1 /* scale.c - image scaling
3 * Raster graphics library
5 * Copyright (c) 1997-2003 Alfredo K. Kojima
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.
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.
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., 675 Mass Ave, Cambridge, MA 02139, USA.
31 #define PI 3.14159265358979323846
39 *----------------------------------------------------------------------
41 * Creates a scaled copy of an image.
44 * The new scaled image.
46 *----------------------------------------------------------------------
48 RImage
*RScaleImage(RImage
* image
, unsigned new_width
, unsigned new_height
)
58 if (new_width
== image
->width
&& new_height
== image
->height
)
59 return RCloneImage(image
);
61 img
= RCreateImage(new_width
, new_height
, image
->format
== RRGBAFormat
);
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
;
75 if (image
->format
== RRGBAFormat
) {
76 for (y
= 0; y
< new_height
; y
++) {
77 t
= image
->width
* (py
>> 16);
79 s
= image
->data
+ (t
<< 2); /* image->data+t*4 */
83 for (x
= 0; x
< new_width
; x
++) {
94 s
+= t
<< 2; /* t*4 */
99 for (y
= 0; y
< new_height
; y
++) {
100 t
= image
->width
* (py
>> 16);
102 s
= image
->data
+ (t
<< 1) + t
; /* image->data+t*3 */
106 for (x
= 0; x
< new_width
; x
++) {
116 s
+= (t
<< 1) + t
; /* t*3 */
126 * Filtered Image Rescaling code copy/pasted from
128 * Public Domain 1991 by Dale Schumacher
132 * filter function definitions
134 #define box_support (0.5)
136 static double box_filter(double t
)
138 if ((t
> -0.5) && (t
<= 0.5))
143 #define triangle_support (1.0)
145 static double triangle_filter(double t
)
154 #define bell_support (1.5)
156 static double bell_filter(double t
) /* box (*) box (*) box */
161 return (.75 - (t
* t
));
164 return (.5 * (t
* t
));
169 #define B_spline_support (2.0)
171 static double B_spline_filter(double t
) /* box (*) box (*) box (*) box */
179 return ((.5 * tt
* t
) - tt
+ (2.0 / 3.0));
182 return ((1.0 / 6.0) * (t
* t
* t
));
187 static double sinc(double x
)
195 #define Lanczos3_support (3.0)
197 static double Lanczos3_filter(double t
)
202 return (sinc(t
) * sinc(t
/ 3.0));
206 #define Mitchell_support (2.0)
208 #define B (1.0 / 3.0)
209 #define C (1.0 / 3.0)
211 static double Mitchell_filter(double t
)
219 t
= (((12.0 - 9.0 * B
- 6.0 * C
) * (t
* tt
))
220 + ((-18.0 + 12.0 * B
+ 6.0 * C
) * tt
)
223 } else if (t
< 2.0) {
224 t
= (((-1.0 * B
- 6.0 * C
) * (t
* tt
))
225 + ((6.0 * B
+ 30.0 * C
) * tt
)
226 + ((-12.0 * B
- 48.0 * C
) * t
)
227 + (8.0 * B
+ 24 * C
));
233 static double (*filterf
)(double) = Mitchell_filter
;
234 static double fwidth
= Mitchell_support
;
236 void _wraster_change_filter(int type
)
240 filterf
= box_filter
;
241 fwidth
= box_support
;
243 case RTriangleFilter
:
244 filterf
= triangle_filter
;
245 fwidth
= triangle_support
;
248 filterf
= bell_filter
;
249 fwidth
= bell_support
;
252 filterf
= B_spline_filter
;
253 fwidth
= B_spline_support
;
255 case RLanczos3Filter
:
256 filterf
= Lanczos3_filter
;
257 fwidth
= Lanczos3_support
;
260 case RMitchellFilter
:
261 filterf
= Mitchell_filter
;
262 fwidth
= Mitchell_support
;
268 * image rescaling routine
277 int n
; /* number of contributors */
278 CONTRIB
*p
; /* pointer to list of contributions */
281 CLIST
*contrib
; /* array of contribution lists */
283 /* clamp the input to the specified range */
284 #define CLAMP(v,l,h) ((v)<(l) ? (l) : (v) > (h) ? (h) : v)
286 /* return of calloc is not checked if NULL in the function below! */
287 RImage
*RSmoothScaleImage(RImage
* src
, unsigned new_width
, unsigned new_height
)
289 RImage
*tmp
; /* intermediate image */
290 double xscale
, yscale
; /* zoom scale factors */
291 int i
, j
, k
; /* loop variables */
292 int n
; /* pixel number */
293 double center
, left
, right
; /* filter calculation variables */
294 double width
, fscale
; /* filter calculation variables */
295 double rweight
, gweight
, bweight
;
299 int sch
= src
->format
== RRGBAFormat
? 4 : 3;
301 dst
= RCreateImage(new_width
, new_height
, False
);
303 /* create intermediate image to hold horizontal zoom */
