/* +-------------------------------------------------------------------+ */ /* | Copyright 1990, 1991, 1993, David Koblas. (koblas@netcom.com) | */ /* | 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. | */ /* +-------------------------------------------------------------------+ */ /* There is a copy of the GIF89 specification, as defined by its inventor, Compuserve, in 1989, at http://members.aol.com/royalef/gif89a.txt This covers the high level format, but does not cover how the "data" contents of a GIF image represent the raster of color table indices. An appendix describes extensions to Lempel-Ziv that GIF makes (variable length compression codes and the clear and end codes), but does not describe the Lempel-Ziv base. */ #define _BSD_SOURCE /* Make sure strcasecmp() is in string.h */ #include #include #include "pm_c_util.h" #include "mallocvar.h" #include "nstring.h" #include "shhopt.h" #include "pnm.h" #define GIFMAXVAL 255 #define MAXCOLORMAPSIZE 256 #define CM_RED 0 #define CM_GRN 1 #define CM_BLU 2 #define MAX_LZW_BITS 12 #define INTERLACE 0x40 #define LOCALCOLORMAP 0x80 #define BitSet(byte, bit) (((byte) & (bit)) == (bit)) #if !defined(BYTE_ORDER) || !defined(LITTLE_ENDIAN) /* make sure (BYTE_ORDER == LITTLE_ENDIAN) is FALSE */ #define BYTE_ORDER 0 #define LITTLE_ENDIAN 1 #endif static __inline__ bool ReadOK(FILE * const fileP, unsigned char * const buffer, size_t const len) { size_t bytesRead; bytesRead = fread(buffer, len, 1, fileP); return (bytesRead != 0); } static void readFile(FILE * const ifP, unsigned char * const buffer, size_t const len, const char ** const errorP) { size_t bytesRead; bytesRead = fread(buffer, len, 1, ifP); if (bytesRead == len) *errorP = NULL; else { if (ferror(ifP)) asprintfN(errorP, "Error reading file. errno=%d (%s)", errno, strerror(errno)); else if (feof(ifP)) asprintfN(errorP, "End of file encountered"); else asprintfN(errorP, "Short read -- %u bytes of %u", (unsigned)bytesRead, (unsigned)len); } } #define LM_to_uint(a,b) (((b)<<8)|(a)) static int const maxnum_lzwCode = (1<verbose, 0); OPTENT3(0, "comments", OPT_FLAG, NULL, &cmdlineP->comments, 0); OPTENT3(0, "quitearly", OPT_FLAG, NULL, &cmdlineP->quitearly, 0); OPTENT3(0, "repair", OPT_FLAG, NULL, &cmdlineP->repair, 0); OPTENT3(0, "image", OPT_STRING, &image, &imageSpec, 0); OPTENT3(0, "alphaout", OPT_STRING, &cmdlineP->alpha_filename, &alphaSpec, 0); opt.opt_table = option_def; opt.short_allowed = FALSE; /* We have no short (old-fashioned) options */ opt.allowNegNum = FALSE; /* We have no parms that are negative numbers */ optParseOptions3( &argc, argv, opt, sizeof(opt), 0); /* Uses and sets argc, argv, and some of *cmdlineP and others. */ if (!imageSpec) { cmdlineP->image_no = 0; cmdlineP->all_images = FALSE; } else { if (strcasecmp(image, "all") == 0) cmdlineP->all_images = TRUE; else { char * tailptr; long const imageNo = strtol(image, &tailptr, 10); if (*tailptr != '\0') pm_error("Invalid value for '-image' option. Must be either " "a number or 'all'. You specified '%s'", image); else if (imageNo < 0) pm_error("Invalid value for '-image' option. Must be " "positive. You specified %ld", imageNo); else if (imageNo == 0) pm_error("Invalid value for 'image' option. You specified " "zero. The first image is 1."); cmdlineP->all_images = FALSE; cmdlineP->image_no = (unsigned int) imageNo - 1; } } if (argc-1 == 0) cmdlineP->input_filespec = "-"; else if (argc-1 != 1) pm_error("Program takes zero or one argument (filename). You " "specified %d", argc-1); else cmdlineP->input_filespec = argv[1]; if (!alphaSpec) cmdlineP->alpha_filename = NULL; } typedef unsigned char gifColorMap[3][MAXCOLORMAPSIZE]; struct gifScreen { unsigned int Width; unsigned int Height; gifColorMap ColorMap; unsigned int ColorMapSize; /* Number of colors in the color map. */ unsigned int ColorResolution; unsigned int Background; unsigned int AspectRatio; /* Aspect ratio of each pixel, times 64, minus 15. (i.e. 1 => 1:4). But Zero means 1:1. */ int hasGray; /* Boolean: global colormap has at least one gray color (not counting black and white) */ int hasColor; /* Boolean: global colormap has at least one non-gray, non-black, non-white color */ }; struct gif89 { int transparent; int delayTime; int inputFlag; int disposal; }; static void initGif89(struct gif89 * const gif89P) { gif89P->transparent = -1; gif89P->delayTime = -1; gif89P->inputFlag = -1; gif89P->disposal = -1; } static int verbose; int showComment; static void readColorMap(FILE *ifP, const int colormapsize, unsigned char colormap[3][MAXCOLORMAPSIZE], int *hasGrayP, int * const hasColorP) { int i; unsigned char rgb[3]; assert(colormapsize <= MAXCOLORMAPSIZE); *hasGrayP = FALSE; /* initial assumption */ *hasColorP = FALSE; /* initial assumption */ for (i = 0; i < colormapsize; ++i) { if (! ReadOK(ifP, rgb, sizeof(rgb))) pm_error("Unable to read Color %d from colormap", i); colormap[CM_RED][i] = rgb[0] ; colormap[CM_GRN][i] = rgb[1] ; colormap[CM_BLU][i] = rgb[2] ; if (rgb[0] == rgb[1] && rgb[1] == rgb[2]) { if (rgb[0] != 0 && rgb[0] != GIFMAXVAL) *hasGrayP = TRUE; } else *hasColorP = TRUE; } } static bool zeroDataBlock = FALSE; /* the most recently read DataBlock was an EOD marker, i.e. had zero length */ static void getDataBlock(FILE * const ifP, unsigned char * const buf, bool * const eofP, unsigned int * const lengthP, const char ** const errorP) { /*---------------------------------------------------------------------------- Read a DataBlock from file 'ifP', return it at 'buf'. The first byte of the datablock is the length, in pure binary, of the rest of the datablock. We return the data portion (not the length byte) of the datablock at 'buf', and its length as *lengthP. Except that if we hit EOF or have an I/O error reading the first byte (size field) of the DataBlock, we return *eofP == TRUE and *lengthP == 0. We return *eofP == FALSE if we don't hit EOF or have an I/O error. If we hit EOF or have an I/O error reading the data portion of the DataBlock, we exit the program with pm_error(). -----------------------------------------------------------------------------*/ unsigned char count; bool successfulRead; long const pos = ftell(ifP); successfulRead = ReadOK(ifP, &count, 1); if (!successfulRead) { pm_message("EOF or error in reading DataBlock size from file" ); *errorP = FALSE; *eofP = TRUE; *lengthP = 0; } else { if (verbose) pm_message("%d byte block at Position %ld", count, pos); *eofP = FALSE; *lengthP = count; if (count == 0) { *errorP = NULL; zeroDataBlock = TRUE; } else { bool successfulRead; zeroDataBlock = FALSE; successfulRead = ReadOK(ifP, buf, count); if (successfulRead) *errorP = NULL; else asprintfN(errorP, "EOF or error reading data portion of %u byte " "DataBlock from file", count); } } } static void readThroughEod(FILE * const ifP) { /*---------------------------------------------------------------------------- Read the file 'ifP' through the next EOD marker. An EOD marker is a a zero length data block. If there is no EOD marker between the present file position and EOF, we read to EOF and issue warning message about a missing EOD marker. -----------------------------------------------------------------------------*/ unsigned char buf[260]; bool eod; eod = FALSE; /* initial value */ while (!eod) { bool eof; unsigned int count; const char * error; getDataBlock(ifP, buf, &eof, &count, &error); if (error || eof) pm_message("EOF encountered before EOD marker. The GIF " "file is malformed, but we are proceeding " "anyway as if an EOD marker were at the end " "of the file."); if (error || eof || count == 0) eod = TRUE; } } static void doCommentExtension(FILE * const ifP) { /*---------------------------------------------------------------------------- Read the rest of a comment extension from the input file 'ifP' and handle it. We ought to deal with the possibility that the comment is not text. I.e. it could have nonprintable characters or embedded nulls. I don't know if the GIF spec requires regular text or not. -----------------------------------------------------------------------------*/ char buf[255+1]; unsigned int blocklen; bool done; done = FALSE; while (!done) { bool eof; const char * error; getDataBlock(ifP, (unsigned char*) buf, &eof, &blocklen, &error); if (error) pm_error("Error reading a data block in a comment extension. %s", error); if (blocklen == 0 || eof) done = TRUE; else { buf[blocklen] = '\0'; if (showComment) { pm_message("gif comment: %s", buf); } } } } static void doGraphicControlExtension(FILE * const ifP, struct gif89 * const gif89P) { bool eof; unsigned int length; static unsigned char buf[256]; const char * error; getDataBlock(ifP, buf, &eof, &length, &error); if (error) pm_error("Error reading 1st data block of Graphic Control Extension"); if (eof) pm_error("EOF/error encountered reading " "1st DataBlock of Graphic Control Extension."); else if (length < 4) pm_error("graphic control extension 1st DataBlock too short. " "It must be at least 4 bytes; it is %d bytes.", length); else { gif89P->disposal = (buf[0] >> 2) & 0x7; gif89P->inputFlag = (buf[0] >> 1) & 0x1; gif89P->delayTime = LM_to_uint(buf[1],buf[2]); if ((buf[0] & 0x1) != 0) gif89P->transparent = buf[3]; readThroughEod(ifP); } } static void doExtension(FILE * const ifP, int const label, struct gif89 * const gif89P) { const char * str; switch (label) { case 0x01: /* Plain Text Extension */ str = "Plain Text"; #ifdef notdef GetDataBlock(ifP, (unsigned char*) buf, &eof, &length); lpos = LM_to_uint(buf[0], buf[1]); tpos = LM_to_uint(buf[2], buf[3]); width = LM_to_uint(buf[4], buf[5]); height = LM_to_uint(buf[6], buf[7]); cellw = buf[8]; cellh = buf[9]; foreground = buf[10]; background = buf[11]; while (GetDataBlock(ifP, (unsigned char*) buf) != 0) { PPM_ASSIGN(xels[ypos][xpos], cmap[CM_RED][v], cmap[CM_GRN][v], cmap[CM_BLU][v]); ++index; } #else readThroughEod(ifP); #endif break; case 0xff: /* Application Extension */ str = "Application"; readThroughEod(ifP); break; case 0xfe: /* Comment Extension */ str = "Comment"; doCommentExtension(ifP); break; case 0xf9: /* Graphic Control Extension */ str = "Graphic Control"; doGraphicControlExtension(ifP, gif89P); break; default: { static char buf[256]; str = buf; sprintf(buf, "UNKNOWN (0x%02x)", label); pm_message("Ignoring unrecognized extension (type 0x%02x)", label); readThroughEod(ifP); } break; } if (verbose) pm_message(" got a '%s' extension", str ); } struct getCodeState { unsigned char buf[280]; /* This is the buffer through which we read the data from the stream. We must buffer it because we have to read whole data blocks at a time, but our client wants one code at a time. The buffer typically contains the contents of one data block plus two bytes from the previous data block. */ int bufCount; /* This is the number of bytes of contents in buf[]. */ int curbit; /* The bit number (starting at 0) within buf[] of the next bit to be returned. If the next bit to be returned is not yet in buf[] (we've already returned everything in there), this points one beyond the end of the buffer contents. */ bool streamExhausted; /* The last time we read from the input stream, we got an EOD marker or EOF or an error that prevents further reading of the stream. */ }; static void getAnotherBlock(FILE * const ifP, struct getCodeState * const gsP, const char ** const errorP) { unsigned int count; unsigned int assumed_count; bool eof; /* Shift buffer down so last two bytes are now the first two bytes. Shift 'curbit' cursor, which must be somewhere in or immediately after those two bytes, accordingly. */ gsP->buf[0] = gsP->buf[gsP->bufCount-2]; gsP->buf[1] = gsP->buf[gsP->bufCount-1]; gsP->curbit -= (gsP->bufCount-2)*8; gsP->bufCount = 2; /* Add the next block to the buffer */ getDataBlock(ifP, &gsP->buf[gsP->bufCount], &eof, &count, errorP); if (*errorP) gsP->streamExhausted = TRUE; else { if (eof) { pm_message("EOF encountered in image " "before EOD marker. The GIF " "file is malformed, but we are proceeding " "anyway as if an EOD marker were at the end " "of the file."); assumed_count = 0; } else assumed_count = count; gsP->streamExhausted = (assumed_count == 0); gsP->bufCount += assumed_count; } } static struct getCodeState getCodeState; static void getCode_init(struct getCodeState * const getCodeStateP) { /* Fake a previous data block */ getCodeStateP->buf[0] = 0; getCodeStateP->buf[1] = 0; getCodeStateP->bufCount = 2; getCodeStateP->curbit = getCodeStateP->bufCount * 8; getCodeStateP->streamExhausted = FALSE; } static unsigned int bitsOfLeBuffer(const unsigned char * const buf, unsigned int const start, unsigned int const len) { /*---------------------------------------------------------------------------- Return a string of 'len' bits (up to 16) starting at bit 'start' of buffer buf[]. In the buffer, the bits are numbered Intel-style, with the first bit of a byte being the least significant bit. So bit 3 is the "16" bit of the first byte of buf[]. We return the string as an integer such that its pure binary encoding with the bits numbered Intel-style is the string. E.g. the string 0,1,1 yields six. -----------------------------------------------------------------------------*/ uint32_t codeBlock; /* The 3 whole bytes of the buffer that contain the requested bit string */ assert(len <= 16); if (BYTE_ORDER == LITTLE_ENDIAN) /* Fast path */ codeBlock = *(uint32_t *) & buf[start/8]; else /* logic works for little endian too */ codeBlock = (buf[start/8+0] << 0) | (buf[start/8+1] << 8) | (buf[start/8+2] << 16); return (unsigned int) (codeBlock >> (start % 8)) & ((1 << len) - 1); } static void getCode_get(struct getCodeState * const gsP, FILE * const ifP, int const codeSize, bool * const eofP, unsigned int * const codeP, const char ** const errorP) { /*---------------------------------------------------------------------------- Read and return the next lzw code from the file *ifP. 'codeSize' is the number of bits in the code we are to get. Return *eofP == TRUE iff we hit the end of the stream. That means a legal end of stream, marked by an EOD marker, not just end of file. An end of file in the middle of the GIF stream is an error. If there are bits left in the stream, but not 'codeSize' of them, we call that a success with *eofP == TRUE. Return the code read (assuming *eofP == FALSE and *errorP == NULL) as *codeP. -----------------------------------------------------------------------------*/ *errorP = NULL; while (gsP->curbit + codeSize > gsP->bufCount * 8 && !gsP->streamExhausted && !