[LIBJPEG]
[reactos.git] / reactos / dll / 3rdparty / libjpeg / wrgif.c
1 /*
2 * wrgif.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2015 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains routines to write output images in GIF format.
10 *
11 **************************************************************************
12 * NOTE: to avoid entanglements with Unisys' patent on LZW compression, *
13 * this code has been modified to output "uncompressed GIF" files. *
14 * There is no trace of the LZW algorithm in this file. *
15 **************************************************************************
16 *
17 * These routines may need modification for non-Unix environments or
18 * specialized applications. As they stand, they assume output to
19 * an ordinary stdio stream.
20 */
21
22 /*
23 * This code is loosely based on ppmtogif from the PBMPLUS distribution
24 * of Feb. 1991. That file contains the following copyright notice:
25 * Based on GIFENCODE by David Rowley <mgardi@watdscu.waterloo.edu>.
26 * Lempel-Ziv compression based on "compress" by Spencer W. Thomas et al.
27 * Copyright (C) 1989 by Jef Poskanzer.
28 * Permission to use, copy, modify, and distribute this software and its
29 * documentation for any purpose and without fee is hereby granted, provided
30 * that the above copyright notice appear in all copies and that both that
31 * copyright notice and this permission notice appear in supporting
32 * documentation. This software is provided "as is" without express or
33 * implied warranty.
34 *
35 * We are also required to state that
36 * "The Graphics Interchange Format(c) is the Copyright property of
37 * CompuServe Incorporated. GIF(sm) is a Service Mark property of
38 * CompuServe Incorporated."
39 */
40
41 #include "cdjpeg.h" /* Common decls for cjpeg/djpeg applications */
42
43 #ifdef GIF_SUPPORTED
44
45
46 /* Private version of data destination object */
47
48 typedef struct {
49 struct djpeg_dest_struct pub; /* public fields */
50
51 j_decompress_ptr cinfo; /* back link saves passing separate parm */
52
53 /* State for packing variable-width codes into a bitstream */
54 int n_bits; /* current number of bits/code */
55 int maxcode; /* maximum code, given n_bits */
56 INT32 cur_accum; /* holds bits not yet output */
57 int cur_bits; /* # of bits in cur_accum */
58
59 /* State for GIF code assignment */
60 int ClearCode; /* clear code (doesn't change) */
61 int EOFCode; /* EOF code (ditto) */
62 int code_counter; /* counts output symbols */
63
64 /* GIF data packet construction buffer */
65 int bytesinpkt; /* # of bytes in current packet */
66 char packetbuf[256]; /* workspace for accumulating packet */
67
68 } gif_dest_struct;
69
70 typedef gif_dest_struct * gif_dest_ptr;
71
72 /* Largest value that will fit in N bits */
73 #define MAXCODE(n_bits) ((1 << (n_bits)) - 1)
74
75
76 /*
77 * Routines to package finished data bytes into GIF data blocks.
78 * A data block consists of a count byte (1..255) and that many data bytes.
79 */
80
81 LOCAL(void)
82 flush_packet (gif_dest_ptr dinfo)
83 /* flush any accumulated data */
84 {
85 if (dinfo->bytesinpkt > 0) { /* never write zero-length packet */
86 dinfo->packetbuf[0] = (char) dinfo->bytesinpkt++;
87 if (JFWRITE(dinfo->pub.output_file, dinfo->packetbuf, dinfo->bytesinpkt)
88 != (size_t) dinfo->bytesinpkt)
89 ERREXIT(dinfo->cinfo, JERR_FILE_WRITE);
90 dinfo->bytesinpkt = 0;
91 }
92 }
93
94
95 /* Add a character to current packet; flush to disk if necessary */
96 #define CHAR_OUT(dinfo,c) \
97 { (dinfo)->packetbuf[++(dinfo)->bytesinpkt] = (char) (c); \
98 if ((dinfo)->bytesinpkt >= 255) \
99 flush_packet(dinfo); \
100 }
101
102
103 /* Routine to convert variable-width codes into a byte stream */
104
105 LOCAL(void)
106 output (gif_dest_ptr dinfo, int code)
107 /* Emit a code of n_bits bits */
108 /* Uses cur_accum and cur_bits to reblock into 8-bit bytes */
109 {
110 dinfo->cur_accum |= ((INT32) code) << dinfo->cur_bits;
111 dinfo->cur_bits += dinfo->n_bits;
112
113 while (dinfo->cur_bits >= 8) {
114 CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
115 dinfo->cur_accum >>= 8;
116 dinfo->cur_bits -= 8;
117 }
118 }
119
120
121 /* The pseudo-compression algorithm.
