Report

Report/uml/ellipse-arc-rasterization.puml

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+@startuml
+title Эллипс/дуга: алгоритм растризации
+
+start
+:Read rx, ry, thickness,\narc_percent, closed, filled;
+if (rx<=0 or ry<=0?) then (yes)
+  stop
+endif
+
+:Build local bbox corners with margin;
+:Transform corners to buffer\nand compute pixel scan bounds;
+:Create temporary transparent buffer;
+if (do_fill?) then (yes)
+  :startFill() collect border pixels;
+endif
+
+while (for each pixel in bbox)
+  :Map pixel center Buffer -> World -> Local;
+  :nx = x/rx, ny = y/ry,\nd = nx^2 + ny^2;
+  if (d in stroke ring?) then (yes)
+    if (arc_percent < 100?) then (yes)
+      :Compute angular position\nvia atan2 and normalized diff;
+      if (inside arc sector?) then (yes)
+        :plot stroke pixel;
+      endif
+    else (full ellipse)
+      :plot stroke pixel;
+    endif
+  endif
+endwhile
+
+if (closed and arc_percent<100?) then (yes)
+  :Draw two radial segments\n(center->start and center->end);
+endif
+
+if (do_fill?) then (yes)
+  :stopFill(fill_color);
+endif
+
+:Composite temp buffer to target\nonce with object opacity;
+stop
+
+@enduml