*errorP) /* Not enough left in buffer to satisfy request. Get the next data block into the buffer. Note that a data block may be as small as one byte, so we may need to do this multiple times to get the full code. (This probably never happens in practice). */ getAnotherBlock(ifP, gsP, errorP); if (!*errorP) { if (gsP->curbit + codeSize > gsP->bufCount * 8) { /* The buffer still doesn't have enough bits in it; that means there were no data blocks left to read. */ *eofP = TRUE; { int const bitsUnused = gsP->bufCount * 8 - gsP->curbit; if (bitsUnused > 0) pm_message("Stream ends with a partial code " "(%d bits left in file; " "expected a %d bit code). Ignoring.", bitsUnused, codeSize); } } else { *codeP = bitsOfLeBuffer(gsP->buf, gsP->curbit, codeSize); gsP->curbit += codeSize; *eofP = FALSE; } } } struct stack { /* Stack grows from low addresses to high addresses */ int * stack; /* malloc'ed array */ int * sp; /* stack pointer */ int * top; /* next word above top of stack */ }; static void initStack(struct stack * const stackP, unsigned int const size) { MALLOCARRAY(stackP->stack, size); if (stackP->stack == NULL) pm_error("Unable to allocate %d-word stack.", size); stackP->sp = stackP->stack; stackP->top = stackP->stack + size; } static void pushStack(struct stack * const stackP, int const value) { if (stackP->sp >= stackP->top) pm_error("stack overflow"); *(stackP->sp++) = value; } static bool stackIsEmpty(const struct stack * const stackP) { return stackP->sp == stackP->stack; } static int popStack(struct stack * const stackP) { if (stackP->sp <= stackP->stack) pm_error("stack underflow"); return *(--stackP->sp); } static void termStack(struct stack * const stackP) { free(stackP->stack); stackP->stack = NULL; } /*---------------------------------------------------------------------------- Some notes on LZW. LZW is an extension of Limpel-Ziv. The two extensions are: 1) in Limpel-Ziv, codes are all the same number of bits. In LZW, they start out small and increase as the stream progresses. 2) LZW has a clear code that resets the string table and code size. The LZW code space is allocated as follows: The true data elements are dataWidth bits wide, so the maximum value of a true data element is 2**dataWidth-1. We call that max_dataVal. The first byte in the stream tells you what dataWidth is. LZW codes 0 - max_dataVal are direct codes. Each one represents the true data element whose value is that of the LZW code itself. No decompression is required. max_dataVal + 1 and up are compression codes. They encode true data elements: max_dataVal + 1 is the clear code. max_dataVal + 2 is the end code. max_dataVal + 3 and up are string codes. Each string code represents a string of true data elements. The translation from a string code to the string of true data elements varies as the stream progresses. In the beginning and after every clear code, the translation table is empty, so no string codes are valid. As the stream progresses, the table gets filled and more string codes become valid. -----------------------------------------------------------------------------*/ struct decompressor { struct stack stack; int fresh; /* The stream is right after a clear code or at the very beginning */ int codeSize; /* The current code size -- each LZW code in this part of the image is this many bits. Ergo, we read this many bits at a time from the stream. */ int maxnum_code; /* The maximum number of LZW codes that can be represented with the current code size. (1 << codeSize) */ int next_tableSlot; /* Index in the code translation table of the next free entry */ unsigned int firstcode; /* This is always a true data element code */ int prevcode; /* The code just before, in the image, the one we're processing now */ int table[2][(1 << MAX_LZW_BITS)]; /* The following are constant for the life of the decompressor */ FILE * ifP; int init_codeSize; int max_dataVal; int clear_code; int end_code; }; static void resetDecompressor(struct decompressor * const decompP) { decompP->codeSize = decompP->init_codeSize+1; decompP->maxnum_code = 1 << decompP->codeSize; decompP->next_tableSlot = decompP->max_dataVal + 3; decompP->fresh = 1; } static void lzwInit(struct decompressor * const decompP, FILE * const ifP, int const init_codeSize) { if (verbose) pm_message("Image says the initial compression code size is " "%d bits", init_codeSize); decompP->ifP = ifP; decompP->init_codeSize = init_codeSize; assert(decompP->init_codeSize < sizeof(decompP->max_dataVal) * 8); decompP->max_dataVal = (1 << init_codeSize) - 1; decompP->clear_code = decompP->max_dataVal + 1; decompP->end_code = decompP->max_dataVal + 2; if (verbose) pm_message("Initial