Merge pull request #24 from srandoux/master

Added DrawCircle and DrawLine contributed by @srandoux
hzeller · Apr 7, 2015 · 44a1c0e · 44a1c0e
2 parents 4adfb0e + 6474b43
commit 44a1c0e
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Showing 2 changed files with 58 additions and 2 deletions.
diff --git a/include/graphics.h b/include/graphics.h
@@ -65,8 +65,10 @@ class Font {
 // Returns how far we advance on the screen.
 int DrawText(Canvas *c, const Font &font, int x, int y, const Color &color,
              const char *utf8_text);
-
-// lines, circles and stuff.
+// Draw a circle centered at "x0", "y0", with a radius of "radius" and with "color"
+void DrawCircle(Canvas *c, int32_t x0, int32_t y0, int32_t radius, const Color &color);
+// Draw a line from "x0", "y0" to "x1", "y1" and with "color"
+void DrawLine(Canvas *c, int32_t x0, int32_t y0, int32_t x1, int32_t y1, const Color &color);
 
 }  // namespace rgb_matrix
 

diff --git a/lib/graphics.cc b/lib/graphics.cc
@@ -15,6 +15,8 @@
 
 #include "graphics.h"
 #include "utf8-internal.h"
+#include <stdlib.h>
+#include <functional>
 
 namespace rgb_matrix {
 int DrawText(Canvas *c, const Font &font,
@@ -27,4 +29,56 @@ int DrawText(Canvas *c, const Font &font,
   }
   return x - start_x;
 }
+
+
+void DrawCircle(Canvas *c, int32_t x0, int32_t y0, int32_t radius, const Color &color){
+int32_t x = radius, y = 0;
+int32_t radiusError = 1 - x;
+
+  while (y <= x){
+    c->SetPixel(x + x0, y + y0, color.r, color.g, color.b);
+    c->SetPixel(y + x0, x + y0, color.r, color.g, color.b);
+    c->SetPixel(-x + x0, y + y0, color.r, color.g, color.b);
+    c->SetPixel(-y + x0, x + y0, color.r, color.g, color.b);
+    c->SetPixel(-x + x0, -y + y0, color.r, color.g, color.b);
+    c->SetPixel(-y + x0, -x + y0, color.r, color.g, color.b);
+    c->SetPixel(x + x0, -y + y0, color.r, color.g, color.b);
+    c->SetPixel(y + x0, -x + y0, color.r, color.g, color.b);
+    y++;
+    if (radiusError<0){
+      radiusError += 2 * y + 1;
+    } else {
+      x--;
+      radiusError+= 2 * (y - x + 1);
+    }
+  }
+}
+
+void DrawLine(Canvas *c, int32_t x0, int32_t y0, int32_t x1, int32_t y1, const Color &color){
+  int32_t dy = y1 - y0, dx = x1 - x0, gradient, x, y, shift = 0x10;
+
+  if (abs(dx) > abs(dy)) {
+    // x variation is bigger than y variation
+    if (x1 < x0) {
+      std::swap(x0, x1);
+      std::swap(y0, y1);
+    }
+    gradient = (dy << shift) / dx ;
+
+    for (x = x0 , y = 0x8000 + (y0 << shift); x <= x1; ++x, y += gradient) {
+      c->SetPixel(x, y >> shift, color.r, color.g, color.b);
+    }
+  } else {
+    // y variation is bigger than x variation
+    if (y1 < y0) {
+      std::swap(x0, x1);
+      std::swap(y0, y1);
+    }
+    gradient = (dx << shift) / dy;
+    for (y = y0 , x = 0x8000 + (x0 << shift); y <= y1; ++y, x += gradient) {
+      c->SetPixel(x >> shift, y, color.r, color.g, color.b);
+    }
+  }
 }
+
+}//namespace