ImageViewer: Allow choice between nearest neighbor and bilinear scaling

Currently, ImageViewer always uses nearest neighbor scaling.
This allows the user to choose whether to use nearest neighbor
or bilinear scaling. It current defaults to nearest neighbor.

Userland/Applications/ImageViewer/ViewWidget.cpp

@@ -14,7 +14,6 @@
 #include <LibCore/MappedFile.h>
 #include <LibCore/Timer.h>
 #include <LibGUI/MessageBox.h>
-#include <LibGUI/Painter.h>
 #include <LibGfx/Bitmap.h>
 #include <LibGfx/Orientation.h>
 #include <LibGfx/Palette.h>
@@ -178,7 +177,7 @@ void ViewWidget::paint_event(GUI::PaintEvent& event)
     Gfx::StylePainter::paint_transparency_grid(painter, frame_inner_rect(), palette());
 
     if (!m_bitmap.is_null())
-        painter.draw_scaled_bitmap(m_bitmap_rect, *m_bitmap, m_bitmap->rect());
+        painter.draw_scaled_bitmap(m_bitmap_rect, *m_bitmap, m_bitmap->rect(), 1.0f, m_scaling_mode);
 }
 
 void ViewWidget::mousedown_event(GUI::MouseEvent& event)
@@ -343,4 +342,10 @@ void ViewWidget::animate()
     }
 }
 
+void ViewWidget::set_scaling_mode(Gfx::Painter::ScalingMode scaling_mode)
+{
+    m_scaling_mode = scaling_mode;
+    update();
+}
+
 }

Userland/Applications/ImageViewer/ViewWidget.h

@@ -10,6 +10,7 @@
 
 #include <LibCore/Timer.h>
 #include <LibGUI/Frame.h>
+#include <LibGUI/Painter.h>
 #include <LibGfx/Point.h>
 #include <LibImageDecoderClient/Client.h>
 
@@ -37,6 +38,7 @@ public:
     void set_scaled_for_first_image(bool val) { m_scaled_for_first_image = val; }
     void set_path(const String& path);
     void resize_window();
+    void set_scaling_mode(Gfx::Painter::ScalingMode);
 
     bool is_next_available() const;
     bool is_previous_available() const;
@@ -86,6 +88,7 @@ private:
     Gfx::FloatPoint m_saved_pan_origin;
     Vector<String> m_files_in_same_dir;
     Optional<size_t> m_current_index;
+    Gfx::Painter::ScalingMode m_scaling_mode { Gfx::Painter::ScalingMode::NearestNeighbor };
 };
 
 }

Userland/Applications/ImageViewer/main.cpp

@@ -11,6 +11,7 @@
 #include <LibCore/System.h>
 #include <LibDesktop/Launcher.h>
 #include <LibGUI/Action.h>
+#include <LibGUI/ActionGroup.h>
 #include <LibGUI/Application.h>
 #include <LibGUI/BoxLayout.h>
 #include <LibGUI/Clipboard.h>
@@ -225,6 +226,16 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         if (widget.bitmap())
             GUI::Clipboard::the().set_bitmap(*widget.bitmap());
     });
+
+    auto nearest_neighbor_action = GUI::Action::create_checkable("&Nearest Neighbor", [&](auto&) {
+        widget.set_scaling_mode(Gfx::Painter::ScalingMode::NearestNeighbor);
+    });
+    nearest_neighbor_action->set_checked(true);
+
+    auto bilinear_action = GUI::Action::create_checkable("&Bilinear", [&](auto&) {
+        widget.set_scaling_mode(Gfx::Painter::ScalingMode::BilinearBlend);
+    });
+
     widget.on_image_change = [&](const Gfx::Bitmap* bitmap) {
         bool should_enable_image_actions = (bitmap != nullptr);
         bool should_enable_forward_actions = (widget.is_next_available() && should_enable_image_actions);
@@ -287,6 +298,18 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     view_menu.add_action(zoom_in_action);
     view_menu.add_action(reset_zoom_action);
     view_menu.add_action(zoom_out_action);
+    view_menu.add_separator();
+
+    auto& scaling_mode_menu = view_menu.add_submenu("&Scaling Mode");
+
+    auto scaling_mode_group = make<GUI::ActionGroup>();
+    scaling_mode_group->set_exclusive(true);
+    scaling_mode_group->add_action(*nearest_neighbor_action);
+    scaling_mode_group->add_action(*bilinear_action);
+
+    scaling_mode_menu.add_action(nearest_neighbor_action);
+    scaling_mode_menu.add_action(bilinear_action);
+
     view_menu.add_separator();
     view_menu.add_action(hide_show_toolbar_action);