122 *
123 * In this module we simply output each pixel value as a separate symbol;
124 * thus, no compression occurs. In fact, there is expansion of one bit per
125 * pixel, because we use a symbol width one bit wider than the pixel width.
126 *
127 * GIF ordinarily uses variable-width symbols, and the decoder will expect
128 * to ratchet up the symbol width after a fixed number of symbols.
129 * To simplify the logic and keep the expansion penalty down, we emit a
130 * GIF Clear code to reset the decoder just before the width would ratchet up.
131 * Thus, all the symbols in the output file will have the same bit width.
132 * Note that emitting the Clear codes at the right times is a mere matter of
133 * counting output symbols and is in no way dependent on the LZW patent.
134 *
135 * With a small basic pixel width (low color count), Clear codes will be
136 * needed very frequently, causing the file to expand even more. So this
137 * simplistic approach wouldn't work too well on bilevel images, for example.
138 * But for output of JPEG conversions the pixel width will usually be 8 bits
139 * (129 to 256 colors), so the overhead added by Clear symbols is only about
140 * one symbol in every 256.
141 */
142
143 LOCAL(void)
144 compress_init (gif_dest_ptr dinfo, int i_bits)
145 /* Initialize pseudo-compressor */
146 {
147 /* init all the state variables */
148 dinfo->n_bits = i_bits;
149 dinfo->maxcode = MAXCODE(dinfo->n_bits);
150 dinfo->ClearCode = (1 << (i_bits - 1));
151 dinfo->EOFCode = dinfo->ClearCode + 1;
152 dinfo->code_counter = dinfo->ClearCode + 2;
153 /* init output buffering vars */
154 dinfo->bytesinpkt = 0;
155 dinfo->cur_accum = 0;
156 dinfo->cur_bits = 0;
157 /* GIF specifies an initial Clear code */
158 output(dinfo, dinfo->ClearCode);
159 }
160
161
162 LOCAL(void)
163 compress_pixel (gif_dest_ptr dinfo, int c)
164 /* Accept and "compress" one pixel value.
165 * The given value must be less than n_bits wide.
166 */
167 {
168 /* Output the given pixel value as a symbol. */
169 output(dinfo, c);
170 /* Issue Clear codes often enough to keep the reader from ratcheting up
171 * its symbol size.
