Mercurial > sdl-ios-xcode
changeset 2903:e426c4fc9cf7
Working Bresenham line drawing algorithm. We can optimize later, if needed.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sun, 21 Dec 2008 20:16:21 +0000 |
| parents | 83c3a4b0e421 |
| children | fa81cc1ef3d0 |
| files | src/video/SDL_draw.h |
| diffstat | 1 files changed, 47 insertions(+), 38 deletions(-) [+] |
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--- a/src/video/SDL_draw.h Sun Dec 21 17:55:02 2008 +0000 +++ b/src/video/SDL_draw.h Sun Dec 21 20:16:21 2008 +0000 @@ -283,49 +283,58 @@ #define ABS(_x) ((_x) < 0 ? -(_x) : (_x)) -#define SWAP(_x, _y) do { int tmp; tmp = _x; _x = _y; _y = tmp; } while (0) - -#define BRESENHAM(x0, y0, x1, y1, op) \ +#define BRESENHAM(x1, y1, x2, y2, op) \ { \ - int deltax, deltay, steep, error, xstep, ystep, x, y; \ + int i, deltax, deltay, numpixels; \ + int d, dinc1, dinc2; \ + int x, xinc1, xinc2; \ + int y, yinc1, yinc2; \ + \ + deltax = ABS(x2 - x1); \ + deltay = ABS(y2 - y1); \ \ - deltax = ABS(x1 - x0); \ - deltay = ABS(y1 - y0); \ - steep = (deltay > deltax); \ - if (steep) { \ - SWAP(x0, y0); \ - SWAP(x1, y1); \ - SWAP(deltax, deltay); \ - } \ - error = (x1 - x0) / 2; \ - y = y0; \ - if (x0 > x1) { \ - xstep = -1; \ + if (deltax >= deltay) { \ + numpixels = deltax + 1; \ + d = (2 * deltay) - deltax; \ + dinc1 = deltay * 2; \ + dinc2 = (deltay - deltax) * 2; \ + xinc1 = 1; \ + xinc2 = 1; \ + yinc1 = 0; \ + yinc2 = 1; \ } else { \ - xstep = 1; \ + numpixels = deltay + 1; \ + d = (2 * deltax) - deltay; \ + dinc1 = deltax * 2; \ + dinc2 = (deltax - deltay) * 2; \ + xinc1 = 0; \ + xinc2 = 1; \ + yinc1 = 1; \ + yinc2 = 1; \ } \ - if (y0 < y1) { \ - ystep = 1; \ - } else { \ - ystep = -1; \ + \ + if (x1 > x2) { \ + xinc1 = -xinc1; \ + xinc2 = -xinc2; \ + } \ + if (y1 > y2) { \ + yinc1 = -yinc1; \ + yinc2 = -yinc2; \ } \ - if (!steep) { \ - for (x = x0; x != x1; x += xstep) { \ - op(x, y); \ - error -= deltay; \ - if (error < 0) { \ - y += ystep; \ - error += deltax; \ - } \ - } \ - } else { \ - for (x = x0; x != x1; x += xstep) { \ - op(y, x); \ - error -= deltay; \ - if (error < 0) { \ - y += ystep; \ - error += deltax; \ - } \ + \ + x = x1; \ + y = y1; \ + \ + for (i = 1; i < numpixels; ++i) { \ + op(x, y); \ + if (d < 0) { \ + d += dinc1; \ + x += xinc1; \ + y += yinc1; \ + } else { \ + d += dinc2; \ + x += xinc2; \ + y += yinc2; \ } \ } \ }