wrlib/scale.c

   1 /* scale.c - image scaling
   2  *
   3  * Raster graphics library
   4  *
   5  * Copyright (c) 1997-2003 Alfredo K. Kojima
   6  *
   7  *  This library is free software; you can redistribute it and/or
   8  *  modify it under the terms of the GNU Library General Public
   9  *  License as published by the Free Software Foundation; either
  10  *  version 2 of the License, or (at your option) any later version.
  11  *
  12  *  This library is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  *  Library General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU Library General Public
  18  *  License along with this library; if not, write to the Free
  19  *  Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
  20  *  MA 02110-1301, USA.
  21  */
  22
  23 #include <config.h>
  24
  25 #include <stdlib.h>
  26 #include <stdio.h>
  27 #include <string.h>
  28 #include <X11/Xlib.h>
  29 #include <math.h>
  30 #include <assert.h>
  31
  32 #include "wraster.h"
  33 #include "scale.h"
  34
  35 /*
  36  *----------------------------------------------------------------------
  37  * RScaleImage--
  38  *      Creates a scaled copy of an image.
  39  *
  40  * Returns:
  41  *      The new scaled image.
  42  *
  43  *----------------------------------------------------------------------
  44  */
  45 RImage *RScaleImage(RImage * image, unsigned new_width, unsigned new_height)
  46 {
  47         int ox;
  48         int px, py;
  49         register int x, y, t;
  50         int dx, dy;
  51         unsigned char *s;
  52         unsigned char *d;
  53         RImage *img;
  54
  55         if (image == NULL)
  56                 return NULL;
  57
  58         if (new_width == image->width && new_height == image->height)
  59                 return RCloneImage(image);
  60
  61         img = RCreateImage(new_width, new_height, image->format == RRGBAFormat);
  62
  63         if (!img)
  64                 return NULL;
  65
  66         /* fixed point math idea taken from Imlib by
  67          * Carsten Haitzler (Rasterman) */
  68         dx = (image->width << 16) / new_width;
  69         dy = (image->height << 16) / new_height;
  70
  71         py = 0;
  72
  73         d = img->data;
  74
  75         if (image->format == RRGBAFormat) {
  76                 for (y = 0; y < new_height; y++) {
  77                         t = image->width * (py >> 16);
  78
  79                         s = image->data + (t << 2);     /* image->data+t*4 */
  80
  81                         ox = 0;
  82                         px = 0;
  83                         for (x = 0; x < new_width; x++) {
  84                                 px += dx;
  85
  86                                 *(d++) = *(s);
  87                                 *(d++) = *(s + 1);
  88                                 *(d++) = *(s + 2);
  89                                 *(d++) = *(s + 3);
  90
  91                                 t = (px - ox) >> 16;
  92                                 ox += t << 16;
  93
  94                                 s += t << 2;    /* t*4 */
  95                         }
  96                         py += dy;
  97                 }
  98         } else {
  99                 for (y = 0; y < new_height; y++) {
 100                         t = image->width * (py >> 16);
 101
 102                         s = image->data + (t << 1) + t; /* image->data+t*3 */
 103
 104                         ox = 0;
 105                         px = 0;
 106                         for (x = 0; x < new_width; x++) {
 107                                 px += dx;
 108
 109                                 *(d++) = *(s);
 110                                 *(d++) = *(s + 1);
 111                                 *(d++) = *(s + 2);
 112
 113                                 t = (px - ox) >> 16;
 114                                 ox += t << 16;
 115
 116                                 s += (t << 1) + t;      /* t*3 */
 117                         }
 118                         py += dy;
 119                 }
 120         }
 121
 122         return img;
 123 }
 124
 125 /*
 126  * Filtered Image Rescaling code copy/pasted from
 127  * Graphics Gems III
 128  * Public Domain 1991 by Dale Schumacher
 129  */
 130
 131 /*
 132  *      filter function definitions
 133  */
 134 #define box_support             (0.5)
 135
 136 static double box_filter(double t)
 137 {
 138         if ((t > -0.5) && (t <= 0.5))
 139                 return (1.0);
 140         return (0.0);
 141 }
 142
 143 #define triangle_support        (1.0)
 144
 145 static double triangle_filter(double t)
 146 {
 147         if (t < 0.0)
 148                 t = -t;
 149         if (t < 1.0)
 150                 return (1.0 - t);
 151         return (0.0);
 152 }
 153
 154 #define bell_support            (1.5)
 155
 156 static double bell_filter(double t)  /* box (*) box (*) box */
 157 {
 158         if (t < 0)
 159                 t = -t;
 160         if (t < .5)
 161                 return (.75 - (t * t));
 162         if (t < 1.5) {
 163                 t = (t - 1.5);
 164                 return (.5 * (t * t));
 165         }
 166         return (0.0);
 167 }
 168
 169 #define B_spline_support        (2.0)
 170
 171 static double B_spline_filter(double t)   /* box (*) box (*) box (*) box */
 172 {
 173         double tt;
 174
 175         if (t < 0)
 176                 t = -t;
 177         if (t < 1) {
 178                 tt = t * t;
 179                 return ((.5 * tt * t) - tt + (2.0 / 3.0));
 180         } else if (t < 2) {
 181                 t = 2 - t;
 182                 return ((1.0 / 6.0) * (t * t * t));
 183         }
 184         return (0.0);
 185 }
 186
 187 static double sinc(double x)
 188 {
 189         /*
 190          * The original code did this:
 191          *   if (x != 0) ...
