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CLI: Add gdal vector dissolve
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‎apps/CMakeLists.txt‎

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@@ -103,6 +103,7 @@ target_sources(appslib PRIVATE
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gdalalg_vector_collect.cpp
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gdalalg_vector_concat.cpp
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gdalalg_vector_convert.cpp
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gdalalg_vector_dissolve.cpp
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gdalalg_vector_edit.cpp
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gdalalg_vector_pipeline.cpp
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gdalalg_vector_rasterize.cpp

‎apps/gdalalg_vector.cpp‎

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#include "gdalalg_vector_collect.h"
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#include "gdalalg_vector_concat.h"
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#include "gdalalg_vector_convert.h"
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#include "gdalalg_vector_dissolve.h"
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#include "gdalalg_vector_edit.h"
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#include "gdalalg_vector_explode_collections.h"
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#include "gdalalg_vector_geom.h"
@@ -77,6 +78,7 @@ class GDALVectorAlgorithm final : public GDALAlgorithm
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RegisterSubAlgorithm<GDALVectorCollectAlgorithmStandalone>();
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RegisterSubAlgorithm<GDALVectorConcatAlgorithmStandalone>();
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RegisterSubAlgorithm<GDALVectorConvertAlgorithm>();
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RegisterSubAlgorithm<GDALVectorDissolveAlgorithmStandalone>();
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RegisterSubAlgorithm<GDALVectorEditAlgorithmStandalone>();
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RegisterSubAlgorithm<GDALVectorExplodeCollectionsAlgorithmStandalone>();
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RegisterSubAlgorithm<GDALVectorGridAlgorithmStandalone>();

‎apps/gdalalg_vector_dissolve.cpp‎

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/******************************************************************************
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*
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* Project: GDAL
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* Purpose: "gdal vector dissolve"
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* Author: Dan Baston
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*
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******************************************************************************
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* Copyright (c) 2025, ISciences LLC
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*
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* SPDX-License-Identifier: MIT
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****************************************************************************/
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#include "gdalalg_vector_dissolve.h"
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#include "gdal_priv.h"
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#include "ogrsf_frmts.h"
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//! @cond Doxygen_Suppress
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#ifndef _
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#define _(x) (x)
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#endif
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/************************************************************************/
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/* GDALVectorDissolveAlgorithm() */
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/************************************************************************/
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GDALVectorDissolveAlgorithm::GDALVectorDissolveAlgorithm(bool standaloneStep)
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: GDALVectorGeomAbstractAlgorithm(NAME, DESCRIPTION, HELP_URL,
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standaloneStep, m_opts)
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{
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}
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#ifdef HAVE_GEOS
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namespace
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{
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/************************************************************************/
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/* GDALVectorDissolveAlgorithmLayer */
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/************************************************************************/
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class GDALVectorDissolveAlgorithmLayer final
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: public GDALVectorGeomOneToOneAlgorithmLayer<GDALVectorDissolveAlgorithm>
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{
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public:
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GDALVectorDissolveAlgorithmLayer(
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OGRLayer &oSrcLayer, const GDALVectorDissolveAlgorithm::Options &opts)
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: GDALVectorGeomOneToOneAlgorithmLayer<GDALVectorDissolveAlgorithm>(
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oSrcLayer, opts)
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{
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}
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protected:
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using GDALVectorGeomOneToOneAlgorithmLayer::TranslateFeature;
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std::unique_ptr<OGRFeature>
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TranslateFeature(std::unique_ptr<OGRFeature> poSrcFeature) const override;
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private:
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};
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/************************************************************************/
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/* TranslateFeature() */
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/************************************************************************/
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std::unique_ptr<OGRFeature> GDALVectorDissolveAlgorithmLayer::TranslateFeature(
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std::unique_ptr<OGRFeature> poSrcFeature) const
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{
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const int nGeomFieldCount = poSrcFeature->GetGeomFieldCount();
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for (int i = 0; i < nGeomFieldCount; ++i)
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{
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if (IsSelectedGeomField(i))
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{
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if (auto poGeom = std::unique_ptr<OGRGeometry>(
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poSrcFeature->StealGeometry(i)))
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{
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poGeom.reset(poGeom->UnaryUnion());
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if (poGeom)
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{
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poGeom->assignSpatialReference(m_srcLayer.GetLayerDefn()
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->GetGeomFieldDefn(i)
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->GetSpatialRef());
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poSrcFeature->SetGeomField(i, std::move(poGeom));
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}
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}
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}
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}
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return poSrcFeature;
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}
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} // namespace
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#endif // HAVE_GEOS
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/************************************************************************/
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/* GDALVectorDissolveAlgorithm::CreateAlgLayer() */
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/************************************************************************/
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std::unique_ptr<OGRLayerWithTranslateFeature>
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GDALVectorDissolveAlgorithm::CreateAlgLayer([[maybe_unused]] OGRLayer &srcLayer)
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{
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#ifdef HAVE_GEOS
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return std::make_unique<GDALVectorDissolveAlgorithmLayer>(srcLayer, m_opts);
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#else
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CPLAssert(false);
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return nullptr;
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#endif
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}
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/************************************************************************/
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/* GDALVectorDissolveAlgorithm::RunStep() */
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/************************************************************************/
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bool GDALVectorDissolveAlgorithm::RunStep(GDALPipelineStepRunContext &ctxt)
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{
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#ifdef HAVE_GEOS
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return GDALVectorGeomAbstractAlgorithm::RunStep(ctxt);
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#else
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(void)ctxt;
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ReportError(CE_Failure, CPLE_NotSupported,
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"This algorithm is only supported for builds against GEOS");
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return false;
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#endif
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}
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GDALVectorDissolveAlgorithmStandalone::
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~GDALVectorDissolveAlgorithmStandalone() = default;
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//! @endcond

