wrlib/draw.c

   1 /* draw.c - pixel plotting, line drawing
   2  *
   3  *  Raster graphics library
   4  *
   5  *  Copyright (c) 1998 Dan Pascu
   6  *  Copyright (c) 2000 Alfredo K. Kojima
   7  *
   8  *  This library is free software; you can redistribute it and/or
   9  *  modify it under the terms of the GNU Library General Public
  10  *  License as published by the Free Software Foundation; either
  11  *  version 2 of the License, or (at your option) any later version.
  12  *
  13  *  This library is distributed in the hope that it will be useful,
  14  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  *  Library General Public License for more details.
  17  *
  18  *  You should have received a copy of the GNU Library General Public
  19  *  License along with this library; if not, write to the Free
  20  *  Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  */
  22
  23 #include <config.h>
  24
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <assert.h>
  28
  29 #include "wraster.h"
  30
  31
  32 #define MIN(a,b)        ((a) < (b) ? (a) : (b))
  33 #define MAX(a,b)        ((a) > (b) ? (a) : (b))
  34
  35
  36
  37 /*
  38  * Returns the color of the pixel at coordinates (x, y) in "color".
  39  */
  40 Bool
  41 RGetPixel(RImage *image, int x, int y, RColor *color)
  42 {
  43     int ofs;
  44
  45     assert(image!=NULL);
  46     if (x < 0 || x >= image->width
  47         || y < 0 || y >= image->height)
  48         return False;
  49
  50     if (image->format == RRGBAFormat) {
  51         ofs = (y*image->width + x) * 4;
  52         color->red = image->data[ofs];
  53         color->green = image->data[ofs++];
  54         color->blue = image->data[ofs++];
  55         color->alpha = image->data[ofs];
  56     } else {
  57         ofs = (y*image->width + x) * 3;
  58         color->red = image->data[ofs++];
  59         color->green = image->data[ofs++];
  60         color->blue = image->data[ofs++];
  61         /* If the image does not have alpha channel, we consider alpha 255 */
  62         color->alpha = 255;
  63     }
  64
  65     return True;
  66 }
  67
  68
  69 void
  70 RPutPixel(RImage *image, int x, int y, RColor *color)
  71 {
  72     unsigned char *ptr;
  73
  74     assert(image!=NULL);
  75     assert(color!=NULL);
  76     if (x < 0 || x >= image->width || y < 0 || y >= image->height)
  77         return;
  78
  79     if (image->format == RRGBAFormat) {
  80         ptr = image->data + (y*image->width + x) * 4;
  81     } else {
  82         ptr = image->data + (y*image->width + x) * 3;
  83     }
  84
  85     if (color->alpha==255) {
  86         *ptr++ = color->red;
  87         *ptr++ = color->green;
  88         *ptr++ = color->blue;
  89         if (image->format == RRGBAFormat) {
  90             *ptr = 255;
  91         }
  92     } else {
  93         register int alpha, nalpha, r, g, b;
  94
  95         r = color->red;
  96         g = color->green;
  97         b = color->blue;
  98         alpha = color->alpha;
  99         nalpha = 255 - alpha;
 100
 101         *ptr = (((int)*ptr * nalpha) + (r * alpha))/256; ptr++;
 102         *ptr = (((int)*ptr * nalpha) + (g * alpha))/256; ptr++;
 103         *ptr = (((int)*ptr * nalpha) + (b * alpha))/256; ptr++;
 104         if (image->format == RRGBAFormat) {
 105             *ptr = alpha + ((int)*ptr * nalpha)/256;
 106         }
 107     }
 108 }
 109
 110
 111 static void
 112 operatePixel(RImage *image, int ofs, int operation, RColor *color)
 113 {
 114     unsigned char *sr, *sg, *sb, *sa;
 115     register int alpha, nalpha, tmp;
 116     int hasAlpha = image->format == RRGBAFormat;
 117
 118     alpha = color->alpha;