304 tmp
= RCreateImage(dst
->width
, src
->height
, False
);
305 xscale
= (double)new_width
/ (double)src
->width
;
306 yscale
= (double)new_height
/ (double)src
->height
;
308 /* pre-calculate filter contributions for a row */
309 contrib
= (CLIST
*) calloc(new_width
, sizeof(CLIST
));
311 width
= fwidth
/ xscale
;
312 fscale
= 1.0 / xscale
;
313 for (i
= 0; i
< new_width
; ++i
) {
315 contrib
[i
].p
= (CONTRIB
*) calloc((int) ceil(width
* 2 + 1), sizeof(CONTRIB
));
316 center
= (double)i
/ xscale
;
317 left
= ceil(center
- width
);
318 right
= floor(center
+ width
);
319 for (j
= left
; j
<= right
; ++j
) {
320 rweight
= center
- (double)j
;
321 rweight
= (*filterf
) (rweight
/ fscale
) / fscale
;
324 } else if (j
>= src
->width
) {
325 n
= (src
->width
- j
) + src
->width
- 1;
330 contrib
[i
].p
[k
].pixel
= n
* sch
;
331 contrib
[i
].p
[k
].weight
= rweight
;
336 for (i
= 0; i
< new_width
; ++i
) {
338 contrib
[i
].p
= (CONTRIB
*) calloc((int) ceil(fwidth
* 2 + 1), sizeof(CONTRIB
));
339 center
= (double)i
/ xscale
;
340 left
= ceil(center
- fwidth
);
341 right
= floor(center
+ fwidth
);
342 for (j
= left
; j
<= right
; ++j
) {
343 rweight
= center
- (double)j
;
344 rweight
= (*filterf
) (rweight
);
347 } else if (j
>= src
->width
) {
348 n
= (src
->width
- j
) + src
->width
- 1;
353 contrib
[i
].p
[k
].pixel
= n
* sch
;
354 contrib
[i
].p
[k
].weight
= rweight
;
359 /* apply filter to zoom horizontally from src to tmp */
362 for (k
= 0; k
< tmp
->height
; ++k
) {
365 sp
= src
->data
+ src
->width
* k
* sch
;
367 for (i
= 0; i
< tmp
->width
; ++i
) {
368 rweight
= gweight
= bweight
= 0.0;
372 for (j
= 0; j
< contrib
[i
].n
; ++j
) {
373 rweight
+= sp
[pp
[j
].pixel
] * pp
[j
].weight
;
374 gweight
+= sp
[pp
[j
].pixel
+ 1] * pp
[j
].weight
;
375 bweight
+= sp
[pp
[j
].pixel
+ 2] * pp
[j
].weight
;
377 *p
++ = CLAMP(rweight
, 0, 255);
378 *p
++ = CLAMP(gweight
, 0, 255);
379 *p
++ = CLAMP(bweight
, 0, 255);
383 /* free the memory allocated for horizontal filter weights */
384 for (i
= 0; i
< tmp
->width
; ++i
) {
389 /* pre-calculate filter contributions for a column */
390 contrib
= (CLIST
*) calloc(dst
->height
, sizeof(CLIST
));
392 width
= fwidth
/ yscale
;
393 fscale
= 1.0 / yscale
;
394 for (i
= 0; i
< dst
->height
; ++i
) {
396 contrib
[i
].p
= (CONTRIB
*) calloc((int) ceil(width
* 2 + 1), sizeof(CONTRIB
));
397 center
= (double)i
/ yscale
;
398 left
= ceil(center
- width
);
399 right
= floor(center
+ width
);
400 for (j
= left
; j
<= right
; ++j
) {
401 rweight
= center
- (double)j
;
402 rweight
= (*filterf
) (rweight
/ fscale
) / fscale
;
405 } else if (j
>= tmp
->height
) {
406 n
= (tmp
->height
- j
) + tmp
->height
- 1;
411 contrib
[i
].p
[k
].pixel
= n
* 3;
412 contrib
[i
].p
[k
].weight
= rweight
;
416 for (i
= 0; i
< dst
->height
; ++i
) {
418 contrib
[i
].p
= (CONTRIB
*) calloc((int) ceil(fwidth
* 2 + 1), sizeof(CONTRIB
));
419 center
= (double)i
/ yscale
;
420 left
= ceil(center
- fwidth
);
421 right
= floor(center
+ fwidth
);
422 for (j
= left
; j
<= right
; ++j
) {
423 rweight
= center
- (double)j
;
424 rweight
= (*filterf
) (rweight
);
427 } else if (j
>= tmp
->height
) {
428 n
= (tmp
->height
- j
) + tmp
->height
- 1;
433 contrib
[i
].p
[k
].pixel
= n
* 3;
434 contrib
[i
].p
[k
].weight
= rweight
;
439 /* apply filter to zoom vertically from tmp to dst */
440 sp
= malloc(tmp
->height
* 3);
442 for (k
= 0; k
< new_width
; ++k
) {
445 p
= dst
->data
+ k
* 3;
447 /* copy a column into a row */
450 unsigned char *p
, *d
;
453 for (i
= tmp
->height
, p
= tmp
->data
+ k
* 3; i
-- > 0; p
+= tmp
->width
* 3) {
459 for (i
= 0; i
< new_height
; ++i
) {
460 rweight
= gweight
= bweight
= 0.0;
464 for (j
= 0; j
< contrib
[i
].n
; ++j
) {
465 rweight
+= sp
[pp
[j
].pixel
] * pp
[j
].weight
;
466 gweight
+= sp
[pp
[j
].pixel
+ 1] * pp
[j
].weight
;
467 bweight
+= sp
[pp
[j
].pixel
+ 2] * pp
[j
].weight
;
469 *p
= CLAMP(rweight
, 0, 255);
470 *(p
+ 1) = CLAMP(gweight
, 0, 255);
471 *(p
+ 2) = CLAMP(bweight
, 0, 255);
477 /* free the memory allocated for vertical filter weights */
478 for (i
= 0; i
< dst
->height
; ++i
) {