 192          * This code is unsafe, it should be:
 193          *   if (fabs(x) > EPSILON) ...
 194          *
 195          * But the call to fabs is already done in the *ONLY* function
 196          * that call sinc: 'Lanczos3_filter'
 197          *
 198          * The goal was to avoid a Divide-by-0 error, now we also
 199          * avoid a +/-inf result too
 200          */
 201         x *= WM_PI;
 202         if (x > 1.0E-9)
 203                 return (sin(x) / x);
 204         return (1.0);
 205 }
 206
 207 #define Lanczos3_support        (3.0)
 208
 209 static double Lanczos3_filter(double t)
 210 {
 211         if (t < 0)
 212                 t = -t;
 213         if (t < 3.0)
 214                 return (sinc(t) * sinc(t / 3.0));
 215         return (0.0);
 216 }
 217
 218 #define Mitchell_support        (2.0)
 219
 220 #define B       (1.0 / 3.0)
 221 #define C       (1.0 / 3.0)
 222
 223 static double Mitchell_filter(double t)
 224 {
 225         double tt;
 226
 227         tt = t * t;
 228         if (t < 0)
 229                 t = -t;
 230         if (t < 1.0) {
 231                 t = (((12.0 - 9.0 * B - 6.0 * C) * (t * tt))
 232                      + ((-18.0 + 12.0 * B + 6.0 * C) * tt)
 233                      + (6.0 - 2 * B));
 234                 return (t / 6.0);
 235         } else if (t < 2.0) {
 236                 t = (((-1.0 * B - 6.0 * C) * (t * tt))
 237                      + ((6.0 * B + 30.0 * C) * tt)
 238                      + ((-12.0 * B - 48.0 * C) * t)
 239                      + (8.0 * B + 24 * C));
 240                 return (t / 6.0);
 241         }
 242         return (0.0);
 243 }
 244
 245 static double (*filterf)(double) = Mitchell_filter;
 246 static double fwidth = Mitchell_support;
 247
 248 void wraster_change_filter(RScalingFilter type)
 249 {
 250         switch (type) {
 251         case RBoxFilter:
 252                 filterf = box_filter;
 253                 fwidth = box_support;
 254                 break;
 255         case RTriangleFilter:
 256                 filterf = triangle_filter;
 257                 fwidth = triangle_support;
 258                 break;
 259         case RBellFilter:
 260                 filterf = bell_filter;
 261                 fwidth = bell_support;
 262                 break;
 263         case RBSplineFilter:
 264                 filterf = B_spline_filter;
 265                 fwidth = B_spline_support;
 266                 break;
 267         case RLanczos3Filter:
 268                 filterf = Lanczos3_filter;
 269                 fwidth = Lanczos3_support;
 270                 break;
 271         default:
 272         case RMitchellFilter:
 273                 filterf = Mitchell_filter;
 274                 fwidth = Mitchell_support;
 275                 break;
 276         }
 277 }
 278
 279 /*
 280  *      image rescaling routine
 281  */
 282
 283 typedef struct {
 284         int pixel;
 285         double weight;
 286 } CONTRIB;
 287
 288 typedef struct {
 289         int n;                  /* number of contributors */
 290         CONTRIB *p;             /* pointer to list of contributions */
 291 } CLIST;
 292
 293 /* clamp the input to the specified range */
 294 #define CLAMP(v,l,h)    ((v)<(l) ? (l) : (v) > (h) ? (h) : v)
 295
 296 /* return of calloc is not checked if NULL in the function below! */
 297 RImage *RSmoothScaleImage(RImage * src, unsigned new_width, unsigned new_height)
 298 {
 299         CLIST *contrib;                 /* array of contribution lists */
 300         RImage *tmp;            /* intermediate image */
 301         double xscale, yscale;  /* zoom scale factors */
 302         int i, j, k;            /* loop variables */
 303         int n;                  /* pixel number */
 304         double center, left, right;     /* filter calculation variables */
 305         double width, fscale;   /* filter calculation variables */
 306         double rweight, gweight, bweight;
 307         RImage *dst;
 308         unsigned char *p;
 309         unsigned char *sp;
 310         int sch = src->format == RRGBAFormat ? 4 : 3;
 311
 312         dst = RCreateImage(new_width, new_height, False);
 313
 314         /* create intermediate image to hold horizontal zoom */
 315         tmp = RCreateImage(dst->width, src->height, False);
 316         xscale = (double)new_width / (double)src->width;
