PageRenderTime 82ms CodeModel.GetById 28ms app.highlight 48ms RepoModel.GetById 1ms app.codeStats 0ms

/src/FreeImage/Source/LibJPEG/wrgif.c

https://bitbucket.org/cabalistic/ogredeps/
C | 399 lines | 206 code | 62 blank | 131 comment | 32 complexity | c3358daa681a28d173c011180fa3323a MD5 | raw file
  1/*
  2 * wrgif.c
  3 *
  4 * Copyright (C) 1991-1997, Thomas G. Lane.
  5 * This file is part of the Independent JPEG Group's software.
  6 * For conditions of distribution and use, see the accompanying README file.
  7 *
  8 * This file contains routines to write output images in GIF format.
  9 *
 10 **************************************************************************
 11 * NOTE: to avoid entanglements with Unisys' patent on LZW compression,   *
 12 * this code has been modified to output "uncompressed GIF" files.        *
 13 * There is no trace of the LZW algorithm in this file.                   *
 14 **************************************************************************
 15 *
 16 * These routines may need modification for non-Unix environments or
 17 * specialized applications.  As they stand, they assume output to
 18 * an ordinary stdio stream.
 19 */
 20
 21/*
 22 * This code is loosely based on ppmtogif from the PBMPLUS distribution
 23 * of Feb. 1991.  That file contains the following copyright notice:
 24 *    Based on GIFENCODE by David Rowley <mgardi@watdscu.waterloo.edu>.
 25 *    Lempel-Ziv compression based on "compress" by Spencer W. Thomas et al.
 26 *    Copyright (C) 1989 by Jef Poskanzer.
 27 *    Permission to use, copy, modify, and distribute this software and its
 28 *    documentation for any purpose and without fee is hereby granted, provided
 29 *    that the above copyright notice appear in all copies and that both that
 30 *    copyright notice and this permission notice appear in supporting
 31 *    documentation.  This software is provided "as is" without express or
 32 *    implied warranty.
 33 *
 34 * We are also required to state that
 35 *    "The Graphics Interchange Format(c) is the Copyright property of
 36 *    CompuServe Incorporated. GIF(sm) is a Service Mark property of
 37 *    CompuServe Incorporated."
 38 */
 39
 40#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */
 41
 42#ifdef GIF_SUPPORTED
 43
 44
 45/* Private version of data destination object */
 46
 47typedef struct {
 48  struct djpeg_dest_struct pub;	/* public fields */
 49
 50  j_decompress_ptr cinfo;	/* back link saves passing separate parm */
 51
 52  /* State for packing variable-width codes into a bitstream */
 53  int n_bits;			/* current number of bits/code */
 54  int maxcode;			/* maximum code, given n_bits */
 55  INT32 cur_accum;		/* holds bits not yet output */
 56  int cur_bits;			/* # of bits in cur_accum */
 57
 58  /* State for GIF code assignment */
 59  int ClearCode;		/* clear code (doesn't change) */
 60  int EOFCode;			/* EOF code (ditto) */
 61  int code_counter;		/* counts output symbols */
 62
 63  /* GIF data packet construction buffer */
 64  int bytesinpkt;		/* # of bytes in current packet */
 65  char packetbuf[256];		/* workspace for accumulating packet */
 66
 67} gif_dest_struct;
 68
 69typedef gif_dest_struct * gif_dest_ptr;
 70
 71/* Largest value that will fit in N bits */
 72#define MAXCODE(n_bits)	((1 << (n_bits)) - 1)
 73
 74
 75/*
 76 * Routines to package finished data bytes into GIF data blocks.
 77 * A data block consists of a count byte (1..255) and that many data bytes.