code size is %u bits; clear code = 0x%x, " "end code = 0x%x", decompP->init_codeSize, decompP->clear_code, decompP->end_code); /* The entries in the translation table for true data codes are constant throughout the stream. We set them now and they never change. */ { unsigned int i; for (i = 0; i <= decompP->max_dataVal; ++i) { decompP->table[0][i] = 0; decompP->table[1][i] = i; } } resetDecompressor(decompP); getCode_init(&getCodeState); decompP->fresh = TRUE; initStack(&decompP->stack, maxnum_lzwCode * 2); } static void lzwTerm(struct decompressor * const decompP) { termStack(&decompP->stack); } static void expandCodeOntoStack(struct decompressor * const decompP, int const incode, const char ** const errorP) { /*---------------------------------------------------------------------------- 'incode' is an LZW string code. It represents a string of true data elements, as defined by the string translation table in *decompP. Expand the code to a string of LZW direct codes and push them onto the stack such that the leftmost code is on top. Also add to the translation table where appropriate. Iff the translation table contains a cycle (which means the LZW stream from which it was built is invalid), fail (return text explanation as *errorP). -----------------------------------------------------------------------------*/ int code; const char * error; error = NULL; /* Initial value */ if (incode < decompP->next_tableSlot) code = incode; else { /* It's a code that isn't in our translation table yet */ pushStack(&decompP->stack, decompP->firstcode); code = decompP->prevcode; } { /* Get the whole string that this compression code represents and push it onto the code stack so the leftmost code is on top. Set decompP->firstcode to the first (leftmost) code in that string. */ unsigned int stringCount; stringCount = 0; while (code > decompP->max_dataVal && !error) { if (stringCount > maxnum_lzwCode) { asprintfN(&error, "Error in GIF image: contains LZW string loop"); } else { ++stringCount; pushStack(&decompP->stack, decompP->table[1][code]); code = decompP->table[0][code]; } } decompP->firstcode = decompP->table[1][code]; pushStack(&decompP->stack, decompP->firstcode); } if (decompP->next_tableSlot < maxnum_lzwCode) { decompP->table[0][decompP->next_tableSlot] = decompP->prevcode; decompP->table[1][decompP->next_tableSlot] = decompP->firstcode; ++decompP->next_tableSlot; if (decompP->next_tableSlot >= decompP->maxnum_code) { /* We've used up all the codes of the current code size. Future codes in the stream will have codes one bit longer. But there's an exception if we're already at the LZW maximum, in which case the codes will simply continue the same size. */ if (decompP->codeSize < MAX_LZW_BITS) { ++decompP->codeSize; decompP->maxnum_code = 1 << decompP->codeSize; } } } *errorP = error; decompP->prevcode = incode; } static void lzwReadByteFresh(struct getCodeState * const getCodeStateP, struct decompressor * const decompP, bool * const endOfImageP, unsigned int * const dataReadP, const char ** const errorP) { /* Read off all initial clear codes, read the first non-clear code, and return it. There are no strings in the table yet, so the next code must be a direct true data code. */ bool eof; do { getCode_get(getCodeStateP, decompP->ifP, decompP->codeSize, &eof, &decompP->firstcode, errorP); decompP->prevcode = decompP->firstcode; } while (decompP->firstcode == decompP->clear_code && !*errorP && !eof); if (!*errorP) { if (eof) *endOfImageP = TRUE; else if (decompP->firstcode == decompP->end_code) { if (!zeroDataBlock) readThroughEod(decompP->ifP); *endOfImageP = TRUE; } else { *endOfImageP = FALSE; *dataReadP = decompP->firstcode; } } } static void lzwReadByte(struct decompressor * const decompP, unsigned int * const dataReadP, bool * const endOfImageP, const char ** const errorP) { /*---------------------------------------------------------------------------- Return the next data element of the decompressed image. In the context of a GIF, a data element is the color table index of one pixel. We read and return the next byte of the decompressed image. If we can't, because the stream is too corrupted to make sense out of it or the stream ends, we fail (return text description of why as *errorP). We forgive the case that the "end" code is the end of the stream -- not followed by an EOD marker (zero length DataBlock). Iff we can't read a byte because we've hit the end of the image, we return *endOfImageP = true. -----------------------------------------------------------------------------*/ if (!stackIsEmpty(&decompP->stack)) { *errorP = NULL; *endOfImageP = FALSE; *dataReadP = popStack(&decompP->stack); } else if (decompP->fresh) { decompP->fresh = FALSE; lzwReadByteFresh(&getCodeState, decompP, endOfImageP, dataReadP, errorP); } else { unsigned int code; bool eof; getCode_get(&getCodeState, decompP->ifP, decompP->codeSize, &eof, &code, errorP); if (!