PixelPaint: Basic brush tool

This patch adds a very basic implementation of the classic brush
tool. It features a wide brush with a falloff around the edges.

Applications/PixelPaint/BrushTool.cpp

@@ -0,0 +1,114 @@
+/*
+ * Copyright (c) 2020, Ben Jilks <benjyjilks@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "BrushTool.h"
+#include "ImageEditor.h"
+#include "Layer.h"
+#include <LibGUI/Action.h>
+#include <LibGUI/Painter.h>
+#include <LibGfx/Color.h>
+#include <LibGfx/Rect.h>
+
+namespace PixelPaint {
+
+BrushTool::BrushTool()
+{
+}
+
+BrushTool::~BrushTool()
+{
+}
+
+void BrushTool::on_mousedown(Layer&, GUI::MouseEvent& event, GUI::MouseEvent&)
+{
+    if (event.button() != GUI::MouseButton::Left && event.button() != GUI::MouseButton::Right)
+        return;
+
+    m_last_position = event.position();
+}
+
+void BrushTool::on_mousemove(Layer& layer, GUI::MouseEvent& event, GUI::MouseEvent&)
+{
+    if (!(event.buttons() & GUI::MouseButton::Left || event.buttons() & GUI::MouseButton::Right))
+        return;
+
+    draw_line(layer.bitmap(), m_editor->color_for(event), m_last_position, event.position());
+    layer.did_modify_bitmap(*m_editor->image());
+    m_last_position = event.position();
+}
+
+void BrushTool::draw_point(Gfx::Bitmap& bitmap, const Gfx::Color& color, const Gfx::IntPoint& point)
+{
+    for (int y = point.y() - m_size; y < point.y() + m_size; y++) {
+        for (int x = point.x() - m_size; x < point.x() + m_size; x++) {
+            auto distance = point.distance_from({ x, y });
+            if (x < 0 || x >= bitmap.width() || y < 0 || y >= bitmap.height())
+                continue;
+            if (distance >= m_size)
+                continue;
+
+            auto falloff = (1.0 - (distance / (float)m_size)) * 0.2;
+            auto pixel_color = color;
+            pixel_color.set_alpha(falloff * 255);
+            bitmap.set_pixel(x, y, bitmap.get_pixel(x, y).blend(pixel_color));
+        }
+    }
+}
+
+void BrushTool::draw_line(Gfx::Bitmap& bitmap, const Gfx::Color& color, const Gfx::IntPoint& start, const Gfx::IntPoint& end)
+{
+    int length_x = end.x() - start.x();
+    int length_y = end.y() - start.y();
+    float y_step = length_y == 0 ? 0 : (float)(length_y) / (float)(length_x);
+    if (y_step > abs(length_y))
+        y_step = abs(length_y);
+    if (y_step < -abs(length_y))
+        y_step = -abs(length_y);
+    if (y_step == 0 && start.x() == end.x())
+        return;
+
+    int start_x = start.x();
+    int end_x = end.x();
+    int start_y = start.y();
+    int end_y = end.y();
+    if (start_x > end_x) {
+        swap(start_x, end_x);
+        swap(start_y, end_y);
+    }
+
+    float y = start_y;
+    for (int x = start_x; x <= end_x; x++) {
+        int start_step_y = y;
+        int end_step_y = y + y_step;
+        if (start_step_y > end_step_y)
+            swap(start_step_y, end_step_y);
+        for (int i = start_step_y; i <= end_step_y; i++)
+            draw_point(bitmap, color, { x, i });
+        y += y_step;
+    }
+}
+
+}

Applications/PixelPaint/BrushTool.h

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2020, Ben Jilks <benjyjilks@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "Tool.h"
+
+namespace PixelPaint {
+
+class BrushTool final : public Tool {
+public:
+    BrushTool();
+    virtual ~BrushTool() override;
+
+    virtual void on_mousedown(Layer&, GUI::MouseEvent& layer_event, GUI::MouseEvent& image_event) override;
+    virtual void on_mousemove(Layer&, GUI::MouseEvent& layer_event, GUI::MouseEvent& image_event) override;
+
+private:
+    int m_size { 10 };
+    Gfx::IntPoint m_last_position;
+
+    virtual const char* class_name() const override { return "BrushTool"; }
+    void draw_line(Gfx::Bitmap& bitmap, const Gfx::Color& color, const Gfx::IntPoint& start, const Gfx::IntPoint& end);
+    void draw_point(Gfx::Bitmap& bitmap, const Gfx::Color& color, const Gfx::IntPoint& point);
+};
+
+}

Applications/PixelPaint/CMakeLists.txt

@@ -1,4 +1,5 @@
 set(SOURCES
+    BrushTool.cpp
     BucketTool.cpp
     CreateNewLayerDialog.cpp
     EllipseTool.cpp

Applications/PixelPaint/ToolboxWidget.cpp

@@ -25,6 +25,7 @@
  */
 
 #include "ToolboxWidget.h"
+#include "BrushTool.h"
 #include "BucketTool.h"
 #include "EllipseTool.h"
 #include "EraseTool.h"
@@ -127,6 +128,7 @@ void ToolboxWidget::setup_tools()
 
     add_tool("Move", "move", { 0, Key_M }, make<MoveTool>());
     add_tool("Pen", "pen", { 0, Key_N }, make<PenTool>());
+    add_tool("Brush", "brush", { 0, Key_P }, make<BrushTool>());
     add_tool("Bucket Fill", "bucket", { Mod_Shift, Key_B }, make<BucketTool>());
     add_tool("Spray", "spray", { Mod_Shift, Key_S }, make<SprayTool>());
     add_tool("Color Picker", "picker", { 0, Key_O }, make<PickerTool>());