git.sur5r.net Git - cc65/blob - libsrc/tgi/tgi_ellipse.c

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                               tgi_ellipse.c                               */
   4 /*                                                                           */
   5 /*                            Draw a full ellipse                            */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2002-2009, Ullrich von Bassewitz                                      */
  10 /*                Roemerstrasse 52                                           */
  11 /*                D-70794 Filderstadt                                        */
  12 /* EMail:         uz@cc65.org                                                */
  13 /*                                                                           */
  14 /*                                                                           */
  15 /* This software is provided 'as-is', without any expressed or implied       */
  16 /* warranty.  In no event will the authors be held liable for any damages    */
  17 /* arising from the use of this software.                                    */
  18 /*                                                                           */
  19 /* Permission is granted to anyone to use this software for any purpose,     */
  20 /* including commercial applications, and to alter it and redistribute it    */
  21 /* freely, subject to the following restrictions:                            */
  22 /*                                                                           */
  23 /* 1. The origin of this software must not be misrepresented; you must not   */
  24 /*    claim that you wrote the original software. If you use this software   */
  25 /*    in a product, an acknowledgment in the product documentation would be  */
  26 /*    appreciated but is not required.                                       */
  27 /* 2. Altered source versions must be plainly marked as such, and must not   */
  28 /*    be misrepresented as being the original software.                      */
  29 /* 3. This notice may not be removed or altered from any source              */
  30 /*    distribution.                                                          */
  31 /*                                                                           */
  32 /*****************************************************************************/
  33
  34
  35
  36 #include <tgi.h>
  37 #include <cc65.h>
  38
  39
  40
  41 /*****************************************************************************/
  42 /*                                   Code                                    */
  43 /*****************************************************************************/
  44
  45
  46
  47 static int RoundMul (int rhs, int lhs)
  48 {
  49     long res = cc65_imul16x16r32 (rhs, lhs);
  50     if ((unsigned char)res & 0x80) {
  51         return (int)(res >> 8) + 1;
  52     } else {
  53         return (int)(res >> 8);
  54     }
  55 }
  56
  57
  58
  59 void __fastcall__ tgi_ellipse (int x, int y, unsigned char rx, unsigned char ry)
  60 /* Draw a full ellipse with center at x/y and radii rx/ry using the current
  61  * drawing color.
  62  */
  63 {
  64     int x1, y1, x2, y2;
  65     unsigned angle;
  66     unsigned char inc;
  67     unsigned size = rx + ry;
  68
  69     if (size >= 128) {
  70         inc = 12;
  71     } else if (size >= 32) {
  72         inc = 15;
  73     } else if (size >= 12) {
  74         inc = 20;
  75     } else {
  76         inc = 45;
  77     }
  78
  79     x1 = x + rx;
  80     y1 = y;
  81     angle = 0;
  82     for (angle = 0; angle <= 360; angle += inc) {
  83         x2 = x + RoundMul (rx, cc65_cos (angle));
  84         y2 = y + RoundMul (ry, cc65_sin (angle));
  85         tgi_line (x1, y1, x2, y2);
  86         x1 = x2;
  87         y1 = y2;
  88     }
  89 }
  90
  91
  92