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Diffstat (limited to 'jpg/wrgif.c')
| -rw-r--r-- | jpg/wrgif.c | 399 |
1 files changed, 399 insertions, 0 deletions
diff --git a/jpg/wrgif.c b/jpg/wrgif.c new file mode 100644 index 0000000..5fe8328 --- /dev/null +++ b/jpg/wrgif.c @@ -0,0 +1,399 @@ +/* + * wrgif.c + * + * Copyright (C) 1991-1997, Thomas G. Lane. + * This file is part of the Independent JPEG Group's software. + * For conditions of distribution and use, see the accompanying README file. + * + * This file contains routines to write output images in GIF format. + * + ************************************************************************** + * NOTE: to avoid entanglements with Unisys' patent on LZW compression, * + * this code has been modified to output "uncompressed GIF" files. * + * There is no trace of the LZW algorithm in this file. * + ************************************************************************** + * + * These routines may need modification for non-Unix environments or + * specialized applications. As they stand, they assume output to + * an ordinary stdio stream. + */ + +/* + * This code is loosely based on ppmtogif from the PBMPLUS distribution + * of Feb. 1991. That file contains the following copyright notice: + * Based on GIFENCODE by David Rowley <mgardi@watdscu.waterloo.edu>. + * Lempel-Ziv compression based on "compress" by Spencer W. Thomas et al. + * Copyright (C) 1989 by Jef Poskanzer. + * Permission to use, copy, modify, and distribute this software and its + * documentation for any purpose and without fee is hereby granted, provided + * that the above copyright notice appear in all copies and that both that + * copyright notice and this permission notice appear in supporting + * documentation. This software is provided "as is" without express or + * implied warranty. + * + * We are also required to state that + * "The Graphics Interchange Format(c) is the Copyright property of + * CompuServe Incorporated. GIF(sm) is a Service Mark property of + * CompuServe Incorporated." + */ + +#include "cdjpeg.h" /* Common decls for cjpeg/djpeg applications */ + +#ifdef GIF_SUPPORTED + + +/* Private version of data destination object */ + +typedef struct { + struct djpeg_dest_struct pub; /* public fields */ + + j_decompress_ptr cinfo; /* back link saves passing separate parm */ + + /* State for packing variable-width codes into a bitstream */ + int n_bits; /* current number of bits/code */ + int maxcode; /* maximum code, given n_bits */ + INT32 cur_accum; /* holds bits not yet output */ + int cur_bits; /* # of bits in cur_accum */ + + /* State for GIF code assignment */ + int ClearCode; /* clear code (doesn't change) */ + int EOFCode; /* EOF code (ditto) */ + int code_counter; /* counts output symbols */ + + /* GIF data packet construction buffer */ + int bytesinpkt; /* # of bytes in current packet */ + char packetbuf[256]; /* workspace for accumulating packet */ + +} gif_dest_struct; + +typedef gif_dest_struct * gif_dest_ptr; + +/* Largest value that will fit in N bits */ +#define MAXCODE(n_bits) ((1 << (n_bits)) - 1) + + +/* + * Routines to package finished data bytes into GIF data blocks. + * A data block consists of a count byte (1..255) and that many data bytes. + */ + +LOCAL(void) +flush_packet (gif_dest_ptr dinfo) +/* flush any accumulated data */ +{ + if (dinfo->bytesinpkt > 0) { /* never write zero-length packet */ + dinfo->packetbuf[0] = (char) dinfo->bytesinpkt++; + if (JFWRITE(dinfo->pub.output_file, dinfo->packetbuf, dinfo->bytesinpkt) + != (size_t) dinfo->bytesinpkt) + ERREXIT(dinfo->cinfo, JERR_FILE_WRITE); + dinfo->bytesinpkt = 0; + } +} + + +/* Add a character to current packet; flush to disk if necessary */ +#define CHAR_OUT(dinfo,c) \ + { (dinfo)->packetbuf[++(dinfo)->bytesinpkt] = (char) (c); \ + if ((dinfo)->bytesinpkt >= 255) \ + flush_packet(dinfo); \ + } + + +/* Routine to convert variable-width codes into a byte stream */ + +LOCAL(void) +output (gif_dest_ptr dinfo, int code) +/* Emit a code of n_bits bits */ +/* Uses cur_accum and cur_bits to reblock into 8-bit bytes */ +{ + dinfo->cur_accum |= ((INT32) code) << dinfo->cur_bits; + dinfo->cur_bits += dinfo->n_bits; + + while (dinfo->cur_bits >= 8) { + CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF); + dinfo->cur_accum >>= 8; + dinfo->cur_bits -= 8; + } +} + + +/* The pseudo-compression algorithm. + * + * In this