*errorP) { if (eof) asprintfN(errorP, "Premature end of file; no proper GIF closing"); else { if (code == decompP->clear_code) { resetDecompressor(decompP); lzwReadByte(decompP, dataReadP, endOfImageP, errorP); } else { if (code == decompP->end_code) { if (!zeroDataBlock) readThroughEod(decompP->ifP); *endOfImageP = TRUE; *errorP = NULL; } else { *endOfImageP = FALSE; expandCodeOntoStack(decompP, code, errorP); if (!*errorP) *dataReadP = popStack(&decompP->stack); } } } } } } enum pass {MULT8PLUS0, MULT8PLUS4, MULT4PLUS2, MULT2PLUS1}; static void bumpRowInterlace(unsigned int * const rowP, unsigned int const rows, enum pass * const passP) { /*---------------------------------------------------------------------------- Move *pixelCursorP to the next row in the interlace pattern. -----------------------------------------------------------------------------*/ /* There are 4 passes: MULT8PLUS0: Rows 8, 16, 24, 32, etc. MULT8PLUS4: Rows 4, 12, 20, 28, etc. MULT4PLUS2: Rows 2, 6, 10, 14, etc. MULT2PLUS1: Rows 1, 3, 5, 7, 9, etc. */ switch (*passP) { case MULT8PLUS0: *rowP += 8; break; case MULT8PLUS4: *rowP += 8; break; case MULT4PLUS2: *rowP += 4; break; case MULT2PLUS1: *rowP += 2; break; } /* Set the proper pass for the next read. Note that if there are more than 4 rows, the sequence of passes is sequential, but when there are fewer than 4, we may skip e.g. from MULT8PLUS0 to MULT4PLUS2. */ while (*rowP >= rows && *passP != MULT2PLUS1) { switch (*passP) { case MULT8PLUS0: *passP = MULT8PLUS4; *rowP = 4; break; case MULT8PLUS4: *passP = MULT4PLUS2; *rowP = 2; break; case MULT4PLUS2: *passP = MULT2PLUS1; *rowP = 1; break; case MULT2PLUS1: /* We've read the entire image */ break; } } } struct pnmBuffer { xel ** xels; unsigned int col; unsigned int row; }; static void addPixelToRaster(unsigned int const cmapIndex, struct pnmBuffer * const pnmBufferP, unsigned int const cols, unsigned int const rows, gifColorMap cmap, unsigned int const cmapSize, bool const interlace, int const transparentIndex, bit ** const alphabits, enum pass * const passP) { if (cmapIndex >= cmapSize) pm_error("Invalid color index %u in an image that has only " "%u colors in the color map.", cmapIndex, cmapSize); assert(cmapIndex < MAXCOLORMAPSIZE); PPM_ASSIGN(pnmBufferP->xels[pnmBufferP->row][pnmBufferP->col], cmap[CM_RED][cmapIndex], cmap[CM_GRN][cmapIndex], cmap[CM_BLU][cmapIndex]); if (alphabits) alphabits[pnmBufferP->row][pnmBufferP->col] = (cmapIndex == transparentIndex) ? PBM_BLACK : PBM_WHITE; ++pnmBufferP->col; if (pnmBufferP->col == cols) { pnmBufferP->col = 0; if (interlace) bumpRowInterlace(&pnmBufferP->row, rows, passP); else ++pnmBufferP->row; } } static void verifyPixelRead(bool const endOfImage, const char * const readError, unsigned int const cols, unsigned int const rows, unsigned int const failedRowNum, const char ** const errorP) { if (readError) *errorP = strdup(readError); else { if (endOfImage) asprintfN(errorP, "Error in GIF image: Not enough raster data to fill " "%u x %u dimensions. Ran out of raster data in " "row %u. The image has proper ending sequence, so " "this is not just a truncated file.", cols, rows, failedRowNum); else *errorP = NULL; } } static void readRaster(struct decompressor * const decompP, xel ** const xels, unsigned int const cols, unsigned int const rows, gifColorMap cmap, unsigned int const cmapSize, bool const interlace, int const transparentIndex, bit ** const alphabits, bool const tolerateBadInput) { struct pnmBuffer pnmBuffer; enum pass pass; bool fillingMissingPixels; pass = MULT8PLUS0; pnmBuffer.xels = xels; pnmBuffer.col = 0; pnmBuffer.row = 0; fillingMissingPixels = false; /* initial value */ while (pnmBuffer.row < rows) { unsigned int colorIndex; if (fillingMissingPixels) colorIndex = 0; else { const char * error; const char * readError; unsigned int readColorIndex; bool endOfImage; lzwReadByte(decompP, &readColorIndex, &endOfImage, &readError); verifyPixelRead(endOfImage, readError, cols, rows, pnmBuffer.row, &error); if (readError) strfree(readError); if (error) { if (tolerateBadInput) { pm_message("WARNING: %s. " "Filling bottom %u rows with arbitrary color", error, rows - pnmBuffer.row); fillingMissingPixels = true; } else pm_error("Unable to read input image. %s. Use the " "-repair option to try to salvage some of " "the image", error); colorIndex = 0; } else colorIndex = readColorIndex; } addPixelToRaster(colorIndex, &pnmBuffer, cols, rows, cmap, cmapSize, interlace, transparentIndex, alphabits, &pass); } } static void skipExtraneousData(struct decompressor * const decompP) { unsigned int byteRead; bool endOfImage; const char * error; lzwReadByte(decompP, &byteRead, &endOfImage, &error); if (error) strfree(error); else if (!endOfImage) { pm_message("Extraneous data at end of image. " "Skipped to end of image"); while (!endOfImage && !error) lzwReadByte(decompP, &byteRead, &endOfImage, &error); if (error) { pm_message("Error encountered skipping to end of image: %s", error); strfree(error); } } } static void readImageData(FILE * const ifP, xel ** const xels, unsigned int const cols, unsigned int const rows, gifColorMap cmap, unsigned int const cmapSize, bool const interlace, int const transparentIndex, bit ** const alphabits, bool const tolerateBadInput) { unsigned char lzwMinCodeSize; struct decompressor decomp; bool gotMinCodeSize; gotMinCodeSize = ReadOK(ifP, &lzwMinCodeSize, 1); if (!gotMinCodeSize) pm_error("GIF stream ends (or read error) " "right after an image separator; no " "image data follows."); if (lzwMinCodeSize > MAX_LZW_BITS) pm_error("Invalid minimum code size value in image data: %u. " "Maximum allowable code size in GIF is %u", lzwMinCodeSize, MAX_LZW_BITS); lzwInit(&decomp, ifP, lzwMinCodeSize); readRaster(&decomp, xels, cols, rows, cmap, cmapSize, interlace, transparentIndex, alphabits, tolerateBadInput); skipExtraneousData(&decomp); lzwTerm(&decomp); } static void writePnm(FILE * const outfileP, xel ** const xels, int const cols, int const rows, int const hasGray, int const hasColor) { /*---------------------------------------------------------------------------- Write a PNM image to the current position of file *outfileP with dimensions 'cols' x 'rows' and raster 'xels'. Make it PBM, PGM, or PBM according to 'hasGray' and 'hasColor'. -----------------------------------------------------------------------------*/ int format; const char * formatName; if (hasColor) { format = PPM_FORMAT; formatName = "PPM"; } else if (hasGray) { format = PGM_FORMAT; formatName = "PGM"; } else { format = PBM_FORMAT; formatName = "PBM"; } if (verbose) pm_message("writing a %s file", formatName); if (outfileP) pnm_writepnm(outfileP, xels, cols, rows, (xelval) GIFMAXVAL, format, FALSE); } static void transparencyMessage(int const transparentIndex, gifColorMap cmap) { /*---------------------------------------------------------------------------- If user wants verbose output, tell him that the color with index 'transparentIndex' is supposed to be a transparent background color. If transparentIndex == -1, tell him there is no transparent background color. -----------------------------------------------------------------------------*/ if (verbose) { if (transparentIndex == -1) pm_message("no transparency"); else pm_message("transparent background color: rgb:%02x/%02x/%02x " "Index %d", cmap[CM_RED][transparentIndex], cmap[CM_GRN][transparentIndex], cmap[CM_BLU][transparentIndex], transparentIndex ); } } static void readGifHeader(FILE * const gifFile, struct gifScreen * const gifScreenP) { /*---------------------------------------------------------------------------- Read the GIF stream header off the file gifFile, which is present positioned to the beginning of a GIF stream. Return the info from it as *gifScreenP. -----------------------------------------------------------------------------*/ unsigned char buf[16]; char version[4]; if (! ReadOK(gifFile,buf,6)) pm_error("error reading magic number" ); if (strncmp((char *)buf,"GIF",3) != 0) pm_error("File does not contain a GIF stream. It does not start " "with 'GIF'."); strncpy(version, (char *)buf + 3, 3); version[3] = '\0'; if (verbose) pm_message("GIF format version is '%s'", version); if ((!streq(version, "87a")) && (!streq(version, "89a"))) pm_error("bad version number, not '87a' or '89a'" ); if (! ReadOK(gifFile,buf,7)) pm_error("failed to read screen descriptor" ); gifScreenP->Width = LM_to_uint(buf[0],buf[1]); gifScreenP->Height = LM_to_uint(buf[2],buf[3]); gifScreenP->ColorMapSize = 1 << ((buf[4] & 0x07) + 1); gifScreenP->ColorResolution = (buf[4] & 0x70 >> 3) + 1; gifScreenP->Background = buf[5]; gifScreenP->AspectRatio = buf[6]; if (verbose) { pm_message("GIF Width = %d GIF Height = %d " "Pixel aspect ratio = %d (%f:1)", gifScreenP->Width, gifScreenP->Height, gifScreenP->AspectRatio, gifScreenP->AspectRatio == 0 ? 1 : (gifScreenP->AspectRatio + 15) / 64.0); pm_message("Colors = %d Color Resolution = %d", gifScreenP->ColorMapSize, gifScreenP->ColorResolution); } if (BitSet(buf[4], LOCALCOLORMAP)) { /* Global Colormap */ readColorMap(gifFile, gifScreenP->ColorMapSize, gifScreenP->ColorMap, &gifScreenP->hasGray, &gifScreenP->hasColor); if (verbose) { pm_message("Color map %s grays, %s colors", gifScreenP->hasGray ? "contains" : "doesn't contain", gifScreenP->hasColor ? "contains" : "doesn't contain"); } } if (gifScreenP->AspectRatio != 0 && gifScreenP->AspectRatio != 49) { float r; r = ( (float) gifScreenP->AspectRatio + 15.0 ) / 64.0; pm_message("warning - input pixels are not square, " "but we are rendering them as square pixels " "in the output. " "To fix the output, run it through " "'pnmscale -%cscale %g'", r < 1.0 ? 