 78 */
 79
 80LOCAL(void)
 81flush_packet (gif_dest_ptr dinfo)
 82/* flush any accumulated data */
 83{
 84  if (dinfo->bytesinpkt > 0) {	/* never write zero-length packet */
 85    dinfo->packetbuf[0] = (char) dinfo->bytesinpkt++;
 86    if (JFWRITE(dinfo->pub.output_file, dinfo->packetbuf, dinfo->bytesinpkt)
 87	!= (size_t) dinfo->bytesinpkt)
 88      ERREXIT(dinfo->cinfo, JERR_FILE_WRITE);
 89    dinfo->bytesinpkt = 0;
 90  }
 91}
 92
 93
 94/* Add a character to current packet; flush to disk if necessary */
 95#define CHAR_OUT(dinfo,c)  \
 96	{ (dinfo)->packetbuf[++(dinfo)->bytesinpkt] = (char) (c);  \
 97	    if ((dinfo)->bytesinpkt >= 255)  \
 98	      flush_packet(dinfo);  \
 99	}
100
101
102/* Routine to convert variable-width codes into a byte stream */
103
104LOCAL(void)
105output (gif_dest_ptr dinfo, int code)
106/* Emit a code of n_bits bits */
107/* Uses cur_accum and cur_bits to reblock into 8-bit bytes */
108{
109  dinfo->cur_accum |= ((INT32) code) << dinfo->cur_bits;
110  dinfo->cur_bits += dinfo->n_bits;
111
112  while (dinfo->cur_bits >= 8) {
113    CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
114    dinfo->cur_accum >>= 8;
115    dinfo->cur_bits -= 8;
116  }
117}
118
119
120/* The pseudo-compression algorithm.
121 *
122 * In this module we simply output each pixel value as a separate symbol;
123 * thus, no compression occurs.  In fact, there is expansion of one bit per
124 * pixel, because we use a symbol width one bit wider than the pixel width.
125 *
126 * GIF ordinarily uses variable-width symbols, and the decoder will expect
127 * to ratchet up the symbol width after a fixed number of symbols.
128 * To simplify the logic and keep the expansion penalty down, we emit a
129 * GIF Clear code to reset the decoder just before the width would ratchet up.
130 * Thus, all the symbols in the output file will have the same bit width.
131 * Note that emitting the Clear codes at the right times is a mere matter of
132 * counting output symbols and is in no way dependent on the LZW patent.
133 *
134 * With a small basic pixel width (low color count), Clear codes will be
135 * needed very frequently, causing the file to expand even more.  So this
136 * simplistic approach wouldn't work too well on bilevel images, for example.
137 * But for output of JPEG conversions the pixel width will usually be 8 bits
138 * (129 to 256 colors), so the overhead added by Clear symbols is only about
139 * one symbol in every 256.
140 */
141
142LOCAL(void)
143compress_init (gif_dest_ptr dinfo, int i_bits)
144/* Initialize pseudo-compressor */
145{
146  /* init all the state variables */
147  dinfo->n_bits = i_bits;
148  dinfo->maxcode = MAXCODE(dinfo->n_bits);
149  dinfo->ClearCode = (1 << (i_bits - 1));
150  dinfo->EOFCode = dinfo->ClearCode + 1;
151  dinfo->code_counter = dinfo->ClearCode + 2;
152  /* init output buffering vars */
153  dinfo->bytesinpkt = 0;
154  dinfo->cur_accum = 0;
155  dinfo->cur_bits = 0;
156  /* GIF specifies an initial Clear code */
157  output(dinfo, dinfo->ClearCode);
158}
159
160
161LOCAL(void)
162compress_pixel (gif_dest_ptr dinfo, int c)
163/* Accept and "compress" one pixel value.
164 * The given value must be less than n_bits wide.
165 */
166{
167  /* Output the given pixel value as a symbol. */
168  output(dinfo, c);
169  /* Issue Clear codes often enough to keep the reader from ratcheting up
170   * its symbol size.