module we simply output each pixel value as a separate symbol; + * thus, no compression occurs. In fact, there is expansion of one bit per + * pixel, because we use a symbol width one bit wider than the pixel width. + * + * GIF ordinarily uses variable-width symbols, and the decoder will expect + * to ratchet up the symbol width after a fixed number of symbols. + * To simplify the logic and keep the expansion penalty down, we emit a + * GIF Clear code to reset the decoder just before the width would ratchet up. + * Thus, all the symbols in the output file will have the same bit width. + * Note that emitting the Clear codes at the right times is a mere matter of + * counting output symbols and is in no way dependent on the LZW patent. + * + * With a small basic pixel width (low color count), Clear codes will be + * needed very frequently, causing the file to expand even more. So this + * simplistic approach wouldn't work too well on bilevel images, for example. + * But for output of JPEG conversions the pixel width will usually be 8 bits + * (129 to 256 colors), so the overhead added by Clear symbols is only about + * one symbol in every 256. + */ + +LOCAL(void) +compress_init (gif_dest_ptr dinfo, int i_bits) +/* Initialize pseudo-compressor */ +{ + /* init all the state variables */ + dinfo->n_bits = i_bits; + dinfo->maxcode = MAXCODE(dinfo->n_bits); + dinfo->ClearCode = (1 << (i_bits - 1)); + dinfo->EOFCode = dinfo->ClearCode + 1; + dinfo->code_counter = dinfo->ClearCode + 2; + /* init output buffering vars */ + dinfo->bytesinpkt = 0; + dinfo->cur_accum = 0; + dinfo->cur_bits = 0; + /* GIF specifies an initial Clear code */ + output(dinfo, dinfo->ClearCode); +} + + +LOCAL(void) +compress_pixel (gif_dest_ptr dinfo, int c) +/* Accept and "compress" one pixel value. + * The given value must be less than n_bits wide. + */ +{ + /* Output the given pixel value as a symbol. */ + output(dinfo, c); + /* Issue Clear codes often enough to keep the reader from ratcheting up + * its symbol size. + */ + if (dinfo->code_counter < dinfo->maxcode) { + dinfo->code_counter++; + } else { + output(dinfo, dinfo->ClearCode); + dinfo->code_counter = dinfo->ClearCode + 2; /* reset the counter */ + } +} + + +LOCAL(void) +compress_term (gif_dest_ptr dinfo) +/* Clean up at end */ +{ + /* Send an EOF code */ + output(dinfo, dinfo->EOFCode); + /* Flush the bit-packing buffer */ + if (dinfo->cur_bits > 0) { + CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF); + } + /* Flush the packet buffer */ + flush_packet(dinfo); +} + + +/* GIF header construction */ + + +LOCAL(void) +put_word (gif_dest_ptr dinfo, unsigned int w) +/* Emit a 16-bit word, LSB first */ +{ + putc(w & 0xFF, dinfo->pub.output_file); + putc((w >> 8) & 0xFF, dinfo->pub.output_file); +} + + +LOCAL(void) +put_3bytes (gif_dest_ptr dinfo, int val) +/* Emit 3 copies of same byte value --- handy subr for colormap construction */ +{ + putc(val, dinfo->pub.output_file); + putc(val, dinfo->pub.output_file); + putc(val, dinfo->pub.output_file); +} + + +LOCAL(void) +emit_header (gif_dest_ptr dinfo, int num_colors, JSAMPARRAY colormap) +/* Output the GIF file header, including color map */ +/* If colormap==NULL, synthesize a gray-scale colormap */ +{ + int BitsPerPixel, ColorMapSize, InitCodeSize, FlagByte; + int cshift = dinfo->cinfo->data_precision - 8; + int i; + + if (num_colors > 256) + ERREXIT1(dinfo->cinfo, JERR_TOO_MANY_COLORS, num_colors); + /* Compute bits/pixel and related values */ + BitsPerPixel = 1; + while (num_colors > (1 << BitsPerPixel)) + BitsPerPixel++; + ColorMapSize = 1 << BitsPerPixel; + if (BitsPerPixel <= 1) + InitCodeSize = 2; + else + InitCodeSize = BitsPerPixel; + /* + * Write the GIF header. + * Note that we generate a plain GIF87 header for maximum compatibility. + */ + putc('G', dinfo->pub.output_file); + putc('I', dinfo->pub.output_file); + putc('F', dinfo->pub.output_file); + putc('8', dinfo->pub.output_file); + putc('7', dinfo->pub.output_file); + putc('a', dinfo->pub.output_file); + /* Write the Logical Screen Descriptor */ + put_word(dinfo, (unsigned int) dinfo->cinfo->output_width); + put_word(dinfo, (unsigned int) dinfo->cinfo->output_height); + FlagByte = 0x80; /* Yes, there is a global color table */ + FlagByte |= (BitsPerPixel-1) << 4; /* color resolution */ + FlagByte |= (BitsPerPixel-1); /* size of global color table */ + putc(FlagByte, dinfo->pub.output_file); + putc(0, dinfo->pub.output_file); /* Background color index */ + putc(0, dinfo->pub.output_file); /* Reserved (aspect ratio in GIF89) */ + /* Write the Global Color Map */ + /* If the color map is more than 8 bits precision, */ + /* we reduce it to 8 bits by shifting */ + for (i=0; i < ColorMapSize; i++) { + if (i < num_colors) { + if (colormap != NULL) { + if (dinfo->cinfo->out_color_space == JCS_RGB) { + /* Normal case: RGB color map */ + putc(GETJSAMPLE(colormap[0][i]) >> cshift, dinfo->pub.output_file); + putc(GETJSAMPLE(colormap[1][i]) >> cshift, dinfo->pub.output_file); + putc(GETJSAMPLE(colormap[2][i]) >> cshift, dinfo->pub.output_file); + } else { + /* Grayscale "color map": possible if quantizing grayscale image */ + put_3bytes(dinfo, GETJSAMPLE(colormap[0][i]) >> cshift); + } + } else { + /* Create a gray-scale map of num_colors values, range 0..255 */ + put_3bytes(dinfo, (i * 255 + (num_colors-1)/2) / (num_colors-1)); + } + } else { + /* fill out the map to a power of 2 */ + put_3bytes(dinfo, 0); + } + } + /* Write image separator and Image Descriptor */ + putc(',', dinfo->pub.output_file); /* separator */ + put_word(dinfo, 0); /* left/top offset */ + put_word(dinfo, 0); + put_word(dinfo, (unsigned int) dinfo->cinfo->output_width); /* image size */ + put_word(dinfo, (unsigned int) dinfo->cinfo->output_height); + /* flag byte: not interlaced, no local color map */ + putc(0x00, dinfo->pub.output_file); + /* Write Initial Code Size byte */ + putc(InitCodeSize, dinfo->pub.output_file); + + /* Initialize for "compression" of image data */ + compress_init(dinfo, InitCodeSize+1); +} + + +/* + * Startup: write the file header. + */ + +METHODDEF(void) +start_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo) +{ + gif_dest_ptr dest = (gif_dest_ptr) dinfo; + + if (cinfo->quantize_colors) + emit_header(dest, cinfo->actual_number_of_colors, cinfo->colormap); + else + emit_header(dest, 256, (JSAMPARRAY) NULL); +} + + +/* + * Write some pixel data. + * In this module rows_supplied will always be 1. + */ + +METHODDEF(void) +put_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo, + JDIMENSION rows_supplied) +{ + gif_dest_ptr dest = (gif_dest_ptr) dinfo; + register JSAMPROW ptr; + register JDIMENSION col; + + ptr = dest->pub.buffer[0]; + for (col = cinfo->output_width; col > 0; col--) { + compress_pixel(dest, GETJSAMPLE(*ptr++)); + } +} + + +/* + * Finish up at the end of the file. + */ + +METHODDEF(void) +finish_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo) +{ + gif_dest_ptr dest = (gif_dest_ptr) dinfo; + + /* Flush "compression" mechanism */ + compress_term(dest); + /* Write a zero-length data block to end the series */ + putc(0, dest->pub.output_file); + /* Write the GIF terminator mark */ + putc(';', dest->pub.output_file); + /* Make sure we wrote the output file OK */ + fflush(dest->pub.output_file); + if (ferror(dest->pub.output_file)) + ERREXIT(cinfo, JERR_FILE_WRITE); +} + + +/* + * The module selection routine for GIF format output. + */ + +GLOBAL(djpeg_dest_ptr) +jinit_write_gif (j_decompress_ptr cinfo) +{ + gif_dest_ptr dest; + + /* Create module interface object, fill in method pointers */ + dest = (gif_dest_ptr) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + SIZEOF(gif_dest_struct)); + dest->cinfo = cinfo; /* make back link for subroutines */ + dest->pub.start_output = start_output_gif; + dest->pub.put_pixel_rows = put_pixel_rows; + dest->pub.finish_output = finish_output_gif; + + if (cinfo->out_color_space != JCS_GRAYSCALE && + cinfo->out_color_space != JCS_RGB) + ERREXIT(cinfo, JERR_GIF_COLORSPACE); + + /* Force quantization if color or if > 8 bits input */ + if (cinfo->out_color_space != JCS_GRAYSCALE || cinfo->data_precision > 8) { + /* Force quantization to at most 256 colors */ + cinfo->quantize_colors = TRUE; + if (cinfo->desired_number_of_colors > 256) + cinfo->desired_number_of_colors = 256; + } + + /* Calculate output image dimensions so we can allocate space */ + jpeg_calc_output_dimensions(cinfo); + + if (cinfo->output_components != 1) /* safety check: just one component? */ + ERREXIT(cinfo, JERR_GIF_BUG); + + /* Create decompressor output buffer. */ + dest->pub.buffer = (*cinfo->mem->alloc_sarray) + ((j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->output_width, (JDIMENSION) 1); + dest->pub.buffer_height = 1; + + return (djpeg_dest_ptr) dest; +} + +#endif /* GIF_SUPPORTED */ |