 119     nalpha = 255 - alpha;
 120
 121     sr = image->data + ofs*(hasAlpha ? 4 : 3);
 122     sg = image->data + ofs*(hasAlpha ? 4 : 3) + 1;
 123     sb = image->data + ofs*(hasAlpha ? 4 : 3) + 2;
 124     sa = image->data + ofs*(hasAlpha ? 4 : 3) + 3;
 125
 126     switch (operation) {
 127      case RClearOperation:
 128         *sr = 0;
 129         *sg = 0;
 130         *sb = 0;
 131         if (hasAlpha)
 132             *sa = 0;
 133         break;
 134      case RCopyOperation:
 135         *sr = color->red;
 136         *sg = color->green;
 137         *sb = color->blue;
 138         if (hasAlpha)
 139             *sa = color->alpha;
 140         break;
 141      case RNormalOperation:
 142         if (color->alpha==255) {
 143             *sr = color->red;
 144             *sg = color->green;
 145             *sb = color->blue;
 146             if (hasAlpha)
 147                 *sa = 255;
 148         } else {
 149             *sr = (((int)*sr * nalpha) + ((int)color->red * alpha))/256;
 150             *sg = (((int)*sg * nalpha) + ((int)color->green * alpha))/256;
 151             *sb = (((int)*sb * nalpha) + ((int)color->blue * alpha))/256;
 152         }
 153         break;
 154      case RAddOperation:
 155         tmp = color->red + *sr;
 156         *sr = MIN(255, tmp);
 157         tmp = color->green + *sg;
 158         *sg = MIN(255, tmp);
 159         tmp = color->blue + *sb;
 160         *sb = MIN(255, tmp);
 161         if (hasAlpha)
 162             *sa = MIN(*sa, color->alpha);
 163         break;
 164      case RSubtractOperation:
 165         tmp = *sr - color->red;
 166         *sr = MAX(0, tmp);
 167         tmp = *sg - color->green;
 168         *sg = MAX(0, tmp);
 169         tmp = *sb - color->blue;
 170         *sb = MAX(0, tmp);
 171         if (hasAlpha)
 172             *sa = MIN(*sa, color->alpha);
 173         break;
 174     }
 175 }
 176
 177
 178
 179 void
 180 ROperatePixel(RImage *image, int operation, int x, int y, RColor *color)
 181 {
 182     int ofs;
 183
 184     assert(image!=NULL);
 185     assert(color!=NULL);
 186     assert(x >= 0 && x < image->width);
 187     assert(y >= 0 && y < image->height);
 188
 189     ofs = y*image->width + x;
 190
 191     operatePixel(image, ofs, operation, color);
 192 }
 193
 194
 195 void
 196 RPutPixels(RImage *image, RPoint *points, int npoints, int mode, RColor *color)
 197 {
 198     register int x, y, i;
 199
 200     assert(image!=NULL);
 201     assert(points!=NULL);
 202
 203     x = y = 0;
 204
 205     for (i=0; i<npoints; i++) {
 206         if (mode == RAbsoluteCoordinates) {
 207             x = points[i].x;
 208             y = points[i].y;
 209         } else {
 210             x += points[i].x;
 211             y += points[i].y;
 212         }
 213         RPutPixel(image, x, y, color);
 214     }
 215 }
 216
 217
 218 void
 219 ROperatePixels(RImage *image, int operation, RPoint *points, int npoints,
 220                int mode, RColor *color)
 221 {
 222     register int x, y, i;
 223
 224     assert(image!=NULL);
 225     assert(points!=NULL);
 226
 227     x = y = 0;
 228
 229     for (i=0; i<npoints; i++) {
 230         if (mode == RAbsoluteCoordinates) {
 231             x = points[i].x;
 232             y = points[i].y;
 233         } else {
 234             x += points[i].x;
 235             y += points[i].y;
 236         }
 237         ROperatePixel(image, operation, x, y, color);
 238     }
 239 }
 240
 241
 242 static Bool
 243 clipLineInRectangle(int xmin, int ymin, int xmax, int ymax,
 244                     int *x1, int *y1, int *x2, int *y2)
 245 {
 246 #define TOP     (1<<0)
 247 #define BOT     (1<<1)
