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[wxWidgets.git] / src / common / imaggif.cpp
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1/////////////////////////////////////////////////////////////////////////////
2// Name: imaggif.cpp
3// Purpose: wxGIFHandler
4// Author: Guillermo Rodriguez Garcia
5// wxWindows adaptation by Vaclav Slavik
6// Licence: wxWindows licence
7/////////////////////////////////////////////////////////////////////////////
8
9#ifdef __GNUG__
10#pragma implementation "imaggif.h"
11#endif
12
13// For compilers that support precompilation, includes "wx.h".
14#include <wx/wxprec.h>
15
16#ifdef __BORLANDC__
17#pragma hdrstop
18#endif
19
20#include <wx/wx.h>
21
22#include <wx/image.h>
23#include <wx/wfstream.h>
24#include <wx/module.h>
25
26#include <wx/imaggif.h>
27
28/*
29
30FOLLOWING CODE IS BY G.R.G. :
31(except wxInputStream stuff)
32
33*/
34
35/************************************************************************
e207152c 36 READGIF.H - Reads a GIF file
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37 ------------------------------------------------------------------------
38 Guillermo Rodriguez Garcia
39 <guille@iies.es>
40
99cc0158 41 Version: 2.1
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42*************************************************************************/
43
e207152c 44
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45typedef struct
46{
47 int w; /* width */
48 int h; /* height */
99cc0158 49 int transparent; /* transparent color (-1 = none) */
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50 unsigned char *p; /* bitmap */
51 unsigned char *pal; /* palette */
52} IMAGEN;
53
54
e207152c 55
b59bf2db 56/************************************************************************
e207152c 57 READGIF.C - Reads a GIF file
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58 ------------------------------------------------------------------------
59 Guillermo Rodriguez Garcia
60 <guille@iies.es>
61
99cc0158 62 Version: 2.1
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63*************************************************************************/
64
65
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66#include <stdlib.h>
67#include <string.h>
68
69
70/* error codes */
71#define E_OK 0 /* everything was OK */
72#define E_ARCHIVO -1 /* error opening file */
73#define E_FORMATO -2 /* error in gif header */
74#define E_MEMORIA -3 /* error allocating memory */
75
76
77/* This class binding is by VS, so all bugs in it are mine ;-) */
78
79class gifDecoder
80{
81 private:
82 /* globals */
83 int restbits; /* remaining valid bits */
84 unsigned int restbyte; /* remaining bytes in this block */
85 unsigned int lastbyte; /* last byte read */
86
53b7ce7e 87 wxInputStream *f; /* input file */
b59bf2db 88
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89 public:
90 gifDecoder(wxInputStream *s) { f = s; }
91 int getcode(int bits);
92 int dgif(IMAGEN *img, int interl, int bits);
93 int readgif(IMAGEN *img);
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94};
95
96
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97
98/* getcode:
99 * Reads the next code from the file, with size 'bits'
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100 */
101int gifDecoder::getcode(int bits)
102{
103 unsigned int mask; /* bit mask */
104 unsigned int code; /* code (result) */
105
106
107 /* get remaining bits from last byte read */
108 mask = (1 << bits) - 1;
109 code = (lastbyte >> (8 - restbits)) & mask;
110
e207152c 111 /* keep reading new bytes while needed */
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112 while (bits > restbits)
113 {
114 /* if no bytes left in this block, read the next block */
115 if (restbyte == 0)
e207152c 116 restbyte = (unsigned char)f->GetC();
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117
118 /* read next byte and isolate the bits we need */
e207152c 119 lastbyte = (unsigned char)f->GetC();
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120 mask = (1 << (bits - restbits)) - 1;
121 code = code + ((lastbyte & mask) << restbits);
122 restbyte--;
123
124 /* adjust total number of bits extracted from the buffer */
125 restbits = restbits + 8;
126 }
e207152c 127
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128 /* find number of bits reamining for next code */
129 restbits = (restbits - bits);
130
131 return code;
132}
133
53b7ce7e 134
e207152c 135
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136/* dgif:
137 * GIF decoding function. The initial code size (aka root size)
138 * is 'bits'. Supports interlaced images (interl == 1).