‎apps/gdalalg_vector_dissolve.h‎

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/******************************************************************************
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*
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* Project: GDAL
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* Purpose: "gdal vector dissolve"
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* Author: Daniel Baston
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*
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******************************************************************************
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* Copyright (c) 2025, ISciences LLC
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*
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* SPDX-License-Identifier: MIT
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****************************************************************************/
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#ifndef GDALALG_VECTOR_DISSOLVE_INCLUDED
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#define GDALALG_VECTOR_DISSOLVE_INCLUDED
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#include "gdalalg_vector_geom.h"
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#include "cpl_progress.h"
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#include <string>
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//! @cond Doxygen_Suppress
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/************************************************************************/
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/* GDALVectorDissolveAlgorithm */
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/************************************************************************/
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class GDALVectorDissolveAlgorithm : public GDALVectorGeomAbstractAlgorithm
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{
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public:
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static constexpr const char *NAME = "dissolve";
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static constexpr const char *DESCRIPTION = "Dissolves multipart features";
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static constexpr const char *HELP_URL =
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"/programs/gdal_vector_dissolve.html";
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explicit GDALVectorDissolveAlgorithm(bool standaloneStep = false);
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std::unique_ptr<OGRLayerWithTranslateFeature>
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CreateAlgLayer(OGRLayer &srcLayer) override;
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struct Options : OptionsBase
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{
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};
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private:
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bool RunStep(GDALPipelineStepRunContext &ctxt) override;
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Options m_opts{};
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};
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/************************************************************************/
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/* GDALVectorDissolveAlgorithmStandalone */
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/************************************************************************/
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class GDALVectorDissolveAlgorithmStandalone final
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: public GDALVectorDissolveAlgorithm
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{
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public:
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GDALVectorDissolveAlgorithmStandalone()
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: GDALVectorDissolveAlgorithm(/* standaloneStep = */ true)
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{
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}
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~GDALVectorDissolveAlgorithmStandalone() override;
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};
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//! @endcond
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#endif /* GDALALG_VECTOR_DISSOLVE_INCLUDED */