 248 #define LEF     (1<<2)
 249 #define RIG     (1<<3)
 250 #define CHECK_OUT(X,Y)  (((Y) > ymax ? TOP : ((Y) < ymin ? BOT : 0))\
 251                          | ((X) > xmax ? RIG : ((X) < xmin ? LEF : 0)))
 252
 253     int ocode1, ocode2, ocode;
 254     int accept = 0;
 255     int x, y;
 256
 257     ocode1 = CHECK_OUT(*x1, *y1);
 258     ocode2 = CHECK_OUT(*x2, *y2);
 259
 260     for(;;) {
 261         if (!ocode1 && !ocode2) { /* completely inside */
 262             accept = 1;
 263             break;
 264         } else if (ocode1 & ocode2) {
 265             break;
 266         }
 267
 268         if (ocode1)
 269             ocode = ocode1;
 270         else
 271             ocode = ocode2;
 272
 273         if (ocode & TOP) {
 274             x = *x1 + (*x2 - *x1) * (ymax - *y1) / (*y2 - *y1);
 275             y = ymax;
 276         } else if (ocode & BOT) {
 277             x = *x1 + (*x2 - *x1) * (ymin - *y1) / (*y2 - *y1);
 278             y = ymin;
 279         } else if (ocode & RIG) {
 280             y = *y1 + (*y2 - *y1) * (xmax - *x1) / (*x2 - *x1);
 281             x = xmax;
 282         } else if (ocode & LEF) {
 283             y = *y1 + (*y2 - *y1) * (xmax - *x1) / (*x2 - *x1);
 284             x = xmin;
 285         }
 286
 287         if (ocode == ocode1) {
 288             *x1 = x;
 289             *y1 = y;
 290             ocode1 = CHECK_OUT(x, y);
 291         } else {
 292             *x2 = x;
 293             *y2 = y;
 294             ocode2 = CHECK_OUT(x, y);
 295         }
 296     }
 297
 298     return accept;
 299 }
 300
 301
 302 /*
 303  * This routine is a generic drawing routine, based on Bresenham's line
 304  * drawing algorithm.
 305  */
 306 static int
 307 genericLine(RImage *image, int x0, int y0, int x1, int y1, RColor *color,
 308             int operation, int polyline)
 309 {
 310     int i, err, du, dv, du2, dv2, uofs, vofs, last;
 311
 312     assert(image!=NULL);
 313
 314     if (!clipLineInRectangle(0, 0, image->width-1, image->height-1,
 315                              &x0, &y0, &x1, &y1))
 316         return True;
 317
 318     if (x0 < x1) {
 319         du = x1 - x0;
 320         uofs = 1;
 321     } else {
 322         du = x0 - x1;
 323         uofs = -1;
 324     }
 325     if (y0 < y1) {
 326         dv = y1 -y0;
 327         vofs = image->width;
 328     } else {
 329         dv = y0 - y1;
 330         vofs = -image->width;
 331     }
 332
 333     if (du < dv) {
 334         /* Swap coordinates between them, so that always du>dv */
 335         i = du; du = dv; dv = i;
 336         i = uofs; uofs = vofs; vofs = i;
 337     }
 338
 339     err = 0;
 340     du2 = du<<1;
 341     dv2 = dv<<1;
 342     last = (polyline) ? du-1 : du;
 343
 344     if (color->alpha==255 || operation==RCopyOperation) {
 345         unsigned char *ptr;
 346
 347         if (image->format == RRGBAFormat)
 348             i = (y0*image->width + x0) * 4;
 349         else
 350             i = (y0*image->width + x0) * 3;
 351         ptr = image->data + i;
 352
 353         for (i=0; i<=last; i++) {
 354             /* Draw the pixel */
 355             *ptr = color->red;
 356             *(ptr+1) = color->green;
 357             *(ptr+2) = color->blue;
 358             if (image->format == RRGBAFormat)
 359                 *(ptr+3) = 255;
 360
 361             /* Compute error for NeXT Step */
 362             err += dv2;
 363             if (err >= du) {
 364                 if (image->format == RRGBAFormat)
 365                     ptr += vofs*4;
 366                 else
 367                     ptr += vofs*3;
 368                 err -= du2;
 369             }