 317         yscale = (double)new_height / (double)src->height;
 318
 319         /* pre-calculate filter contributions for a row */
 320         contrib = (CLIST *) calloc(new_width, sizeof(CLIST));
 321         if (xscale < 1.0) {
 322                 width = fwidth / xscale;
 323                 fscale = 1.0 / xscale;
 324                 for (i = 0; i < new_width; ++i) {
 325                         contrib[i].n = 0;
 326                         contrib[i].p = (CONTRIB *) calloc((int) ceil(width * 2 + 1), sizeof(CONTRIB));
 327                         center = (double)i / xscale;
 328                         left = ceil(center - width);
 329                         right = floor(center + width);
 330                         for (j = left; j <= right; ++j) {
 331                                 rweight = center - (double)j;
 332                                 rweight = (*filterf) (rweight / fscale) / fscale;
 333                                 if (j < 0) {
 334                                         n = -j;
 335                                 } else if (j >= src->width) {
 336                                         n = (src->width - j) + src->width - 1;
 337                                 } else {
 338                                         n = j;
 339                                 }
 340                                 k = contrib[i].n++;
 341                                 contrib[i].p[k].pixel = n * sch;
 342                                 contrib[i].p[k].weight = rweight;
 343                         }
 344                 }
 345         } else {
 346
 347                 for (i = 0; i < new_width; ++i) {
 348                         contrib[i].n = 0;
 349                         contrib[i].p = (CONTRIB *) calloc((int) ceil(fwidth * 2 + 1), sizeof(CONTRIB));
 350                         center = (double)i / xscale;
 351                         left = ceil(center - fwidth);
 352                         right = floor(center + fwidth);
 353                         for (j = left; j <= right; ++j) {
 354                                 rweight = center - (double)j;
 355                                 rweight = (*filterf) (rweight);
 356                                 if (j < 0) {
 357                                         n = -j;
 358                                 } else if (j >= src->width) {
 359                                         n = (src->width - j) + src->width - 1;
 360                                 } else {
 361                                         n = j;
 362                                 }
 363                                 k = contrib[i].n++;
 364                                 contrib[i].p[k].pixel = n * sch;
 365                                 contrib[i].p[k].weight = rweight;
 366                         }
 367                 }
 368         }
 369
 370         /* apply filter to zoom horizontally from src to tmp */
 371         p = tmp->data;
 372
 373         for (k = 0; k < tmp->height; ++k) {
 374                 CONTRIB *pp;
 375
 376                 sp = src->data + src->width * k * sch;
 377
 378                 for (i = 0; i < tmp->width; ++i) {
 379                         rweight = gweight = bweight = 0.0;
 380
 381                         pp = contrib[i].p;
 382
 383                         for (j = 0; j < contrib[i].n; ++j) {
 384                                 rweight += sp[pp[j].pixel] * pp[j].weight;
 385                                 gweight += sp[pp[j].pixel + 1] * pp[j].weight;
 386                                 bweight += sp[pp[j].pixel + 2] * pp[j].weight;
 387                         }
 388                         *p++ = CLAMP(rweight, 0, 255);
 389                         *p++ = CLAMP(gweight, 0, 255);
 390                         *p++ = CLAMP(bweight, 0, 255);
 391                 }
 392         }
 393
 394         /* free the memory allocated for horizontal filter weights */
 395         for (i = 0; i < new_width; ++i) {
 396                 free(contrib[i].p);
 397         }
 398         free(contrib);
 399
 400         /* pre-calculate filter contributions for a column */
 401         contrib = (CLIST *) calloc(dst->height, sizeof(CLIST));
 402         if (yscale < 1.0) {
 403                 width = fwidth / yscale;
 404                 fscale = 1.0 / yscale;
 405                 for (i = 0; i < dst->height; ++i) {
