/* * jrdgif.c * * Copyright (C) 1991, 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 read input images in GIF format. * * These routines may need modification for non-Unix environments or * specialized applications. As they stand, they assume input from * an ordinary stdio stream. They further assume that reading begins * at the start of the file; input_init may need work if the * user interface has already read some data (e.g., to determine that * the file is indeed GIF format). * * These routines are invoked via the methods get_input_row * and input_init/term. */ /* * This code is loosely based on giftoppm from the PBMPLUS distribution * of Feb. 1991. That file contains the following copyright notice: * +-------------------------------------------------------------------+ * | Copyright 1990, David Koblas. | * | 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 "jinclude.h" #ifdef GIF_SUPPORTED #define MAXCOLORMAPSIZE 256 /* max # of colors in a GIF colormap */ #define NUMCOLORS 3 /* # of colors */ #define CM_RED 0 /* color component numbers */ #define CM_GREEN 1 #define CM_BLUE 2 static JSAMPARRAY colormap; /* the colormap to use */ /* colormap[i][j] = value of i'th color component for pixel value j */ #define MAX_LZW_BITS 12 /* maximum LZW code size */ #define LZW_TABLE_SIZE (1< table of prefix symbols */ static UINT8 FAR *symbol_tail; /* => table of suffix bytes */ static UINT8 FAR *symbol_stack; /* stack for symbol expansions */ static UINT8 FAR *sp; /* stack pointer */ /* Static state for interlaced image processing */ static boolean is_interlaced; /* TRUE if have interlaced image */ static big_sarray_ptr interlaced_image; /* full image in interlaced order */ static long cur_row_number; /* need to know actual row number */ static long pass2_offset; /* # of pixel rows in pass 1 */ static long pass3_offset; /* # of pixel rows in passes 1&2 */ static long pass4_offset; /* # of pixel rows in passes 1,2,3 */ /* Forward declarations */ METHODDEF void load_interlaced_image PP((compress_info_ptr cinfo, JSAMPARRAY pixel_row)); METHODDEF void get_interlaced_row PP((compress_info_ptr cinfo, JSAMPARRAY pixel_row)); LOCAL int ReadByte (compress_info_ptr cinfo) /* Read next byte from GIF file */ { register FILE * infile = cinfo->input_file; int c; if ((c = getc(infile)) == EOF) ERREXIT(cinfo->emethods, "Premature EOF in GIF file"); return c; } LOCAL int GetDataBlock (compress_info_ptr cinfo, char *buf) /* Read a GIF data block, which has a leading count byte */ /* A zero-length block marks the end of a data block sequence */ { int count; count = ReadByte(cinfo); if (count > 0) { if (! ReadOK(cinfo->input_file, buf, count)) ERREXIT(cinfo->emethods, "Premature EOF in GIF file"); } return count; } LOCAL void SkipDataBlocks (compress_info_ptr cinfo) /* Skip a series of data blocks, until a block terminator is found */ { char buf[256]; while (GetDataBlock(cinfo, buf) > 0) /* skip */; } LOCAL void ReInitLZW (void) /* (Re)initialize LZW state; shared code for startup and Clear processing */ { code_size = input_code_size+1; limit_code = clear_code << 1; /* 2^code_size */ max_code = clear_code + 2; /* first unused code value */ sp = symbol_stack; /* init stack to empty */ } LOCAL void InitLZWCode (void) /* Initialize for a series of LZWReadByte (and hence GetCode) calls */ { /* GetCode initialization */ last_byte = 2; /* make safe to "recopy last two bytes" */ last_bit = 0; /* nothing in the buffer */ cur_bit = 0; /* force buffer load on first call */ out_of_blocks = FALSE; /* LZWReadByte initialization */ clear_code = 1 << input_code_size; /* compute special code values */ end_code = clear_code + 1; /* note that these do not change */ first_time = TRUE; ReInitLZW(); } LOCAL int GetCode (compress_info_ptr cinfo) /* Fetch the next code_size bits from the GIF data */ /* We assume code_size is less than 16 */ { register INT32 accum; int offs, ret, count; if ( (cur_bit+code_size) > last_bit) { /* Time to reload the buffer */ if (out_of_blocks) { TRACEMS(cinfo->emethods, 1, "Ran out of GIF bits"); return end_code; /* fake something useful */ } /* preserve last two bytes of what we have -- assume code_size <= 16 */ code_buf[0] = code_buf[last_byte-2]; code_buf[1] = code_buf[last_byte-1]; /* Load more bytes; set flag if we reach the terminator block */ if ((count = GetDataBlock(cinfo, &code_buf[2])) == 0) { out_of_blocks = TRUE; TRACEMS(cinfo->emethods, 1, "Ran out of GIF bits"); return end_code; /* fake something useful */ } /* Reset counters */ cur_bit = (cur_bit - last_bit) + 16; last_byte = 2 + count; last_bit = last_byte * 8; } /* Form up next 24 bits in accum */ offs = cur_bit >> 3; /* byte containing cur_bit */ #ifdef CHAR_IS_UNSIGNED accum = code_buf[offs+2]; accum <<= 8; accum |= code_buf[offs+1]; accum <<= 8; accum |= code_buf[offs]; #else accum = code_buf[offs+2] & 0xFF; accum <<= 8; accum |= code_buf[offs+1] & 0xFF; accum <<= 8; accum |= code_buf[offs] & 0xFF; #endif /* Right-align cur_bit in accum, then mask off desired number of bits */ accum >>= (cur_bit & 7); ret = ((int) accum) & ((1 << code_size) - 1); cur_bit += code_size; return ret; } LOCAL int LZWReadByte (compress_info_ptr cinfo) /* Read an LZW-compressed byte */ { static int oldcode; /* previous LZW symbol */ static int firstcode; /* first byte of oldcode's expansion */ register int code; /* current working code */ int incode; /* saves actual input code */ /* First time, just eat the expected Clear code(s) and return next code, */ /* which is assumed to be a raw byte. */ if (first_time) { first_time = FALSE; do { code = GetCode(cinfo); } while (code == clear_code); firstcode = oldcode = code; /* make firstcode, oldcode valid! */ return code; } /* If any codes are stacked from a previously read symbol, return them */ if (sp > symbol_stack) return (int) *(--sp); code = GetCode(cinfo); if (code == clear_code) { /* Reinit static state, swallow any extra Clear codes, and return */ ReInitLZW(); do { code = GetCode(cinfo); } while (code == clear_code); firstcode = oldcode = code; /* gotta reinit these too */ return code; } if (code == end_code) { /* Skip the rest of the image, unless GetCode already read terminator */ if (! out_of_blocks) SkipDataBlocks(cinfo); return -1; } /* Normal raw byte or LZW symbol */ incode = code; /* save for a moment */ if (code >= max_code) { /* special case for not-yet-defined symbol */ *sp++ = (UINT8) firstcode; /* it will be defined as oldcode/firstcode */ code = oldcode; } /* If it's a symbol, expand it into the stack */ while (code >= clear_code) { *sp++ = symbol_tail[code]; /* tail of symbol: a simple byte value */ code = symbol_head[code]; /* head of symbol: another LZW symbol */ } /* At this point code just represents a raw byte */ firstcode = code; /* save for possible future use */ /* If there's room in table, */ if ((code = max_code) < LZW_TABLE_SIZE) { /* Define a new symbol = prev sym + head of this sym's expansion */ symbol_head[code] = oldcode; symbol_tail[code] = (UINT8) firstcode; max_code++; /* Is it time to increase code_size? */ if ((max_code >= limit_code) && (code_size < MAX_LZW_BITS)) { code_size++; limit_code <<= 1; /* keep equal to 2^code_size */ } } oldcode = incode; /* save last input symbol for future use */ return firstcode; /* return first byte of symbol's expansion */ } LOCAL void ReadColorMap (compress_info_ptr cinfo, int cmaplen, JSAMPARRAY cmap) /* Read a GIF colormap */ { int i; for (i = 0; i < cmaplen; i++) { cmap[CM_RED][i] = (JSAMPLE) ReadByte(cinfo); cmap[CM_GREEN][i] = (JSAMPLE) ReadByte(cinfo); cmap[CM_BLUE][i] = (JSAMPLE) ReadByte(cinfo); } } LOCAL void DoExtension (compress_info_ptr cinfo) /* Process an extension block */ /* Currently we ignore 'em all */ { int extlabel; /* Read extension label byte */ extlabel = ReadByte(cinfo); TRACEMS1(cinfo->emethods, 1, "Ignoring GIF extension block of type 0x%02x", extlabel); /* Skip the data block(s) associated with the extension */ SkipDataBlocks(cinfo); } /* * Read the file