glib_circle.c

Go to the documentation of this file.

 /*************************************************************************/
/* Standard C header files */
#include <stdint.h>
/* EM types */
#include "em_types.h"

/* GLIB header files */
#include "glib.h"

/* Local function prototypes */
static EMSTATUS GLIB_drawPartialCirclePoints(GLIB_Context_t *pContext,
                                             int32_t xCenter, int32_t yCenter,
                                             int32_t x, int32_t y, uint8_t bitMask);

/**************************************************************************/
EMSTATUS GLIB_drawCircle(GLIB_Context_t *pContext, int32_t xCenter,
                         int32_t yCenter, uint32_t radius)
{
  return GLIB_drawPartialCircle(pContext, xCenter, yCenter, radius, 0xFF);
}

/**************************************************************************/
EMSTATUS GLIB_drawPartialCircle(GLIB_Context_t *pContext, int32_t xCenter,
                                int32_t yCenter, uint32_t radius, uint8_t bitMask)
{
  EMSTATUS status;
  int32_t x = 0;
  int32_t y = radius;
  int32_t d = 1 - radius;
  uint32_t drawnElements = 0;

  /* Check arguments */
  if (pContext == NULL) return GLIB_ERROR_INVALID_ARGUMENT;

  /* Draw initial circle points */
  status = GLIB_drawPartialCirclePoints(pContext, xCenter, yCenter, x, y, bitMask);
  if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
  if (status == GLIB_OK) drawnElements++;

  /* Loops through all points from 0 to 45 degrees (1 octant) of the circle
   * (0 is defined straight upward) */
  while (x < y) {
    if (d < 0) {
      d += 2 * x + 1;
    } else {
      y--;
      d += 2 * (x - y) + 1;
    }

    /* Draws the circle points using 8-way symmetry */
    status = GLIB_drawPartialCirclePoints(pContext, xCenter, yCenter, x, y, bitMask);
    x++;
    if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
    if (status == GLIB_OK) drawnElements++;
  }
  return ((drawnElements == 0) ? GLIB_ERROR_NOTHING_TO_DRAW : GLIB_OK);
}

/**************************************************************************/
EMSTATUS GLIB_drawCircleFilled(GLIB_Context_t *pContext, int32_t xCenter,
                               int32_t yCenter, uint32_t radius)
{
  EMSTATUS status;
  int32_t x = 0;
  int32_t y = radius;
  int32_t d = 1 - radius;
  uint32_t drawnElements = 0;

  /* Check arguments */
  if (pContext == NULL) return GLIB_ERROR_INVALID_ARGUMENT;

  /* Draws the initial circle fill line */
  status = GLIB_drawLineH(pContext, xCenter - y, yCenter, xCenter + y);
  if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
  if (status == GLIB_OK) drawnElements++;

  /* Loops through all points from 0 to 45 degrees of the circle
   * (0 is defined straight upward) */
  while (x < y) {
    if (d < 0) {
      d += 2 * x + 1;
    } else {
      y--;
      d += 2 * (x - y) + 1;
    }

    /* Draws horizontal fill lines using 4 way symmetry */
    status = GLIB_drawLineH(pContext, xCenter - x, yCenter + y, xCenter + x);
    if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
    if (status == GLIB_OK) drawnElements++;

    status = GLIB_drawLineH(pContext, xCenter - y, yCenter + x, xCenter + y);
    if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
    if (status == GLIB_OK) drawnElements++;

    status = GLIB_drawLineH(pContext, xCenter - x, yCenter - y, xCenter + x);
    if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
    if (status == GLIB_OK) drawnElements++;

    status = GLIB_drawLineH(pContext, xCenter - y, yCenter - x, xCenter + y);
    if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
    if (status == GLIB_OK) drawnElements++;

    x++;
  }
  return ((drawnElements == 0) ? GLIB_ERROR_NOTHING_TO_DRAW : GLIB_OK);
}

/**************************************************************************/
static EMSTATUS GLIB_drawPartialCirclePoints(GLIB_Context_t *pContext,
                                             int32_t xCenter, int32_t yCenter,
                                             int32_t x, int32_t y, uint8_t bitMask)
{
  EMSTATUS status;
  uint32_t drawnElements = 0;
  uint32_t i;

  /* Draw the circle points using 8-way symmetry */
  int32_t  xOffsets[] = {y, x, -x, -y, -y, -x, x, y};
  int32_t  yOffsets[] = {-x, -y, -y, -x, x, y, y, x};

  i = 0;
  while (bitMask)
  {
    /* Pixel in i+1. octant */
    if (bitMask & 0x1)
    {
      status = GLIB_drawPixel(pContext, xCenter + xOffsets[i], yCenter + yOffsets[i]);
      if (status > GLIB_ERROR_NOTHING_TO_DRAW) return status;
      if (status == GLIB_OK) drawnElements++;
    }
    bitMask >>= 1;
    i++;
  }
  return ((drawnElements == 0) ? GLIB_ERROR_NOTHING_TO_DRAW : GLIB_OK);
}