // for GDAL
const int yCv = isNeedVerticallyFlip ? (nRows - 1) - y : y ; // for OpenCV
// get the entire row
CPLErr err = band->RasterIO( GF_Read, 0, y, nCols, 1, scanline, nCols, 1, GDT_Float64, 0, 0);
@ -438,10 +448,10 @@ bool GdalDecoder::readData( Mat& img ){
// set depending on image types
// given boost, I would use enable_if to speed up. Avoid for now.
if( hasColorTable == false ){
write_pixel( scanline[x], gdalType, nChannels, img, y, x, color );
write_pixel( scanline[x], gdalType, nChannels, img, yCv, x, color );
}
else{
write_ctable_pixel( scanline[x], gdalType, gdalColorTable, img, y, x, color );
write_ctable_pixel( scanline[x], gdalType, gdalColorTable, img, yCv, x, color );
}
}
}