Use QgsRenderChecker to compare png images when comparing processing result

directories

python/core/auto_generated/qgsrenderchecker.sip.in

@@ -165,6 +165,13 @@ Test using two arbitrary images (map renderer will not be used)
                       for that by providing a tolerance.
 :param renderedImageFile: to optionally override the output filename
 \note: make sure to call setExpectedImage and setRenderedImage first.
+%End
+
+    bool compareImages( const QString &testName, const QString &referenceImageFile, const QString &renderedImageFile, unsigned int mismatchCount = 0 );
+%Docstring
+Test using two arbitrary images at the specified paths for equality.
+
+.. versionadded:: 3.18
 %End
 
     bool isKnownAnomaly( const QString &diffImageFile );

python/testing/__init__.py

@@ -35,7 +35,8 @@ from qgis.core import (
     QgsFeatureRequest,
     QgsCoordinateReferenceSystem,
     NULL,
-    QgsVectorLayer
+    QgsVectorLayer,
+    QgsRenderChecker
 )
 
 import unittest
@@ -226,21 +227,28 @@ class TestCase(_TestCase):
 
         contents_result = list(path_result.iterdir())
         contents_expected = list(path_expected.iterdir())
+        contents_expected = [p for p in contents_expected if p.suffix != '.png' or not p.stem.endswith('_mask')]
         self.assertCountEqual([p.name if p.is_file() else p.stem for p in contents_expected], [p.name if p.is_file() else p.stem for p in contents_result], f'Directory contents mismatch in {dirpath_expected} vs {dirpath_result}')
 
         # compare file contents
-        for expected_file_path in path_expected.iterdir():
+        for expected_file_path in contents_expected:
             if expected_file_path.is_dir():
                 continue
 
             result_file_path = path_result / expected_file_path.name
 
             if expected_file_path.suffix == '.pbf':
+                # vector layer, use assertLayersEqual
                 layer_expected = QgsVectorLayer(str(expected_file_path), 'Expected')
                 self.assertTrue(layer_expected.isValid())
                 layer_result = QgsVectorLayer(str(result_file_path), 'Result')
                 self.assertTrue(layer_result.isValid())
                 self.assertLayersEqual(layer_expected, layer_result)
+            elif expected_file_path.suffix == '.png':
+                # image file, use QgsRenderChecker
+                checker = QgsRenderChecker()
+                res = checker.compareImages(expected_file_path.stem, expected_file_path.as_posix(), result_file_path.as_posix())
+                self.assertTrue(res)
             else:
                 assert False, f"Don't know how to compare {expected_file_path.suffix} files"
 

src/core/qgsrenderchecker.cpp

@@ -251,6 +251,12 @@ bool QgsRenderChecker::compareImages( const QString &testName,
               "Image File not set.</td></tr></table>\n";
     return false;
   }
+
+  return compareImages( testName, mExpectedImageFile, renderedImageFile, mismatchCount );
+}
+
+bool QgsRenderChecker::compareImages( const QString &testName, const QString &referenceImageFile, const QString &renderedImageFile, unsigned int mismatchCount )
+{
   if ( ! renderedImageFile.isEmpty() )
   {
     mRenderedImageFile = renderedImageFile;
@@ -272,7 +278,7 @@ bool QgsRenderChecker::compareImages( const QString &testName,
   //
   // Load /create the images
   //
-  QImage myExpectedImage( mExpectedImageFile );
+  QImage myExpectedImage( referenceImageFile );
   QImage myResultImage( mRenderedImageFile );
   if ( myResultImage.isNull() )
   {
@@ -290,7 +296,7 @@ bool QgsRenderChecker::compareImages( const QString &testName,
   myDifferenceImage.fill( qRgb( 152, 219, 249 ) );
 
   //check for mask
-  QString maskImagePath = mExpectedImageFile;
+  QString maskImagePath = referenceImageFile;
   maskImagePath.chop( 4 ); //remove .png extension
   maskImagePath += QLatin1String( "_mask.png" );
   const QImage maskImage( maskImagePath );
@@ -343,7 +349,7 @@ bool QgsRenderChecker::compareImages( const QString &testName,
                            .arg( testName,
                                  myDiffImageFile,
                                  mRenderedImageFile,
-                                 mExpectedImageFile )
+                                 referenceImageFile )
                            .arg( imgWidth ).arg( imgHeight )
                            .arg( QUuid::createUuid().toString().mid( 1, 6 ) );
 
@@ -356,7 +362,7 @@ bool QgsRenderChecker::compareImages( const QString &testName,
   // To get the images into CDash
   //
   emitDashMessage( "Rendered Image " + testName + prefix, QgsDartMeasurement::ImagePng, mRenderedImageFile );
-  emitDashMessage( "Expected Image " + testName + prefix, QgsDartMeasurement::ImagePng, mExpectedImageFile );
+  emitDashMessage( "Expected Image " + testName + prefix, QgsDartMeasurement::ImagePng, referenceImageFile );
 
   //
   // Put the same info to debug too
@@ -524,7 +530,7 @@ bool QgsRenderChecker::compareImages( const QString &testName,
                    "you can do something like this\n"
                    "cp '" + myDiffImageFile + "' " + controlImagePath() + mControlName +
                    "/\nIf it should be included in the mask run\n"
-                   "scripts/generate_test_mask_image.py '" + mExpectedImageFile + "' '" + mRenderedImageFile + "'\n" );
+                   "scripts/generate_test_mask_image.py '" + referenceImageFile + "' '" + mRenderedImageFile + "'\n" );
 
   mReport += QLatin1String( "<tr><td colspan = 3>\n" );
   mReport += "<font color=red>Test image and result image for " + testName + " are mismatched</font><br>";

src/core/qgsrenderchecker.h

@@ -170,6 +170,13 @@ class CORE_EXPORT QgsRenderChecker
      */
     bool compareImages( const QString &testName, unsigned int mismatchCount = 0, const QString &renderedImageFile = QString() );
 
+    /**
+     * Test using two arbitrary images at the specified paths for equality.
+     *
+     * \since QGIS 3.18
+     */
+    bool compareImages( const QString &testName, const QString &referenceImageFile, const QString &renderedImageFile, unsigned int mismatchCount = 0 );
+
     /**
      * Gets a list of all the anomalies. An anomaly is a rendered difference
      * file where there is some red pixel content (indicating a render check