pixel based brush size, Photoshop slider curve, improve abr import

src/node_panel_brush.h

@@ -104,6 +104,7 @@ class NodePanelBrushPreset : public Node
         int m_stencil_thumb_path_len = 0;
 
         glm::vec4 m_tip_color{ 0, 0, 0, 1 };
+        float m_tip_width = 1.f;
         float m_tip_size = 0;
         float m_tip_spacing = 0;
         float m_tip_flow = 0;