171   */
172  if (dinfo->code_counter < dinfo->maxcode) {
173    dinfo->code_counter++;
174  } else {
175    output(dinfo, dinfo->ClearCode);
176    dinfo->code_counter = dinfo->ClearCode + 2;	/* reset the counter */
177  }
178}
179
180
181LOCAL(void)
182compress_term (gif_dest_ptr dinfo)
183/* Clean up at end */
184{
185  /* Send an EOF code */
186  output(dinfo, dinfo->EOFCode);
187  /* Flush the bit-packing buffer */
188  if (dinfo->cur_bits > 0) {
189    CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
190  }
191  /* Flush the packet buffer */
192  flush_packet(dinfo);
193}
194
195
196/* GIF header construction */
197
198
199LOCAL(void)
200put_word (gif_dest_ptr dinfo, unsigned int w)
201/* Emit a 16-bit word, LSB first */
202{
203  putc(w & 0xFF, dinfo->pub.output_file);
204  putc((w >> 8) & 0xFF, dinfo->pub.output_file);
205}
206
207
208LOCAL(void)
209put_3bytes (gif_dest_ptr dinfo, int val)
210/* Emit 3 copies of same byte value --- handy subr for colormap construction */
211{
212  putc(val, dinfo->pub.output_file);
213  putc(val, dinfo->pub.output_file);
214  putc(val, dinfo->pub.output_file);
215}
216
217
218LOCAL(void)
219emit_header (gif_dest_ptr dinfo, int num_colors, JSAMPARRAY colormap)
220/* Output the GIF file header, including color map */
221/* If colormap==NULL, synthesize a gray-scale colormap */
222{
223  int BitsPerPixel, ColorMapSize, InitCodeSize, FlagByte;
224  int cshift = dinfo->cinfo->data_precision - 8;
225  int i;
226
227  if (num_colors > 256)
228    ERREXIT1(dinfo->cinfo, JERR_TOO_MANY_COLORS, num_colors);
229  /* Compute bits/pixel and related values */
230  BitsPerPixel = 1;
231  while (num_colors > (1 << BitsPerPixel))
232    BitsPerPixel++;
233  ColorMapSize = 1 << BitsPerPixel;
234  if (BitsPerPixel <= 1)
235    InitCodeSize = 2;
236  else
237    InitCodeSize = BitsPerPixel;
238  /*
239   * Write the GIF header.
240   * Note that we generate a plain GIF87 header for maximum compatibility.
241   */
242  putc('G', dinfo->pub.output_file);
243  putc('I', dinfo->pub.output_file);
244  putc('F', dinfo->pub.output_file);
245  putc('8', dinfo->pub.output_file);
246  putc('7', dinfo->pub.output_file);
247  putc('a', dinfo->pub.output_file);
248  /* Write the Logical Screen Descriptor */
249  put_word(dinfo, (unsigned int) dinfo->cinfo->output_width);
250  put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
251  FlagByte = 0x80;		/* Yes, there is a global color table */
252  FlagByte |= (BitsPerPixel-1) << 4; /* color resolution */
253  FlagByte |= (BitsPerPixel-1);	/* size of global color table */
254  putc(FlagByte, dinfo->pub.output_file);
255  putc(0, dinfo->pub.output_file); /* Background color index */
256  putc(0, dinfo->pub.output_file); /* Reserved (aspect ratio in GIF89) */
257  /* Write the Global Color Map */
258  /* If the color map is more than 8 bits precision, */
259  /* we reduce it to 8 bits by shifting */
260  for (i=0; i < ColorMapSize; i++) {
261    if (i < num_colors) {
262      if (colormap != NULL) {
263	if (dinfo->cinfo->out_color_space == JCS_RGB) {
264	  /* Normal case: RGB color map */
265	  putc(GETJSAMPLE(colormap[0][i]) >> cshift, dinfo->pub.output_file);
266	  putc(GETJSAMPLE(colormap[1][i]) >> cshift, dinfo->pub.output_file);
267	  putc(GETJSAMPLE(colormap[2][i]) >> cshift, dinfo->pub.output_file);
268	} else {
269	  /* Grayscale "color map": possible if quantizing grayscale image */
270	  put_3bytes(dinfo, GETJSAMPLE(colormap[0][i]) >> cshift);
271	}
272      } else {
273	/* Create a gray-scale map of num_colors values, range 0..255 */
274	put_3bytes(dinfo, (i * 255 + (num_colors-1)/2) / (num_colors-1));
275      }
276    } else {
277      /* fill out the map to a power of 2 */
278      put_3bytes(dinfo, 0);
279    }
280  }
281  /* Write image separator and Image Descriptor */
282  putc(',', dinfo->pub.output_file); /* separator */
283  put_word(dinfo, 0);		/* left/top offset */
284  put_word(dinfo, 0);
285  put_word(dinfo, (unsigned int) dinfo->cinfo->output_width); /* image size */
286  put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
287  /* flag byte: not interlaced, no local color map */
288  putc(0x00, dinfo->pub.output_file);
289  /* Write Initial Code Size byte */
290  putc(InitCodeSize, dinfo->pub.output_file);
291
292  /* Initialize for "compression" of image data */
293  compress_init(dinfo, InitCodeSize+1);
294}
295
296
297/*
298 * Startup: write the file header.