139 */
140int gifDecoder::dgif(IMAGEN *img, int interl, int bits)
141{
142 int ab_prefix[4096]; /* alphabet (prefixes) */
143 int ab_tail[4096]; /* alphabet (tails) */
144 int stack[4096]; /* decompression stack */
145
146 int ab_clr; /* clear code */
147 int ab_fin; /* end of info code */
148 int ab_bits; /* actual symbol width, in bits */
149 int ab_free; /* first free position in alphabet */
150 int ab_max; /* last possible character in alphabet */
151 int pass; /* pass number in interlaced images */
152 int pos; /* index into decompresion stack */
153 int x, y; /* position in image buffer */
154
155 int code, readcode, lastcode, abcabca;
156
157 /* these won't change */
158 ab_clr = (1 << bits);
159 ab_fin = (1 << bits) + 1;
160
161 /* these will change through the decompression proccess */
162 ab_bits = bits + 1;
163 ab_free = (1 << bits) + 2;
164 ab_max = (1 << ab_bits) - 1;
165 lastcode = -1;
166 abcabca = -1;
167 pass = 1;
168 pos = x = y = 0;
169
170 /* reset static globals */
171 restbits = 0;
172 restbyte = 0;
173 lastbyte = 0;
174
175 do
176 {
177 /* get next code */
178 readcode = code = getcode(ab_bits);
179
180 /* end of image? */
181 if (code == ab_fin) break;
182
183 /* reset alphabet? */
184 if (code == ab_clr)
185 {
186 /* reset main variables */
187 ab_bits = bits + 1;
188 ab_free = (1 << bits) + 2;
189 ab_max = (1 << ab_bits) - 1;
190 lastcode = -1;
191 abcabca = -1;
192
193 /* skip to next code */
194 continue;
195 }
196
197 /* unknown code: special case (like in ABCABCA) */
198 if (code >= ab_free)
199 {
200 code = lastcode; /* take last string */
201 stack[pos++] = abcabca; /* add first character */
202 }
203
204 /* build the string for this code in the stack */
205 while (code > ab_clr)
206 {
207 stack[pos++] = ab_tail[code];
208 code = ab_prefix[code];
209 }
210 stack[pos] = code; /* push last code into the stack */
211 abcabca = code; /* save for special case */
212
213 /* make new entry in alphabet (only if NOT just cleared) */
214 if (lastcode != -1)
215 {
216 ab_prefix[ab_free] = lastcode;
217 ab_tail[ab_free] = code;
218 ab_free++;
219
220 if ((ab_free > ab_max) && (ab_bits < 12))
221 {
222 ab_bits++;
223 ab_max = (1 << ab_bits) - 1;
224 }
225 }
226
227 /* dump stack data to the buffer */
228 while (pos >= 0)
229 {
230 (img->p)[x + (y * (img->w))] = (char)stack[pos--];
231
232 if (++x >= (img->w))
233 {
234 x = 0;
235
236 if (interl)
237 {
238 /* support for interlaced images */
239 switch (pass)
240 {
241 case 1: y += 8; break;
242 case 2: y += 8; break;
243 case 3: y += 4; break;
244 case 4: y += 2; break;
245 }
246 if (y >= (img->h))
247 {
248 switch (++pass)
249 {
250 case 2: y = 4; break;
251 case 3: y = 2; break;
252 case 4: y = 1; break;
253 }
254 }
255 }
256 else
257 {
258 /* non-interlaced */
259 y++;
260 }
261 }
262 }
263
264 pos = 0;
265 lastcode = readcode;
266 }
267 while (code != ab_fin);
268
269 return 0;
270}
271
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272
273
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274/* readgif:
275 * Reads a GIF image from the file with filename 'nombre' in the
276 * IMAGEN structure pointed by 'img'. Can read GIFs with any bit
277 * size (color depth), but the output image is always expanded
278 * to 8 bits per pixel. Also, the image palette always contains
279 * 256 colors, although some of them may be unused. Returns E_OK
280 * (== 0) on success, or an error code if something fails. Error
281 * codes are E_ARCHIVO, E_FORMATO, E_MEMORIA (see above).
