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+/****************************************************************************
+ * graphics/nxglib/nxglib_circletraps.c
+ *
+ * Copyright (C) 2011 Gregory Nutt. All rights reserved.
+ * Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ * used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * 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 OWNER 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <string.h>
+#include <errno.h>
+#include <fixedmath.h>
+
+#include <nuttx/nx/nxglib.h>
+
+/****************************************************************************
+ * Pre-Processor Definitions
+ ****************************************************************************/
+/* Trigonometry */
+
+#define SIN_0p0 0 /* sin(0) = 0 */
+#define COS_0p0 1 /* cos(0) = 1 */
+#define SIN_22p5 25080 /* sin(22.5) = 25080 / 65536 */
+#define COS_22p5 60547 /* cos(22.5) = 60547 / 65536 */
+#define SIN_45p0 46341 /* sin(45) = 46341 / 65536 */
+#define COS_45p0 SIN_45p0 /* cos(45) = sin(45) */
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: nxgl_circletraps
+ *
+ * Description:
+ * Given a description of a a circle, return 8 trapezoids that can be
+ * used to fill the circle by nx_fillcircle() and other interfaces.
+ *
+ * Input parameters:
+ * center - A pointer to the point that is the center of the circle
+ * radius - The radius of the circle in pixels.
+ * circle - A pointer the first entry in an array of 8 trapezoids where
+ * the circle description will be returned.
+ *
+ * Returned value:
+ * None
+ *
+ ****************************************************************************/
+
+void nxgl_circletraps(FAR const struct nxgl_point_s *center, nxgl_coord_t radius,
+ FAR struct nxgl_trapezoid_s *circle)
+{
+ nxgl_coord_t xoffs;
+ nxgl_coord_t yoffs;
+
+ circle[0].top.x1 = itob16(center->x);
+ circle[0].top.x2 = circle[0].top.x1;
+ circle[0].top.y = center->y - radius;
+
+ circle[7].bot.x1 = circle[0].top.x1;
+ circle[7].bot.x2 = circle[0].top.x1;
+ circle[7].bot.y = center->y + radius;
+
+ circle[3].bot.x1 = itob16(center->x - radius);
+ circle[3].bot.x2 = itob16(center->x + radius);
+ circle[3].bot.y = center->y;
+
+ circle[4].top.x1 = circle[3].bot.x1;
+ circle[4].top.x2 = circle[3].bot.x2;
+ circle[4].top.y = circle[3].bot.y;
+
+ /* Now 22.5, 67.5, 112.5, 157.5, 202.5, 247.5, 292.5, and 337.5 */
+
+ xoffs = b16toi(b16muli(COS_22p5, radius) + b16HALF);
+ yoffs = b16toi(b16muli(SIN_22p5, radius) + b16HALF);
+
+ circle[2].bot.x1 = itob16(center->x - xoffs);
+ circle[2].bot.x2 = itob16(center->x + xoffs);
+ circle[2].bot.y = center->y - yoffs;
+
+ circle[3].top.x1 = circle[2].bot.x1;
+ circle[3].top.x2 = circle[2].bot.x2;
+ circle[3].top.y = circle[2].bot.y;
+
+ circle[4].bot.x1 = circle[2].bot.x1;
+ circle[4].bot.x2 = circle[2].bot.x2;
+ circle[4].bot.y = center->y + yoffs;
+
+ circle[5].top.x1 = circle[4].bot.x1;
+ circle[5].top.x2 = circle[4].bot.x2;
+ circle[5].top.y = circle[4].bot.y;
+
+ circle[0].bot.x1 = itob16(center->x - yoffs);
+ circle[0].bot.x2 = itob16(center->x + yoffs);
+ circle[0].bot.y = center->y - xoffs;
+
+ circle[1].top.x1 = circle[0].bot.x1;
+ circle[1].top.x2 = circle[0].bot.x2;
+ circle[1].top.y = circle[0].bot.y;
+
+ circle[6].bot.x1 = circle[1].top.x1;
+ circle[6].bot.x2 = circle[1].top.x2;
+ circle[6].bot.y = center->y + xoffs;
+
+ circle[7].top.x1 = circle[6].bot.x1;
+ circle[7].top.x2 = circle[6].bot.x2;
+ circle[7].top.y = circle[6].bot.y;
+
+ /* Finally, 45.0, 135.0, 225.0, 315.0 */
+
+ xoffs = b16toi(b16muli(COS_45p0, radius) + b16HALF);
+
+ circle[1].bot.x1 = itob16(center->x - xoffs);
+ circle[1].bot.x2 = itob16(center->x + xoffs);
+ circle[1].bot.y = center->y - xoffs;
+
+ circle[2].top.x1 = circle[1].bot.x1;
+ circle[2].top.x2 = circle[1].bot.x2;
+ circle[2].top.y = circle[1].bot.y;
+
+ circle[5].bot.x1 = circle[1].bot.x1;
+ circle[5].bot.x2 = circle[1].bot.x2;
+ circle[5].bot.y = center->y + xoffs;
+
+ circle[6].top.x1 = circle[5].bot.x1;
+ circle[6].top.x2 = circle[5].bot.x2;
+ circle[6].top.y = circle[5].bot.y;
+}
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