From bfba3999b5cee49bd9a556f51170193849228a46 Mon Sep 17 00:00:00 2001
From: Edouard Dupin <yui.heero@gmail.com>
Date: Thu, 6 Sep 2012 02:50:38 +0200
Subject: [PATCH] add distance field calculation for the Image draw absraction
 system

---
 draw/Image.cpp | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++
 draw/Image.h   | 79 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 174 insertions(+)

diff --git a/draw/Image.cpp b/draw/Image.cpp
index 3d40c2d..14b99d9 100644
--- a/draw/Image.cpp
+++ b/draw/Image.cpp
@@ -259,3 +259,98 @@ void draw::Image::Disc(Vector2D<float> pos, float radius, float angleStart, floa
 	
 }
 
+void GenerateSDF( Grid &g )
+{
+	// Pass 0
+	Vector2D<int32_t> tmpPos;
+	for (tmpPos.y=1 ; tmpPos.y<g.m_size.y-1 ; tmpPos.y++) {
+		for (tmpPos.x=1 ; tmpPos.x<g.m_size.x-1 ; tmpPos.x++) {
+			Vector2D<int32_t> p = g.Get(tmpPos);
+			g.Compare(p, tmpPos, -1,  0 );
+			g.Compare(p, tmpPos,  0, -1 );
+			g.Compare(p, tmpPos, -1, -1 );
+			g.Compare(p, tmpPos,  1, -1 );
+			g.Set(tmpPos, p);
+		}
+		for (tmpPos.x=g.m_size.x-2 ; tmpPos.x>0 ; tmpPos.x--) {
+			Vector2D<int32_t> p = g.Get(tmpPos);
+			g.Compare(p, tmpPos, 1, 0 );
+			g.Set(tmpPos, p );
+		}
+	}
+	// Pass 1
+	for (tmpPos.y=g.m_size.y-2 ; tmpPos.y>0 ; tmpPos.y--) {
+		for (tmpPos.x=g.m_size.x-2 ; tmpPos.x>0 ; tmpPos.x--) {
+			Vector2D<int32_t> p = g.Get(tmpPos);
+			g.Compare(p, tmpPos,  1,  0 );
+			g.Compare(p, tmpPos,  0,  1 );
+			g.Compare(p, tmpPos, -1,  1 );
+			g.Compare(p, tmpPos,  1,  1 );
+			g.Set(tmpPos, p);
+		}
+		for (tmpPos.x=1 ; tmpPos.x<g.m_size.x-1 ; tmpPos.x++) {
+			Vector2D<int32_t> p = g.Get(tmpPos);
+			g.Compare(p, tmpPos, -1,  0 );
+			g.Set(tmpPos, p);
+		}
+	}
+}
+
+// see : http://www.codersnotes.com/notes/signed-distance-fields
+
+void draw::Image::DistanceField(void)
+{
+	DistanceField(Vector2D<int32_t>(0,0), m_size);
+}
+void draw::Image::DistanceField(Vector2D<int32_t> pos, Vector2D<int32_t> size)
+{
+	Grid grid1(size);
+	Grid grid2(size);
+	grid1.SetOutsideVal(50);
+	grid2.SetOutsideVal(50);
+	
+	Vector2D<int32_t> tmpPos;
+	for(tmpPos.y=0 ; tmpPos.y<size.x ; tmpPos.y++ ) {
+		for(tmpPos.x=0 ; tmpPos.x<size.y ; tmpPos.x++ ) {
+			draw::Color tmpColor = Get(pos+tmpPos);
+			// Points inside get marked with a x/y of zero.
+			// Points outside get marked with an infinitely large distance.
+			if (tmpColor.a<=0x7F) {
+				grid1.SetInide(tmpPos);
+				grid2.SetOutside(tmpPos);
+			} else {
+				grid2.SetInide(tmpPos);
+				grid1.SetOutside(tmpPos);
+			}
+		}
+	}
+	
+	// Generate the SDF:
+	GenerateSDF( grid1 );
+	GenerateSDF( grid2 );
+	
+	for(tmpPos.y=0 ; tmpPos.y<size.x ; tmpPos.y++ ) {
+		for(tmpPos.x=0 ; tmpPos.x<size.y ; tmpPos.x++ ) {
+			Vector2D<int32_t> elem1 = grid1.Get(tmpPos);
+			Vector2D<int32_t> elem2 = grid2.Get(tmpPos);
+			// Calculate the actual distance from the x/y
+			float dist1 = sqrt( (double)elem1.QuadDist() );
+			float dist2 = sqrt( (double)elem2.QuadDist() );
+			float dist = dist1 - dist2;
+			/*
+			if (tmpPos.y < 32) {
+				if (tmpPos.x < 32) {
+					DRAW_DEBUG( "generate Distance : " << dist1 << "," << dist2 << " ==> " << (dist*3 + 128));
+				} else if (tmpPos.x == 32) {
+					DRAW_DEBUG( " ---" );
+				}
+			}
+			*/
+			draw::Color tmpColor = Get(pos+tmpPos);
+			// Clamp and scale it, just for display purposes.
+			tmpColor.a = etk_avg(0, (dist*3 + 128), 255);
+			Set(pos+tmpPos, tmpColor);
+		}
+	}
+}
+
diff --git a/draw/Image.h b/draw/Image.h
index a5768d8..9cf0276 100644
--- a/draw/Image.h
+++ b/draw/Image.h
@@ -42,6 +42,79 @@
 #include <agg/agg_color_rgba.h>
 #include <agg/agg_pixfmt_rgba.h>
 