‎apps/gdalalg_vector_pipeline.cpp‎

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#include "gdalalg_vector_clip.h"
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#include "gdalalg_vector_collect.h"
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#include "gdalalg_vector_concat.h"
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#include "gdalalg_vector_dissolve.h"
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#include "gdalalg_vector_edit.h"
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#include "gdalalg_vector_explode_collections.h"
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#include "gdalalg_vector_filter.h"
@@ -154,6 +155,7 @@ void GDALVectorPipelineAlgorithm::RegisterAlgorithms(
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registry.Register<GDALVectorClipAlgorithm>(
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addSuffixIfNeeded(GDALVectorClipAlgorithm::NAME));
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registry.Register<GDALVectorDissolveAlgorithm>();
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registry.Register<GDALVectorEditAlgorithm>(
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addSuffixIfNeeded(GDALVectorEditAlgorithm::NAME));

‎autotest/utilities/test_gdalalg_vector_dissolve.py‎

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#!/usr/bin/env pytest
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# -*- coding: utf-8 -*-
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###############################################################################
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# Project: GDAL/OGR Test Suite
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# Purpose: 'gdal vector dissolve' testing
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# Author: Daniel Baston
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#
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###############################################################################
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# Copyright (c) 2025, ISciences LLC
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#
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# SPDX-License-Identifier: MIT
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###############################################################################
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import gdaltest
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import pytest
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from osgeo import gdal, ogr
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@pytest.fixture()
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def alg():
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return gdal.GetGlobalAlgorithmRegistry()["vector"]["dissolve"]
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pytestmark = pytest.mark.require_geos
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@pytest.mark.parametrize(
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"wkt_in,wkt_out",
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[
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["MULTIPOINT (3 3, 4 4, 3 3)", "MULTIPOINT (3 3, 4 4)"],
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[
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"MULTIPOLYGON (((0 0, 1 0, 1 1, 0 0)), ((0 0, 1 1, 0 1, 0 0)))",
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"POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0))",
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],
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[
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"MULTILINESTRING ((0 0, 1 1), (1 1, 2 2), (1 0, 0 1))",
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"MULTILINESTRING ((0 0, 0.5 0.5), (0.5 0.5, 1 1), (1 1, 2 2), (1 0, 0.5 0.5), (0.5 0.5, 0 1))",
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],
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],
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)
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def test_gdalalg_vector_dissolve(alg, wkt_in, wkt_out):
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if type(wkt_in) is str:
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wkt_in = [wkt_in]
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if type(wkt_out) is str:
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wkt_out = [wkt_out]
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alg["input"] = gdaltest.wkt_ds(wkt_in)
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alg["output"] = ""
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alg["output-format"] = "stream"
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assert alg.Run()
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dst_ds = alg["output"].GetDataset()
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dst_lyr = dst_ds.GetLayer(0)
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assert dst_lyr.GetFeatureCount() == len(wkt_out)
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for f, expected_wkt in zip(dst_lyr, wkt_out):
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g1 = f.GetGeometryRef().Normalize()
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g2 = ogr.CreateGeometryFromWkt(expected_wkt).Normalize()
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assert g1.Equals(g2)

‎doc/source/conf.py‎

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[author_evenr],
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1,
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),
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(
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"programs/gdal_vector_dissolve",
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"gdal-vector-dissolve",
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"Unions the elmeents of each feature's geometry.",
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[author_dbaston],
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1,
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),
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(
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"programs/gdal_vector_edit",
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"gdal-vector-edit",

‎doc/source/programs/gdal_vector_dissolve.rst‎

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.. _gdal_vector_dissolve:
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================================================================================
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``gdal vector dissolve``
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================================================================================
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.. versionadded:: 3.13
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.. only:: html
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Unions the elements of each feature's geometry.
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.. Index:: gdal vector dissolve
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Synopsis
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--------
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.. program-output:: gdal vector dissolve --help-doc
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Description
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-----------
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:program:`gdal vector dissolve` performs a union operation on the elements of each feature's geometry. This has the following effects:
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- Duplicate vertices are eliminated.
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- Nodes are added where input linework intersects.
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- Polygons that overlap are "dissolved" into a single feature.
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``dissolve`` can be used as a step of :ref:`gdal_vector_pipeline`.

‎doc/source/programs/index.rst‎

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gdal_vector_collect
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gdal_vector_concat
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gdal_vector_convert
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gdal_vector_dissolve
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gdal_vector_edit
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gdal_vector_filter
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gdal_vector_info

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