172 */
173 if (dinfo->code_counter < dinfo->maxcode) {
174 dinfo->code_counter++;
175 } else {
176 output(dinfo, dinfo->ClearCode);
177 dinfo->code_counter = dinfo->ClearCode + 2; /* reset the counter */
178 }
179 }
180
181
182 LOCAL(void)
183 compress_term (gif_dest_ptr dinfo)
184 /* Clean up at end */
185 {
186 /* Send an EOF code */
187 output(dinfo, dinfo->EOFCode);
188 /* Flush the bit-packing buffer */
189 if (dinfo->cur_bits > 0) {
190 CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
191 }
192 /* Flush the packet buffer */
193 flush_packet(dinfo);
194 }
195
196
197 /* GIF header construction */
198
199
200 LOCAL(void)
201 put_word (gif_dest_ptr dinfo, unsigned int w)
202 /* Emit a 16-bit word, LSB first */
203 {
204 putc(w & 0xFF, dinfo->pub.output_file);
205 putc((w >> 8) & 0xFF, dinfo->pub.output_file);
206 }
207
208
209 LOCAL(void)
210 put_3bytes (gif_dest_ptr dinfo, int val)
211 /* Emit 3 copies of same byte value --- handy subr for colormap construction */
212 {
213 putc(val, dinfo->pub.output_file);
214 putc(val, dinfo->pub.output_file);
215 putc(val, dinfo->pub.output_file);
216 }
217
218
219 LOCAL(void)
220 emit_header (gif_dest_ptr dinfo, int num_colors, JSAMPARRAY colormap)
221 /* Output the GIF file header, including color map */
222 /* If colormap==NULL, synthesize a grayscale colormap */
223 {
224 int BitsPerPixel, ColorMapSize, InitCodeSize, FlagByte;
225 int cshift = dinfo->cinfo->data_precision - 8;
226 int i;
227
228 if (num_colors > 256)
229 ERREXIT1(dinfo->cinfo, JERR_TOO_MANY_COLORS, num_colors);
230 /* Compute bits/pixel and related values */
231 BitsPerPixel = 1;
232 while (num_colors > (1 << BitsPerPixel))
233 BitsPerPixel++;
234 ColorMapSize = 1 << BitsPerPixel;
235 if (BitsPerPixel <= 1)
236 InitCodeSize = 2;
237 else
238 InitCodeSize = BitsPerPixel;
239 /*
240 * Write the GIF header.
241 * Note that we generate a plain GIF87 header for maximum compatibility.
242 */
243 putc('G', dinfo->pub.output_file);
244 putc('I', dinfo->pub.output_file);
245 putc('F', dinfo->pub.output_file);
246 putc('8', dinfo->pub.output_file);
247 putc('7', dinfo->pub.output_file);
248 putc('a', dinfo->pub.output_file);
249 /* Write the Logical Screen Descriptor */
250 put_word(dinfo, (unsigned int) dinfo->cinfo->output_width);
251 put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
252 FlagByte = 0x80; /* Yes, there is a global color table */
253 FlagByte |= (BitsPerPixel-1) << 4; /* color resolution */
254 FlagByte |= (BitsPerPixel-1); /* size of global color table */
255 putc(FlagByte, dinfo->pub.output_file);
256 putc(0, dinfo->pub.output_file); /* Background color index */
257 putc(0, dinfo->pub.output_file); /* Reserved (aspect ratio in GIF89) */
258 /* Write the Global Color Map */
259 /* If the color map is more than 8 bits precision, */
260 /* we reduce it to 8 bits by shifting */
261 for (i=0; i < ColorMapSize; i++) {
262 if (i < num_colors) {
263 if (colormap != NULL) {
264 if (dinfo->cinfo->out_color_space == JCS_RGB) {
265 /* Normal case: RGB color map */
266 putc(GETJSAMPLE(colormap[0][i]) >> cshift, dinfo->pub.output_file);
267 putc(GETJSAMPLE(colormap[1][i]) >> cshift, dinfo->pub.output_file);
268 putc(GETJSAMPLE(colormap[2][i]) >> cshift, dinfo->pub.output_file);
269 } else {
270 /* Grayscale "color map": possible if quantizing grayscale image */
271 put_3bytes(dinfo, GETJSAMPLE(colormap[0][i]) >> cshift);
272 }
273 } else {
274 /* Create a grayscale map of num_colors values, range 0..255 */
275 put_3bytes(dinfo, (i * 255 + (num_colors-1)/2) / (num_colors-1));
276 }
277 } else {
278 /* fill out the map to a power of 2 */
279 put_3bytes(dinfo, 0);
280 }
281 }
282 /* Write image separator and Image Descriptor */
283 putc(',', dinfo->pub.output_file); /* separator */
284 put_word(dinfo, 0); /* left/top offset */
285 put_word(dinfo, 0);
286 put_word(dinfo, (unsigned int) dinfo->cinfo->output_width); /* image size */
287 put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
288 /* flag byte: not interlaced, no local color map */
289 putc(0x00, dinfo->pub.output_file);
290 /* Write Initial Code Size byte */
291 putc(InitCodeSize, dinfo->pub.output_file);
292
293 /* Initialize for "compression" of image data */
294 compress_init(dinfo, InitCodeSize+1);
295 }
296
297
298 /*
299 * Startup: write the file header.