282 */
283int gifDecoder::readgif(IMAGEN *img)
284{
285 int size, ncolors, bits, interl, i;
286 unsigned char pal[768];
287 unsigned char buf[16];
288
e207152c 289
b59bf2db 290 /* read header and logical screen descriptor block (LSDB) */
e207152c 291 f->Read(buf, 13);
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292
293 /* check GIF signature */
294 if (memcmp(buf, "GIF", 3) != 0) return E_FORMATO;
295
296 /* load global color map if available */
297 if ((buf[10] & 0x80) == 0x80)
298 {
299 ncolors = 2 << (buf[10] & 0x07);
e207152c 300 f->Read(pal, 3 * ncolors);
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301 }
302
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303 /* assume no transparent color */
304 img->transparent = -1;
b59bf2db 305
99cc0158 306 /* skip most extensions */
e207152c 307 while (((unsigned char)f->GetC()) == 0x21) /* separator */
99cc0158 308 {
e207152c 309 if (((unsigned char)f->GetC()) == 0xF9) /* graphic control ext. */
99cc0158 310 {
99cc0158 311 f->Read(buf, 6);
e207152c 312 if (buf[1] & 0x01)
99cc0158 313 img->transparent = buf[4];
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314 }
315 else
e207152c 316 while ((i = (unsigned char)f->GetC()) != 0) /* byte count */
99cc0158 317 f->SeekI(i, wxFromCurrent);
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318 }
319
320 /* read image descriptor block (IDB) */
e207152c 321 f->Read(buf, 9);
b59bf2db 322 img->w = buf[4] + 256 * buf[5];
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323 img->h = buf[6] + 256 * buf[7];
324 size = img->w * img->h;
325 interl = ((buf[8] & 0x40)? 1 : 0);
326
327 /* load local color map if available */
328 if ((buf[8] & 0x80) == 0x80)
329 {
330 ncolors = 2 << (buf[8] & 0x07);
e207152c 331 f->Read(pal, 3 * ncolors);
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332 }
333
334 /* get initial code size from first byte in raster data */
e207152c 335 bits = (unsigned char)f->GetC();
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336
337 /* allocate memory for image and palette */
338 if ((img->p = (unsigned char*) malloc(size)) == NULL) return E_MEMORIA;
339 if ((img->pal = (unsigned char*) malloc(768)) == NULL) return E_MEMORIA;
340
341 /* shift palette to fit VGA 6-bit format */
342 for (i = 0; i < 768; i++)
e207152c 343 (img->pal)[i] = (unsigned char)pal[i]; /* >> 2 not in wxWin */
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344
345 /* decode GIF */
346 dgif(img, interl, bits);
347
348 /* finish successfully :-) */
349 return E_OK;
350}
351
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352
353
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354/*
355
356FOLLOWING CODE IS BY V.S. :
357
358*/
359
360//-----------------------------------------------------------------------------
361// wxGIFHandler
362//-----------------------------------------------------------------------------
363
364IMPLEMENT_DYNAMIC_CLASS(wxGIFHandler,wxImageHandler)
365
366bool wxGIFHandler::LoadFile( wxImage *image, wxInputStream& stream )
367{
368 unsigned char *ptr, *src, *pal;
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369 IMAGEN igif;
370 int i;
371 gifDecoder *decod;
372
373 image->Destroy();
374
53b7ce7e 375 decod = new gifDecoder(&stream);
b59bf2db 376
e207152c 377 if (decod->readgif(&igif) != E_OK) {
3e473156 378 wxLogDebug(_T("Error reading GIF"));
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379 delete decod;
380 return FALSE;
381 }
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382 delete decod;
383
384 image->Create(igif.w, igif.h);
385 if (!image->Ok()) {
386 free(igif.pal);
387 free(igif.p);
388 return FALSE;
389 }
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390
391 ptr = image->GetData();
392 src = igif.p;
393 pal = igif.pal;
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394
395 if (igif.transparent != -1) {
396 for (i = 0; i < 256; i++)
397 if ((pal[3 * i + 0] == 255) && (pal[3 * i + 1] == 0) && (pal[3 * i + 2] == 255)) pal[3 * i + 2] = 254;
398 pal[3 * (igif.transparent) + 0] = 255,
399 pal[3 * (igif.transparent) + 1] = 0,
400 pal[3 * (igif.transparent) + 2] = 255;
401 image->SetMaskColour(255, 0, 255);
402 }
403 else image->SetMask(FALSE);
404
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405 for (i = 0; i < igif.w * igif.h; i++, src++) {
406 *(ptr++) = pal[3 * (*src) + 0];
407 *(ptr++) = pal[3 * (*src) + 1];
408 *(ptr++) = pal[3 * (*src) + 2];
409 }
410
411 free(igif.pal);
412 free(igif.p);
413 return TRUE;
414}
415
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416bool wxGIFHandler::SaveFile( wxImage * WXUNUSED(image),
417 wxOutputStream& WXUNUSED(stream) )
b59bf2db 418{
3e473156 419 wxLogDebug(_T("wxGIFHandler is read-only!!"));
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420 return FALSE;
421}
422
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424
425
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427