incubator-nuttx/libnx/nxglib/nxglib_circlepts.c

/****************************************************************************
 * graphics/nxglib/nxglib_circlepts.c
 *
 *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * 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) */

/* Named indices into the 16 circle points generated by nxgl_circlepts */

#define POINT_0p0      0
#define POINT_22p5     1
#define POINT_45p0     2
#define POINT_67p5     3
#define POINT_90p0     4
#define POINT_112p5    5
#define POINT_135p0    6
#define POINT_157p5    7
#define POINT_180p0    8
#define POINT_202p5    9
#define POINT_225p0    10
#define POINT_247p5    11
#define POINT_270p0    12
#define POINT_292p5    13
#define POINT_315p0    14
#define POINT_337p5    15
#define NCIRCLE_POINTS 16

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: nxgl_circlepts
 *
 * Description:
 *   Given a description of a circle, return a set of 16 points on the
 *   circumference of the circle.  These points may then be used by
 *   nx_drawcircle() or related APIs to draw a circle outline.
 *
 * 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 16 points where the
 *            circle points will be returned.
 *
 * Returned value:
 *   None
 *
 ****************************************************************************/

void nxgl_circlepts(FAR const struct nxgl_point_s *center, nxgl_coord_t radius,
                    FAR struct nxgl_point_s *circle)
{
  nxgl_coord_t xoffs;
  nxgl_coord_t yoffs;

  /* 0, 90, 180, and 270 degrees are the easiest */

  circle[POINT_0p0].x   = center->x + radius;
  circle[POINT_0p0].y   = center->y;
  circle[POINT_90p0].x  = center->x;
  circle[POINT_90p0].y  = center->y + radius;
  circle[POINT_180p0].x = center->x - radius;
  circle[POINT_180p0].y = center->y;
  circle[POINT_270p0].x = center->x;
  circle[POINT_270p0].y = center->y - radius;

  /* 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[POINT_22p5].x  = center->x + xoffs;
  circle[POINT_22p5].y  = center->y + yoffs;
  circle[POINT_157p5].x = center->x - xoffs;
  circle[POINT_157p5].y = center->y + yoffs;
  circle[POINT_202p5].x = center->x - xoffs;
  circle[POINT_202p5].y = center->y - yoffs;
  circle[POINT_337p5].x = center->x + xoffs;
  circle[POINT_337p5].y = center->y - yoffs;

  circle[POINT_67p5].x  = center->x + yoffs;
  circle[POINT_67p5].y  = center->y + xoffs;
  circle[POINT_112p5].x = center->x - yoffs;
  circle[POINT_112p5].y = center->y + xoffs;
  circle[POINT_247p5].x = center->x - yoffs;
  circle[POINT_247p5].y = center->y - xoffs;
  circle[POINT_292p5].x = center->x + yoffs;
  circle[POINT_292p5].y = center->y - xoffs;

  /* Finally, 45.0, 135.0, 225.0, 315.0 */

  xoffs = b16toi(b16muli(COS_45p0, radius) + b16HALF);

  circle[POINT_45p0].x  = center->x + xoffs;
  circle[POINT_45p0].y  = center->y + xoffs;
  circle[POINT_135p0].x = center->x - xoffs;
  circle[POINT_135p0].y = center->y + xoffs;
  circle[POINT_225p0].x = center->x - xoffs;
  circle[POINT_225p0].y = center->y - xoffs;
  circle[POINT_315p0].x = center->x + xoffs;
  circle[POINT_315p0].y = center->y - xoffs;
}