From 913f53a53f55f02f4091f989f984f53fff23bf8c Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Mon, 19 Aug 2019 09:16:12 +1000
Subject: [PATCH] [FEATURE] Add option to simplify geometries when exporting
 canvas to PDF

Reduces output file size by removing redundant vertices given export
DPI settings
---
 src/app/qgsmapsavedialog.cpp | 12 ++++++++++++
 src/ui/qgsmapsavedialog.ui   | 22 ++++++++++++++++------
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/src/app/qgsmapsavedialog.cpp b/src/app/qgsmapsavedialog.cpp
index feaf15651de0..566c542f6b08 100644
--- a/src/app/qgsmapsavedialog.cpp
+++ b/src/app/qgsmapsavedialog.cpp
@@ -137,6 +137,7 @@ QgsMapSaveDialog::QgsMapSaveDialog( QWidget *parent, QgsMapCanvas *mapCanvas, co
     case Image:
     {
       mGeoPDFGroupBox->hide();
+      mSimplifyGeometriesCheckbox->hide();
       QPushButton *button = new QPushButton( tr( "Copy to Clipboard" ) );
       buttonBox->addButton( button, QDialogButtonBox::ResetRole );
       connect( button, &QPushButton::clicked, this, &QgsMapSaveDialog::copyToClipboard );
@@ -474,6 +475,17 @@ void QgsMapSaveDialog::onAccepted()
         QgsMapSettings ms = QgsMapSettings();
         applyMapSettings( ms );
 
+        if ( mSimplifyGeometriesCheckbox->isChecked() )
+        {
+          QgsVectorSimplifyMethod simplifyMethod;
+          simplifyMethod.setSimplifyHints( QgsVectorSimplifyMethod::GeometrySimplification );
+          simplifyMethod.setForceLocalOptimization( true );
+          // we use SnappedToGridGlobal, because it avoids gaps and slivers between previously adjacent polygons
+          simplifyMethod.setSimplifyAlgorithm( QgsVectorSimplifyMethod::SnappedToGridGlobal );
+          simplifyMethod.setThreshold( 0.1f ); // (pixels). We are quite conservative here. This could possibly be bumped all the way up to 1. But let's play it safe.
+          ms.setSimplifyMethod( simplifyMethod );
+        }
+
         QgsAbstractGeoPdfExporter::ExportDetails geoPdfExportDetails;
         if ( mGeoPDFGroupBox->isChecked() )
         {
diff --git a/src/ui/qgsmapsavedialog.ui b/src/ui/qgsmapsavedialog.ui
index 07cc9c5c32f6..6c851a85b572 100644
--- a/src/ui/qgsmapsavedialog.ui
+++ b/src/ui/qgsmapsavedialog.ui
@@ -15,7 +15,7 @@
   </property>
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
-    <layout class="QGridLayout" name="gridLayout" rowstretch="0,0,0,0,0,0,0,0,0,0,0">
+    <layout class="QGridLayout" name="gridLayout" rowstretch="0,0,0,0,0,0,0,0,0,0,0,0">
      <item row="2" column="0">
       <widget class="QLabel" name="label_2">
        <property name="text">
@@ -43,7 +43,7 @@
        </property>
       </widget>
      </item>
-     <item row="8" column="0" colspan="2">
+     <item row="9" column="0" colspan="2">
       <widget class="QGroupBox" name="mGeoPDFGroupBox">
        <property name="title">
         <string>Create Geospatial PDF (GeoPDF)</string>
@@ -97,7 +97,7 @@
             <property name="bottomMargin">
              <number>0</number>
             </property>
-            <item row="1" column="0">
+            <item row="2" column="0">
              <spacer name="verticalSpacer">
               <property name="orientation">
                <enum>Qt::Vertical</enum>
@@ -105,7 +105,7 @@
               <property name="sizeHint" stdset="0">
                <size>
                 <width>20</width>
-                <height>133</height>
+                <height>102</height>
                </size>
               </property>
              </spacer>
@@ -158,7 +158,7 @@
        </property>
       </widget>
      </item>
-     <item row="9" column="0" colspan="2">
+     <item row="10" column="0" colspan="2">
       <widget class="QCheckBox" name="mSaveAsRaster">
        <property name="visible">
         <bool>false</bool>
@@ -287,13 +287,23 @@ Rasterizing the map is recommended when such effects are used.</string>
        </property>
       </widget>
      </item>
-     <item row="10" column="0" colspan="2">
+     <item row="11" column="0" colspan="2">
       <widget class="QLabel" name="mInfo">
        <property name="enabled">
         <bool>false</bool>
        </property>
       </widget>
      </item>
+     <item row="8" column="0" colspan="2">
+      <widget class="QCheckBox" name="mSimplifyGeometriesCheckbox">
+       <property name="text">
+        <string>Simplify geometries to reduce output file size</string>
+       </property>
+       <property name="checked">
+        <bool>true</bool>
+       </property>
+      </widget>
+     </item>
     </layout>
    </item>
    <item>