header; return image size and component count. */ METHODDEF void input_init (compress_info_ptr cinfo) { char hdrbuf[10]; /* workspace for reading control blocks */ UINT16 width, height; /* image dimensions */ int colormaplen, aspectRatio; int c; /* Allocate space to store the colormap */ colormap = (*cinfo->emethods->alloc_small_sarray) ((long) MAXCOLORMAPSIZE, (long) NUMCOLORS); /* Read and verify GIF Header */ if (! ReadOK(cinfo->input_file, hdrbuf, 6)) ERREXIT(cinfo->emethods, "Not a GIF file"); if (strncmp(hdrbuf, "GIF", 3) != 0) ERREXIT(cinfo->emethods, "Not a GIF file"); /* Check for expected version numbers. * If unknown version, give warning and try to process anyway; * this is per recommendation in GIF89a standard. */ if ((strncmp(hdrbuf+3, "87a", 3) != 0) && (strncmp(hdrbuf+3, "89a", 3) != 0)) TRACEMS3(cinfo->emethods, 1, "Warning: unexpected GIF version number '%c%c%c'", hdrbuf[3], hdrbuf[4], hdrbuf[5]); /* Read and decipher Logical Screen Descriptor */ if (! ReadOK(cinfo->input_file, hdrbuf, 7)) ERREXIT(cinfo->emethods, "Premature EOF in GIF file"); width = LM_to_uint(hdrbuf[0],hdrbuf[1]); height = LM_to_uint(hdrbuf[2],hdrbuf[3]); colormaplen = 2 << (hdrbuf[4] & 0x07); /* we ignore the color resolution, sort flag, and background color index */ aspectRatio = hdrbuf[6] & 0xFF; if (aspectRatio != 0 && aspectRatio != 49) TRACEMS(cinfo->emethods, 1, "Warning: nonsquare pixels in input"); /* Read global colormap if header indicates it is present */ if (BitSet(hdrbuf[4], COLORMAPFLAG)) ReadColorMap(cinfo, colormaplen, colormap); /* Scan until we reach start of desired image. * We don't currently support skipping images, but could add it easily. */ for (;;) { c = ReadByte(cinfo); if (c == ';') /* GIF terminator?? */ ERREXIT(cinfo->emethods, "Too few images in GIF file"); if (c == '!') { /* Extension */ DoExtension(cinfo); continue; } if (c != ',') { /* Not an image separator? */ TRACEMS1(cinfo->emethods, 1, "Bogus input char 0x%02x, ignoring", c); continue; } /* Read and decipher Local Image Descriptor */ if (! ReadOK(cinfo->input_file, hdrbuf, 9)) ERREXIT(cinfo->emethods, "Premature EOF in GIF file"); /* we ignore top/left position info, also sort flag */ width = LM_to_uint(hdrbuf[4],hdrbuf[5]); height = LM_to_uint(hdrbuf[6],hdrbuf[7]); is_interlaced = BitSet(hdrbuf[8], INTERLACE); colormaplen = 2 << (hdrbuf[8] & 0x07); /* Read local colormap if header indicates it is present */ /* Note: if we wanted to support skipping images, */ /* we'd need to skip rather than read colormap for ignored images */ if (BitSet(hdrbuf[8], COLORMAPFLAG)) ReadColorMap(cinfo, colormaplen, colormap); input_code_size = ReadByte(cinfo); /* get minimum-code-size byte */ if (input_code_size < 2 || input_code_size >= MAX_LZW_BITS) ERREXIT1(cinfo->emethods, "Bogus codesize %d", input_code_size); /* Reached desired image, so break out of loop */ /* If we wanted to skip this image, */ /* we'd call SkipDataBlocks and then continue the loop */ break; } /* Prepare to read selected image: first initialize LZW decompressor */ symbol_head = (UINT16 FAR *) (*cinfo->emethods->alloc_medium) (LZW_TABLE_SIZE * SIZEOF(UINT16)); symbol_tail = (UINT8 FAR *) (*cinfo->emethods->alloc_medium) (LZW_TABLE_SIZE * SIZEOF(UINT8)); symbol_stack = (UINT8 FAR *) (*cinfo->emethods->alloc_medium) (LZW_TABLE_SIZE * SIZEOF(UINT8)); InitLZWCode(); /* * If image is interlaced, we read it into a full-size sample array, * decompressing as we go; then get_input_row selects rows from the * sample array in the proper order. */ if (is_interlaced) { /* We request the big array now, but can't access it until the pipeline * controller causes all the big arrays to be allocated. Hence, the * actual work of reading the image is postponed until the first call * of get_input_row. */ interlaced_image = (*cinfo->emethods->request_big_sarray) ((long) width, (long) height, 1L); cinfo->methods->get_input_row = load_interlaced_image; } /* Return info about the image. */ cinfo->input_components = NUMCOLORS; cinfo->in_color_space = CS_RGB; cinfo->image_width = width; cinfo->image_height = height; cinfo->data_precision = 8; } /* * Read one row of pixels. * This version is used for noninterlaced GIF images: * we read directly from the GIF file. */ METHODDEF void get_input_row (compress_info_ptr cinfo, JSAMPARRAY pixel_row) { register JSAMPROW ptr0, ptr1, ptr2; register long col; register int c; ptr0 = pixel_row[0]; ptr1 = pixel_row[1]; ptr2 = pixel_row[2]; for (col = cinfo->image_width; col > 0; col--) { if ((c = LZWReadByte(cinfo)) < 0) ERREXIT(cinfo->emethods, "Premature end of GIF image"); *ptr0++ = colormap[CM_RED][c]; *ptr1++ = colormap[CM_GREEN][c]; *ptr2++ = colormap[CM_BLUE][c]; } } /* * Read one row of pixels. * This version is used for the first call on get_input_row when * reading an interlaced GIF file: we read the whole image into memory. */ METHODDEF void load_interlaced_image (compress_info_ptr cinfo, JSAMPARRAY pixel_row) { JSAMPARRAY image_ptr; register JSAMPROW sptr; register long col; register int c; long row; /* Read the interlaced image into the big array we've created. */ for (row = 0; row < cinfo->image_height; row++) { image_ptr = (*cinfo->emethods->access_big_sarray) (interlaced_image, row, TRUE); sptr = image_ptr[0]; for (col = cinfo->image_width; col > 0; col--) { if ((c = LZWReadByte(cinfo)) < 0) ERREXIT(cinfo->emethods, "Premature end of GIF image"); *sptr++ = (JSAMPLE) c; } } /* Replace method pointer so subsequent calls don't come here. */ cinfo->methods->get_input_row = get_interlaced_row; /* Initialize for get_interlaced_row, and perform first call on it. */ cur_row_number = 0; pass2_offset = (cinfo->image_height + 7L) / 8L; pass3_offset = pass2_offset + (cinfo->image_height + 3L) / 8L; pass4_offset = pass3_offset + (cinfo->image_height + 1L) / 4L; get_interlaced_row(cinfo, pixel_row); } /* * Read one row of pixels. * This version is used for interlaced GIF images: * we read from the big in-memory image. */ METHODDEF void get_interlaced_row (compress_info_ptr cinfo, JSAMPARRAY pixel_row) { JSAMPARRAY image_ptr; register JSAMPROW sptr, ptr0, ptr1, ptr2; register long col; register int c; long irow; /* Figure out which row of interlaced image is needed, and access it. */ switch ((int) (cur_row_number & 7L)) { case 0: /* first-pass row */ irow = cur_row_number >> 3; break; case 4: /* second-pass row */ irow = (cur_row_number >> 3) + pass2_offset; break; case 2: /* third-pass row */ case 6: irow = (cur_row_number >> 2) + pass3_offset; break; default: /* fourth-pass row */ irow = (cur_row_number >> 1) + pass4_offset; break; } image_ptr = (*cinfo->emethods->access_big_sarray) (interlaced_image, irow, FALSE); /* Scan the row, expand colormap, and output */ sptr = image_ptr[0]; ptr0 = pixel_row[0]; ptr1 = pixel_row[1]; ptr2 = pixel_row[2]; for (col = cinfo->image_width; col > 0; col--) { c = GETJSAMPLE(*sptr++); *ptr0++ = colormap[CM_RED][c]; *ptr1++ = colormap[CM_GREEN][c]; *ptr2++ = colormap[CM_BLUE][c]; } cur_row_number++; /* for next time */ } /* * Finish up at the end of the file. */ METHODDEF void input_term (compress_info_ptr cinfo) { if (is_interlaced) { (*cinfo->emethods->free_big_sarray) (interlaced_image); } (*cinfo->emethods->free_small_sarray) (colormap, (long) NUMCOLORS); (*cinfo->emethods->free_medium) ((void FAR *) symbol_head); (*cinfo->emethods->free_medium) ((void FAR *) symbol_tail); (*cinfo->emethods->free_medium) ((void FAR *) symbol_stack); } /* * The method selection routine for GIF format input. * Note that this must be called by the user interface before calling * jpeg_compress. If multiple input formats are supported, the * user interface is responsible for discovering the file format and * calling the appropriate method selection routine. */ GLOBAL void jselrgif (compress_info_ptr cinfo) { cinfo->methods->input_init = input_init; cinfo->methods->get_input_row = get_input_row; /* assume uninterlaced */ cinfo->methods->input_term = input_term; } #endif /* GIF_SUPPORTED */