 370             if (image->format == RRGBAFormat)
 371                 ptr += uofs*4;
 372             else
 373                 ptr += uofs*3;
 374         }
 375     } else {
 376         register int ofs = y0*image->width + x0;
 377
 378         for (i=0; i<=last; i++) {
 379             /* Draw the pixel */
 380             operatePixel(image, ofs, operation, color);
 381
 382             /* Compute error for NeXT Step */
 383             err += dv2;
 384             if (err >= du) {
 385                 ofs += vofs;
 386                 err -= du2;
 387             }
 388             ofs += uofs;
 389         }
 390     }
 391
 392 #if 0
 393     if (mode == RALTER_PIXELS) {
 394         RColorOffset *cdelta = (RColorOffset*)cdata;
 395         register short r, g, b, a;
 396
 397         for (i=0; i<=last; i++) {
 398             /* Change the pixel with offset */
 399             r = (short)*sr + cdelta->red;
 400             g = (short)*sg + cdelta->green;
 401             b = (short)*sb + cdelta->blue;
 402             if (r>255) r = 255; else if (r<0) r = 0;
 403             if (g>255) g = 255; else if (g<0) g = 0;
 404             if (b>255) b = 255; else if (b<0) b = 0;
 405             *sr = (unsigned char) r;
 406             *sg = (unsigned char) g;
 407             *sb = (unsigned char) b;
 408             if (image->data[3]) {
 409                 a = (short)*sa + cdelta->alpha;
 410                 if (a>255) a = 255; else if (a<0) a = 0;
 411                 *sa = (unsigned char) a;
 412             }
 413
 414             /* Compute error for NeXT Step */
 415             err += dv2;
 416             if (err >= du) {
 417                 sr += vofs; sg += vofs;
 418                 sb += vofs; sa += vofs;
 419                 err -= du2;
 420             }
 421             sr += uofs; sg += uofs;
 422             sb += uofs; sa += uofs;
 423         }
 424     } else {
 425         RColor *color = (RColor*)cdata;
 426
 427         if (color->alpha==255) {
 428             for (i=0; i<=last; i++) {
 429                 /* Draw the pixel */
 430                 *sr = color->red;
 431                 *sg = color->green;
 432                 *sb = color->blue;
 433                 if (image->data[3])
 434                     *sa = 255;
 435
 436                 /* Compute error for NeXT Step */
 437                 err += dv2;
 438                 if (err >= du) {
 439                     sr += vofs; sg += vofs;
 440                     sb += vofs; sa += vofs;
 441                     err -= du2;
 442                 }
 443                 sr += uofs; sg += uofs;
 444                 sb += uofs; sa += uofs;
 445             }
 446         } else {
 447             register short alpha, nalpha, r, g ,b;
 448
 449             alpha = color->alpha;
 450             nalpha = 255 - alpha;
 451             r = color->red;
 452             g = color->green;
 453             b = color->blue;
 454
 455             for (i=0; i<=last; i++) {
 456                 /* Draw the pixel */
 457                 *sr = (((int)*sr * nalpha) + (r * alpha))/256;
 458                 *sg = (((int)*sg * nalpha) + (g * alpha))/256;
 459                 *sb = (((int)*sb * nalpha) + (b * alpha))/256;
 460                 if (image->data[3])
 461                     *sa = alpha + ((int)*sa * nalpha)/256;
 462
 463                 /* Compute error for NeXT Step */
 464                 err += dv2;
 465                 if (err >= du) {
 466                     sr += vofs; sg += vofs;
 467                     sb += vofs; sa += vofs;
 468                     err -= du2;
 469                 }
 470                 sr += uofs; sg += uofs;
 471                 sb += uofs; sa += uofs;