+
+
+class Grid
+{
+	public:
+		Vector2D<int32_t>               m_size;
+		etk::Vector<Vector2D<int32_t> > m_data;
+		int32_t                         m_outsideVal;
+		Grid(Vector2D<int32_t> size)
+		{
+			m_size = size;
+			m_outsideVal = 20;
+			// basic element :
+			Vector2D<int32_t> tmpPoint(0,0);
+			// preallocate data with a basic bg elements :
+			m_data.ReSize(m_size.x*m_size.y, tmpPoint);
+		};
+		~Grid(void) { };
+		void SetOutsideVal(int32_t newVal)
+		{
+			m_outsideVal = newVal;
+		}
+		void SetInide(Vector2D<int32_t> pos)
+		{
+			if(    pos.x>=0 && pos.x<m_size.x
+			    && pos.y>=0 && pos.y<m_size.y) {
+				m_data[pos.x+pos.y*m_size.x].x=0;
+				m_data[pos.x+pos.y*m_size.x].y=0;
+			}
+		};
+		void SetOutside(Vector2D<int32_t> pos)
+		{
+			if(    pos.x>=0 && pos.x<m_size.x
+			    && pos.y>=0 && pos.y<m_size.y) {
+				m_data[pos.x+pos.y*m_size.x].x=m_outsideVal;
+				m_data[pos.x+pos.y*m_size.x].y=m_outsideVal;
+			}
+		};
+		
+		Vector2D<int32_t> Get(Vector2D<int32_t> pos)
+		{
+			;
+			if(    pos.x>0 && pos.x<m_size.x
+			    && pos.y>0 && pos.y<m_size.y) {
+				return m_data[pos.x+pos.y*m_size.x];
+			}
+			return Vector2D<int32_t>(0,0);
+		};
+		
+		void Set(Vector2D<int32_t> pos, Vector2D<int32_t> val)
+		{
+			if(    pos.x>0 && pos.x<m_size.x
+			    && pos.y>0 && pos.y<m_size.y) {
+				m_data[pos.x+pos.y*m_size.x] = val;
+			}
+		};
+		
+		void Compare(Vector2D<int32_t> &p, Vector2D<int32_t> pos, int32_t offsetx, int32_t offsety )
+		{
+			pos.x += offsetx;
+			pos.y += offsety;
+			Vector2D<int32_t> other = Get(pos);
+			other.x += offsetx;
+			other.y += offsety;
+			
+			if (other.QuadDist() < p.QuadDist()) {
+				p = other;
+			}
+		};
+};
+
+
+
 namespace draw
 {
 	
@@ -162,6 +235,12 @@ namespace draw
 			void Rectangle(Vector2D<float> pos, Vector2D<float> size);
 			void Circle(Vector2D<float> pos, float radius, float angleStart=0, float angleStop=2*M_PI);
 			void Disc(Vector2D<float> pos, float radius, float angleStart=0, float angleStop=2*M_PI);
+			// generate the distant field from the alpha value of the Image
+			void DistanceField(void);
+			void DistanceField(Vector2D<int32_t> pos, Vector2D<int32_t> size);
+		private:
+			
+			
 	};
 	
 };