vcl: add unit test for certain sizes of bitmaps to be dithered

Change-Id: I9e40c8536c86468040bde56c569e7c69ad8f745b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/107947
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

1 files changed, 34 insertions, 1 deletions

diff --git a/vcl/qa/cppunit/BitmapTest.cxx b/vcl/qa/cppunit/BitmapTest.cxx
index 67f897cd9ef4..8a931df524eb 100644
--- a/vcl/qa/cppunit/BitmapTest.cxx
+++ b/vcl/qa/cppunit/BitmapTest.cxx
@@ -1,4 +1,3 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /*
  * This file is part of the LibreOffice project.
  *
@@ -46,6 +45,7 @@ class BitmapTest : public CppUnit::TestFixture
     void testBitmap32();
     void testOctree();
     void testEmptyAccess();
+    void testDitherSize();
 
     CPPUNIT_TEST_SUITE(BitmapTest);
     CPPUNIT_TEST(testCreation);
@@ -61,6 +61,7 @@ class BitmapTest : public CppUnit::TestFixture
     CPPUNIT_TEST(testBitmap32);
     CPPUNIT_TEST(testOctree);
     CPPUNIT_TEST(testEmptyAccess);
+    CPPUNIT_TEST(testDitherSize);
     CPPUNIT_TEST_SUITE_END();
 };
 
@@ -650,6 +651,38 @@ void BitmapTest::testEmptyAccess()
     CPPUNIT_ASSERT_EQUAL(tools::Long(0), access.Height());
 }
 
+void BitmapTest::testDitherSize()
+{
+    // no need to do anything for a 1x1 pixel bitmap
+    {
+        Bitmap aBitmap(Size(1, 1), 24);
+        CPPUNIT_ASSERT(aBitmap.Dither());
+    }
+
+    // cannot dither a bitmap with a width of 2 or 3 pixels
+    {
+        Bitmap aBitmap(Size(2, 4), 24);
+        CPPUNIT_ASSERT(!aBitmap.Dither());
+    }
+
+    {
+        Bitmap aBitmap(Size(3, 4), 24);
+        CPPUNIT_ASSERT(!aBitmap.Dither());
+    }
+
+    // cannot dither a bitmap with a height of 2 pixels
+    {
+        Bitmap aBitmap(Size(4, 2), 24);
+        CPPUNIT_ASSERT(!aBitmap.Dither());
+    }
+
+    // only dither bitmaps with a width > 3 pixels and height > 2 pixels
+    {
+        Bitmap aBitmap(Size(4, 3), 24);
+        CPPUNIT_ASSERT(aBitmap.Dither());
+    }
+}
+
 } // namespace
 
 CPPUNIT_TEST_SUITE_REGISTRATION(BitmapTest);