 406                         contrib[i].n = 0;
 407                         contrib[i].p = (CONTRIB *) calloc((int) ceil(width * 2 + 1), sizeof(CONTRIB));
 408                         center = (double)i / yscale;
 409                         left = ceil(center - width);
 410                         right = floor(center + width);
 411                         for (j = left; j <= right; ++j) {
 412                                 rweight = center - (double)j;
 413                                 rweight = (*filterf) (rweight / fscale) / fscale;
 414                                 if (j < 0) {
 415                                         n = -j;
 416                                 } else if (j >= tmp->height) {
 417                                         n = (tmp->height - j) + tmp->height - 1;
 418                                 } else {
 419                                         n = j;
 420                                 }
 421                                 k = contrib[i].n++;
 422                                 contrib[i].p[k].pixel = n * 3;
 423                                 contrib[i].p[k].weight = rweight;
 424                         }
 425                 }
 426         } else {
 427                 for (i = 0; i < dst->height; ++i) {
 428                         contrib[i].n = 0;
 429                         contrib[i].p = (CONTRIB *) calloc((int) ceil(fwidth * 2 + 1), sizeof(CONTRIB));
 430                         center = (double)i / yscale;
 431                         left = ceil(center - fwidth);
 432                         right = floor(center + fwidth);
 433                         for (j = left; j <= right; ++j) {
 434                                 rweight = center - (double)j;
 435                                 rweight = (*filterf) (rweight);
 436                                 if (j < 0) {
 437                                         n = -j;
 438                                 } else if (j >= tmp->height) {
 439                                         n = (tmp->height - j) + tmp->height - 1;
 440                                 } else {
 441                                         n = j;
 442                                 }
 443                                 k = contrib[i].n++;
 444                                 contrib[i].p[k].pixel = n * 3;
 445                                 contrib[i].p[k].weight = rweight;
 446                         }
 447                 }
 448         }
 449
 450         /* apply filter to zoom vertically from tmp to dst */
 451         sp = malloc(tmp->height * 3);
 452
 453         for (k = 0; k < new_width; ++k) {
 454                 CONTRIB *pp;
 455
 456                 p = dst->data + k * 3;
 457
 458                 /* copy a column into a row */
 459                 {
 460                         int i;
 461                         unsigned char *p, *d;
 462
 463                         d = sp;
 464                         for (i = tmp->height, p = tmp->data + k * 3; i-- > 0; p += tmp->width * 3) {
 465                                 *d++ = *p;
 466                                 *d++ = *(p + 1);
 467                                 *d++ = *(p + 2);
 468                         }
 469                 }
 470                 for (i = 0; i < new_height; ++i) {
 471                         rweight = gweight = bweight = 0.0;
 472
 473                         pp = contrib[i].p;
 474
 475                         for (j = 0; j < contrib[i].n; ++j) {
 476                                 rweight += sp[pp[j].pixel] * pp[j].weight;
 477                                 gweight += sp[pp[j].pixel + 1] * pp[j].weight;
 478                                 bweight += sp[pp[j].pixel + 2] * pp[j].weight;
 479                         }
 480                         *p = CLAMP(rweight, 0, 255);
 481                         *(p + 1) = CLAMP(gweight, 0, 255);
 482                         *(p + 2) = CLAMP(bweight, 0, 255);
 483                         p += new_width * 3;
 484                 }
 485         }
 486         free(sp);
 487
 488         /* free the memory allocated for vertical filter weights */
 489         for (i = 0; i < dst->height; ++i) {
 490                 free(contrib[i].p);
 491         }
 492         free(contrib);
 493
 494         RReleaseImage(tmp);
 495
 496         return dst;
 497 }