299 */
300
301METHODDEF(void)
302start_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
303{
304  gif_dest_ptr dest = (gif_dest_ptr) dinfo;
305
306  if (cinfo->quantize_colors)
307    emit_header(dest, cinfo->actual_number_of_colors, cinfo->colormap);
308  else
309    emit_header(dest, 256, (JSAMPARRAY) NULL);
310}
311
312
313/*
314 * Write some pixel data.
315 * In this module rows_supplied will always be 1.
316 */
317
318METHODDEF(void)
319put_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
320		JDIMENSION rows_supplied)
321{
322  gif_dest_ptr dest = (gif_dest_ptr) dinfo;
323  register JSAMPROW ptr;
324  register JDIMENSION col;
325
326  ptr = dest->pub.buffer[0];
327  for (col = cinfo->output_width; col > 0; col--) {
328    compress_pixel(dest, GETJSAMPLE(*ptr++));
329  }
330}
331
332
333/*
334 * Finish up at the end of the file.
335 */
336
337METHODDEF(void)
338finish_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
339{
340  gif_dest_ptr dest = (gif_dest_ptr) dinfo;
341
342  /* Flush "compression" mechanism */
343  compress_term(dest);
344  /* Write a zero-length data block to end the series */
345  putc(0, dest->pub.output_file);
346  /* Write the GIF terminator mark */
347  putc(';', dest->pub.output_file);
348  /* Make sure we wrote the output file OK */
349  fflush(dest->pub.output_file);
350  if (ferror(dest->pub.output_file))
351    ERREXIT(cinfo, JERR_FILE_WRITE);
352}
353
354
355/*
356 * The module selection routine for GIF format output.
357 */
358
359GLOBAL(djpeg_dest_ptr)
360jinit_write_gif (j_decompress_ptr cinfo)
361{
362  gif_dest_ptr dest;
363
364  /* Create module interface object, fill in method pointers */
365  dest = (gif_dest_ptr)
366      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
367				  SIZEOF(gif_dest_struct));
368  dest->cinfo = cinfo;		/* make back link for subroutines */
369  dest->pub.start_output = start_output_gif;
370  dest->pub.put_pixel_rows = put_pixel_rows;
371  dest->pub.finish_output = finish_output_gif;
372
373  if (cinfo->out_color_space != JCS_GRAYSCALE &&
374      cinfo->out_color_space != JCS_RGB)
375    ERREXIT(cinfo, JERR_GIF_COLORSPACE);
376
377  /* Force quantization if color or if > 8 bits input */
378  if (cinfo->out_color_space != JCS_GRAYSCALE || cinfo->data_precision > 8) {
379    /* Force quantization to at most 256 colors */
380    cinfo->quantize_colors = TRUE;
381    if (cinfo->desired_number_of_colors > 256)
382      cinfo->desired_number_of_colors = 256;
383  }
384
385  /* Calculate output image dimensions so we can allocate space */
386  jpeg_calc_output_dimensions(cinfo);
387
388  if (cinfo->output_components != 1) /* safety check: just one component? */
389    ERREXIT(cinfo, JERR_GIF_BUG);
390
391  /* Create decompressor output buffer. */
392  dest->pub.buffer = (*cinfo->mem->alloc_sarray)
393    ((j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->output_width, (JDIMENSION) 1);
394  dest->pub.buffer_height = 1;
395
396  return (djpeg_dest_ptr) dest;
397}
398
399#endif /* GIF_SUPPORTED */