PixelPaint: Let PickerTool optionally sample all layers

Previously, only the color from the selected layer would be picked.
Now, we allow the user to select if they want to sample the color
from all layers.

4 files changed, 58 insertions, 7 deletions

diff --git a/Userland/Applications/PixelPaint/Image.cpp b/Userland/Applications/PixelPaint/Image.cpp
index 191dd512af..4c9d88db41 100644
--- a/Userland/Applications/PixelPaint/Image.cpp
+++ b/Userland/Applications/PixelPaint/Image.cpp
@@ -532,4 +532,19 @@ void Image::crop(Gfx::IntRect const& cropped_rect)
     did_change_rect(cropped_rect);
 }
 
+Color Image::color_at(Gfx::IntPoint const& point) const
+{
+    Color color;
+    for (auto& layer : m_layers) {
+        if (!layer.is_visible() || !layer.rect().contains(point))
+            continue;
+
+        auto layer_color = layer.bitmap().get_pixel(point);
+        float layer_opacity = layer.opacity_percent() / 100.0f;
+        layer_color.set_alpha((u8)(layer_color.alpha() * layer_opacity));
+        color = color.blend(layer_color);
+    }
+    return color;
+}
+
 }
diff --git a/Userland/Applications/PixelPaint/Image.h b/Userland/Applications/PixelPaint/Image.h
index daa508075b..116954ff38 100644
--- a/Userland/Applications/PixelPaint/Image.h
+++ b/Userland/Applications/PixelPaint/Image.h
@@ -103,6 +103,8 @@ public:
     void rotate(Gfx::RotationDirection direction);
     void crop(Gfx::IntRect const& rect);
 
+    Color color_at(Gfx::IntPoint const& point) const;
+
 private:
     explicit Image(Gfx::IntSize const&);
 
diff --git a/Userland/Applications/PixelPaint/PickerTool.cpp b/Userland/Applications/PixelPaint/PickerTool.cpp
index 0fd91f9264..e46a52a12e 100644
--- a/Userland/Applications/PixelPaint/PickerTool.cpp
+++ b/Userland/Applications/PixelPaint/PickerTool.cpp
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Mustafa Quraish <mustafa@cs.toronto.edu>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -7,6 +8,8 @@
 #include "PickerTool.h"
 #include "ImageEditor.h"
 #include "Layer.h"
+#include <LibGUI/BoxLayout.h>
+#include <LibGUI/CheckBox.h>
 
 namespace PixelPaint {
 
@@ -20,17 +23,41 @@ PickerTool::~PickerTool()
 
 void PickerTool::on_mousedown(Layer* layer, MouseEvent& event)
 {
-    if (!layer)
-        return;
+    auto& position = event.layer_event().position();
+
+    Color color;
+    if (m_sample_all_layers) {
+        color = m_editor->image().color_at(position);
+    } else {
+        if (!layer || !layer->rect().contains(position))
+            return;
+        color = layer->bitmap().get_pixel(position);
+    }
 
-    auto& layer_event = event.layer_event();
-    if (!layer->rect().contains(layer_event.position()))
+    // We picked a transparent pixel, do nothing.
+    if (!color.alpha())
         return;
-    auto color = layer->bitmap().get_pixel(layer_event.position());
-    if (layer_event.button() == GUI::MouseButton::Left)
+
+    if (event.layer_event().button() == GUI::MouseButton::Left)
         m_editor->set_primary_color(color);
-    else if (layer_event.button() == GUI::MouseButton::Right)
+    else if (event.layer_event().button() == GUI::MouseButton::Right)
         m_editor->set_secondary_color(color);
 }
 
+GUI::Widget* PickerTool::get_properties_widget()
+{
+    if (!m_properties_widget) {
+        m_properties_widget = GUI::Widget::construct();
+        m_properties_widget->set_layout<GUI::VerticalBoxLayout>();
+
+        auto& sample_checkbox = m_properties_widget->add<GUI::CheckBox>("Sample all layers");
+        sample_checkbox.set_checked(m_sample_all_layers);
+        sample_checkbox.on_checked = [&](bool value) {
+            m_sample_all_layers = value;
+        };
+    }
+
+    return m_properties_widget.ptr();
+}
+
 }
diff --git a/Userland/Applications/PixelPaint/PickerTool.h b/Userland/Applications/PixelPaint/PickerTool.h
index 0989795d1d..6a00a34d40 100644
--- a/Userland/Applications/PixelPaint/PickerTool.h
+++ b/Userland/Applications/PixelPaint/PickerTool.h
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Mustafa Quraish <mustafa@cs.toronto.edu>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -16,7 +17,13 @@ public:
     virtual ~PickerTool() override;
 
     virtual void on_mousedown(Layer*, MouseEvent&) override;
+
+    virtual GUI::Widget* get_properties_widget() override;
     virtual Gfx::StandardCursor cursor() override { return Gfx::StandardCursor::Eyedropper; }
+
+private:
+    RefPtr<GUI::Widget> m_properties_widget;
+    bool m_sample_all_layers { false };
 };
 
 }