300 */
301
302 METHODDEF(void)
303 start_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
304 {
305 gif_dest_ptr dest = (gif_dest_ptr) dinfo;
306
307 if (cinfo->quantize_colors)
308 emit_header(dest, cinfo->actual_number_of_colors, cinfo->colormap);
309 else
310 emit_header(dest, 256, (JSAMPARRAY) NULL);
311 }
312
313
314 /*
315 * Write some pixel data.
316 * In this module rows_supplied will always be 1.
317 */
318
319 METHODDEF(void)
320 put_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
321 JDIMENSION rows_supplied)
322 {
323 gif_dest_ptr dest = (gif_dest_ptr) dinfo;
324 register JSAMPROW ptr;
325 register JDIMENSION col;
326
327 ptr = dest->pub.buffer[0];
328 for (col = cinfo->output_width; col > 0; col--) {
329 compress_pixel(dest, GETJSAMPLE(*ptr++));
330 }
331 }
332
333
334 /*
335 * Finish up at the end of the file.
336 */
337
338 METHODDEF(void)
339 finish_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
340 {
341 gif_dest_ptr dest = (gif_dest_ptr) dinfo;
342
343 /* Flush "compression" mechanism */
344 compress_term(dest);
345 /* Write a zero-length data block to end the series */
346 putc(0, dest->pub.output_file);
347 /* Write the GIF terminator mark */
348 putc(';', dest->pub.output_file);
349 /* Make sure we wrote the output file OK */
350 fflush(dest->pub.output_file);
351 if (ferror(dest->pub.output_file))
352 ERREXIT(cinfo, JERR_FILE_WRITE);
353 }
354
355
356 /*
357 * The module selection routine for GIF format output.
358 */
359
360 GLOBAL(djpeg_dest_ptr)
361 jinit_write_gif (j_decompress_ptr cinfo)
362 {
363 gif_dest_ptr dest;
364
365 /* Create module interface object, fill in method pointers */
366 dest = (gif_dest_ptr)
367 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
368 SIZEOF(gif_dest_struct));
369 dest->cinfo = cinfo; /* make back link for subroutines */
370 dest->pub.start_output = start_output_gif;
371 dest->pub.put_pixel_rows = put_pixel_rows;
372 dest->pub.finish_output = finish_output_gif;
373
374 if (cinfo->out_color_space != JCS_GRAYSCALE &&
375 cinfo->out_color_space != JCS_RGB)
376 ERREXIT(cinfo, JERR_GIF_COLORSPACE);
377
378 /* Force quantization if color or if > 8 bits input */
379 if (cinfo->out_color_space != JCS_GRAYSCALE || cinfo->data_precision > 8) {
380 /* Force quantization to at most 256 colors */
381 cinfo->quantize_colors = TRUE;
382 if (cinfo->desired_number_of_colors > 256)
383 cinfo->desired_number_of_colors = 256;
384 }
385
386 /* Calculate output image dimensions so we can allocate space */
387 jpeg_calc_output_dimensions(cinfo);
388
389 if (cinfo->output_components != 1) /* safety check: just one component? */
390 ERREXIT(cinfo, JERR_GIF_BUG);
391
392 /* Create decompressor output buffer. */
393 dest->pub.buffer = (*cinfo->mem->alloc_sarray)
394 ((j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->output_width, (JDIMENSION) 1);
395 dest->pub.buffer_height = 1;
396
397 return &dest->pub;
398 }
399
400 #endif /* GIF_SUPPORTED */