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comparison src/video/SDL_draw.h @ 2903:e426c4fc9cf7

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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 133601e3b255
children bd518fc76f28
comparison
equal deleted inserted replaced
2902:83c3a4b0e421 2903:e426c4fc9cf7
281 * Define line drawing macro 281 * Define line drawing macro
282 */ 282 */
283 283
284 #define ABS(_x) ((_x) < 0 ? -(_x) : (_x)) 284 #define ABS(_x) ((_x) < 0 ? -(_x) : (_x))
285 285
286 #define SWAP(_x, _y) do { int tmp; tmp = _x; _x = _y; _y = tmp; } while (0) 286 #define BRESENHAM(x1, y1, x2, y2, op) \
287
288 #define BRESENHAM(x0, y0, x1, y1, op) \
289 { \ 287 { \
290 int deltax, deltay, steep, error, xstep, ystep, x, y; \ 288 int i, deltax, deltay, numpixels; \
291 \ 289 int d, dinc1, dinc2; \
292 deltax = ABS(x1 - x0); \ 290 int x, xinc1, xinc2; \
293 deltay = ABS(y1 - y0); \ 291 int y, yinc1, yinc2; \
294 steep = (deltay > deltax); \ 292 \
295 if (steep) { \ 293 deltax = ABS(x2 - x1); \
296 SWAP(x0, y0); \ 294 deltay = ABS(y2 - y1); \
297 SWAP(x1, y1); \ 295 \
298 SWAP(deltax, deltay); \ 296 if (deltax >= deltay) { \
299 } \ 297 numpixels = deltax + 1; \
300 error = (x1 - x0) / 2; \ 298 d = (2 * deltay) - deltax; \
301 y = y0; \ 299 dinc1 = deltay * 2; \
302 if (x0 > x1) { \ 300 dinc2 = (deltay - deltax) * 2; \
303 xstep = -1; \ 301 xinc1 = 1; \
302 xinc2 = 1; \
303 yinc1 = 0; \
304 yinc2 = 1; \
304 } else { \ 305 } else { \
305 xstep = 1; \ 306 numpixels = deltay + 1; \
306 } \ 307 d = (2 * deltax) - deltay; \
307 if (y0 < y1) { \ 308 dinc1 = deltax * 2; \
308 ystep = 1; \ 309 dinc2 = (deltax - deltay) * 2; \
309 } else { \ 310 xinc1 = 0; \
310 ystep = -1; \ 311 xinc2 = 1; \
311 } \ 312 yinc1 = 1; \
312 if (!steep) { \ 313 yinc2 = 1; \
313 for (x = x0; x != x1; x += xstep) { \ 314 } \
314 op(x, y); \ 315 \
315 error -= deltay; \ 316 if (x1 > x2) { \
316 if (error < 0) { \ 317 xinc1 = -xinc1; \
317 y += ystep; \ 318 xinc2 = -xinc2; \
318 error += deltax; \ 319 } \
319 } \ 320 if (y1 > y2) { \
320 } \ 321 yinc1 = -yinc1; \
321 } else { \ 322 yinc2 = -yinc2; \
322 for (x = x0; x != x1; x += xstep) { \ 323 } \
323 op(y, x); \ 324 \
324 error -= deltay; \ 325 x = x1; \
325 if (error < 0) { \ 326 y = y1; \
326 y += ystep; \ 327 \
327 error += deltax; \ 328 for (i = 1; i < numpixels; ++i) { \
328 } \ 329 op(x, y); \
330 if (d < 0) { \
331 d += dinc1; \
332 x += xinc1; \
333 y += yinc1; \
334 } else { \
335 d += dinc2; \
336 x += xinc2; \
337 y += yinc2; \
329 } \ 338 } \
330 } \ 339 } \
331 } 340 }
332 #define DRAWLINE(x0, y0, x1, y1, op) BRESENHAM(x0, y0, x1, y1, op) 341 #define DRAWLINE(x0, y0, x1, y1, op) BRESENHAM(x0, y0, x1, y1, op)
333 342