 472             }
 473         }
 474     }
 475 #endif
 476     return True;
 477 }
 478
 479
 480 int
 481 RDrawLine(RImage *image, int x0, int y0, int x1, int y1, RColor *color)
 482 {
 483     return genericLine(image, x0, y0, x1, y1, color, RNormalOperation, False);
 484 }
 485
 486
 487 int
 488 ROperateLine(RImage *image, int operation, int x0, int y0, int x1,
 489              int y1, RColor *color)
 490 {
 491     return genericLine(image, x0, y0, x1, y1, color, operation, False);
 492 }
 493
 494
 495 void
 496 RDrawLines(RImage *image, RPoint *points, int npoints, int mode, RColor *color)
 497 {
 498     register int x1, y1, x2, y2, i;
 499
 500     assert(points!=NULL);
 501
 502     if (npoints==0)
 503         return;
 504
 505     x1 = points[0].x;
 506     y1 = points[0].y;
 507     x2 = y2 = 0;
 508
 509     for (i=1; i<npoints-1; i++) {
 510         if (mode == RAbsoluteCoordinates) {
 511             x2 = points[i].x;
 512             y2 = points[i].y;
 513         } else {
 514             x2 += points[i-1].x;
 515             y2 += points[i-1].y;
 516         }
 517         /* Don't draw pixels at junction points twice */
 518         genericLine(image, x1, y1, x2, y2, color, RNormalOperation, True);
 519         x1 = x2;
 520         y1 = y2;
 521     }
 522     i = npoints-1; /* last point */
 523     if (mode == RAbsoluteCoordinates) {
 524         x2 = points[i].x;
 525         y2 = points[i].y;
 526     } else {
 527         x2 += points[i-1].x;
 528         y2 += points[i-1].y;
 529     }
 530     i = (points[0].x==x2 && points[0].y==y2 && npoints>1);
 531     genericLine(image, x1, y1, x2, y2, color, RNormalOperation, i);
 532 }
 533
 534
 535 void
 536 ROperateLines(RImage *image, int operation, RPoint *points,
 537                         int npoints, int mode, RColor *color)
 538 {
 539     register int x1, y1, x2, y2, i;
 540
 541     assert(points!=NULL);
 542
 543     if (npoints==0)
 544         return;
 545
 546     x1 = points[0].x;
 547     y1 = points[0].y;
 548     x2 = y2 = 0;
 549
 550     for (i=1; i<npoints-1; i++) {
 551         if (mode == RAbsoluteCoordinates) {
 552             x2 = points[i].x;
 553             y2 = points[i].y;
 554         } else {
 555             x2 += points[i-1].x;
 556             y2 += points[i-1].y;
 557         }
 558         /* Don't draw pixels at junction points twice */
 559         genericLine(image, x1, y1, x2, y2, color, operation, True);
 560         x1 = x2;
 561         y1 = y2;
 562     }
 563     i = npoints-1; /* last point */
 564     if (mode == RAbsoluteCoordinates) {
 565         x2 = points[i].x;
 566         y2 = points[i].y;
 567     } else {
 568         x2 += points[i-1].x;
 569         y2 += points[i-1].y;
 570     }
 571     i = (points[0].x==x2 && points[0].y==y2 && npoints>1);
 572     genericLine(image, x1, y1, x2, y2, color, operation, i);
 573 }
 574
 575
 576 void
 577 RDrawSegments(RImage *image, RSegment *segs, int nsegs, RColor *color)
 578 {
 579     register int i;
 580
 581     assert(segs!=NULL);
 582
 583     for (i=0; i<nsegs; i++) {
 584         genericLine(image, segs->x1, segs->y1, segs->x2, segs->y2, color,
 585                     RNormalOperation, False);
 586         segs++;
 587     }
 588 }
 589
 590
 591 void
 592 ROperateSegments(RImage *image, int operation, RSegment *segs,
 593                  int nsegs, RColor *color)
 594 {
 595     register int i;
 596
 597     assert(segs!=NULL);
 598
 599     for (i=0; i<nsegs; i++) {
 600         genericLine(image, segs->x1, segs->y1, segs->x2, segs->y2, color,
 601                     operation, False);
 602         segs++;
 603     }
 604 }
 605