LibGfx: Add Painter::get_pixel()

This is required to do some painting tricks in LibWeb, this has to be
added to the painter so it can apply the paint translation first.

Userland/Libraries/LibGfx/Painter.cpp

@@ -1205,37 +1205,37 @@ void Painter::draw_scaled_bitmap(IntRect const& a_dst_rect, Gfx::Bitmap const& s
     if (source.has_alpha_channel() || opacity != 1.0f) {
         switch (source.format()) {
         case BitmapFormat::BGRx8888:
-            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::BGRx8888>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::BGRx8888>, opacity, scaling_mode);
             break;
         case BitmapFormat::BGRA8888:
-            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::BGRA8888>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::BGRA8888>, opacity, scaling_mode);
             break;
         case BitmapFormat::Indexed8:
-            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::Indexed8>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::Indexed8>, opacity, scaling_mode);
             break;
         case BitmapFormat::Indexed4:
-            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::Indexed4>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::Indexed4>, opacity, scaling_mode);
             break;
         case BitmapFormat::Indexed2:
-            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::Indexed2>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::Indexed2>, opacity, scaling_mode);
             break;
         case BitmapFormat::Indexed1:
-            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::Indexed1>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::Indexed1>, opacity, scaling_mode);
             break;
         default:
-            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::Invalid>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<true>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::Invalid>, opacity, scaling_mode);
             break;
         }
     } else {
         switch (source.format()) {
         case BitmapFormat::BGRx8888:
-            do_draw_scaled_bitmap<false>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::BGRx8888>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<false>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::BGRx8888>, opacity, scaling_mode);
             break;
         case BitmapFormat::Indexed8:
-            do_draw_scaled_bitmap<false>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::Indexed8>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<false>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::Indexed8>, opacity, scaling_mode);
             break;
         default:
-            do_draw_scaled_bitmap<false>(*m_target, dst_rect, clipped_rect, source, src_rect, get_pixel<BitmapFormat::Invalid>, opacity, scaling_mode);
+            do_draw_scaled_bitmap<false>(*m_target, dst_rect, clipped_rect, source, src_rect, Gfx::get_pixel<BitmapFormat::Invalid>, opacity, scaling_mode);
             break;
         }
     }
@@ -1725,6 +1725,15 @@ void Painter::set_pixel(IntPoint const& p, Color color, bool blend)
     }
 }
 
+Optional<Color> Painter::get_pixel(IntPoint const& p)
+{
+    auto point = p;
+    point.translate_by(state().translation);
+    if (!clip_rect().contains(point / scale()))
+        return {};
+    return Color::from_argb(m_target->scanline(point.y())[point.x()]);
+}
+
 ALWAYS_INLINE void Painter::set_physical_pixel_with_draw_op(u32& pixel, Color const& color)
 {
     // This always sets a single physical pixel, independent of scale().

Userland/Libraries/LibGfx/Painter.h

@@ -59,6 +59,7 @@ public:
     void draw_ellipse_intersecting(IntRect const&, Color, int thickness = 1);
     void set_pixel(IntPoint const&, Color, bool blend = false);
     void set_pixel(int x, int y, Color color, bool blend = false) { set_pixel({ x, y }, color, blend); }
+    Optional<Color> get_pixel(IntPoint const&);
     void draw_line(IntPoint const&, IntPoint const&, Color, int thickness = 1, LineStyle style = LineStyle::Solid, Color alternate_color = Color::Transparent);
     void draw_triangle_wave(IntPoint const&, IntPoint const&, Color color, int amplitude, int thickness = 1);
     void draw_quadratic_bezier_curve(IntPoint const& control_point, IntPoint const&, IntPoint const&, Color, int thickness = 1, LineStyle style = LineStyle::Solid);