'x' : 'y', r < 1.0 ? 1.0 / r : r ); } } static void readExtensions(FILE* const ifP, struct gif89 * const gif89P, bool * const eodP, const char ** const errorP) { /*---------------------------------------------------------------------------- Read extension blocks from the GIF stream to which the file *ifP is positioned. Read up through the image separator that begins the next image or GIF stream terminator. If we encounter EOD (end of GIF stream) before we find an image separator, we return *eodP == TRUE. Else *eodP == FALSE. If we hit end of file before an EOD marker, we fail. -----------------------------------------------------------------------------*/ bool imageStart; bool eod; *errorP = NULL; /* initial value */ eod = FALSE; imageStart = FALSE; /* Read the image descriptor */ while (!imageStart && !eod && !*errorP) { unsigned char c; const char * error; readFile(ifP, &c, 1, &error); if (error) { asprintfN(errorP, "File read error where start of image " "descriptor or end of GIF expected. %s", error); strfree(error); } else { if (c == ';') { /* GIF terminator */ eod = TRUE; } else if (c == '!') { /* Extension */ unsigned char functionCode; const char * error; readFile(ifP, &functionCode, 1, &error); if (error) { asprintfN(errorP, "Failed to read function code " "of GIF extension (immediately after the '!' " "extension delimiter) from input. %s", error); strfree(error); } else { doExtension(ifP, functionCode, gif89P); } } else if (c == ',') imageStart = TRUE; else pm_message("bogus character 0x%02x, ignoring", (int)c); } } *eodP = eod; } static void reportImageInfo(unsigned int const cols, unsigned int const rows, bool const useGlobalColormap, unsigned int const localColorMapSize, bool const interlaced) { pm_message("reading %u by %u%s GIF image", cols, rows, interlaced ? " interlaced" : "" ); if (useGlobalColormap) pm_message(" Uses global colormap"); else pm_message(" Uses local colormap of %u colors", localColorMapSize); } static void convertImage(FILE * const ifP, bool const skipIt, FILE * const imageout_file, FILE * const alphafile, struct gifScreen gifScreen, struct gif89 const gif89, bool const tolerateBadInput) { /*---------------------------------------------------------------------------- Read a single GIF image from the current position of file 'ifP'. If 'skipIt' is TRUE, don't do anything else. Otherwise, write the image to the current position of files 'imageout_file' and 'alphafile'. If 'alphafile' is NULL, though, don't write any alpha information. -----------------------------------------------------------------------------*/ unsigned char buf[16]; bool useGlobalColormap; xel **xels; /* The image raster, in libpnm format */ bit **alphabits; /* The image alpha mask, in libpbm format. NULL if we aren't computing an alpha mask. */ unsigned int cols, rows; /* Dimensions of the image */ gifColorMap localColorMap; unsigned int localColorMapSize; bool interlaced; if (! ReadOK(ifP,buf,9)) pm_error("couldn't read left/top/width/height"); useGlobalColormap = ! BitSet(buf[8], LOCALCOLORMAP); localColorMapSize = 1u << ((buf[8] & 0x07) + 1); cols = LM_to_uint(buf[4], buf[5]); rows = LM_to_uint(buf[6], buf[7]); interlaced = !!BitSet(buf[8], INTERLACE); if (verbose) reportImageInfo(cols, rows, useGlobalColormap, localColorMapSize, interlaced); xels = pnm_allocarray(cols, rows); if (!xels) pm_error("couldn't alloc space for image" ); if (alphafile) { alphabits = pbm_allocarray(cols, rows); if (!alphabits) pm_error("couldn't alloc space for alpha image" ); } else alphabits = NULL; if (!useGlobalColormap) { int hasGray, hasColor; readColorMap(ifP, localColorMapSize, localColorMap, &hasGray, &hasColor); transparencyMessage(gif89.transparent, localColorMap); readImageData(ifP, xels, cols, rows, localColorMap, localColorMapSize, interlaced, gif89.transparent, alphabits, tolerateBadInput); if (!skipIt) { writePnm(imageout_file, xels, cols, rows, hasGray, hasColor); } } else { transparencyMessage(gif89.transparent, gifScreen.ColorMap); readImageData(ifP, xels, cols, rows, gifScreen.ColorMap, gifScreen.ColorMapSize, interlaced, gif89.transparent, alphabits, tolerateBadInput); if (!skipIt) { writePnm(imageout_file, xels, cols, rows, gifScreen.hasGray, gifScreen.hasColor); } } if (!skipIt && alphafile && alphabits) pbm_writepbm(alphafile, alphabits, cols, rows, FALSE); pnm_freearray(xels, rows); if (alphabits) pbm_freearray(alphabits, rows); } static void disposeOfReadExtensionsError(const char * const error, bool const tolerateBadInput, unsigned int const imageSeq, bool * const eodP) { if (error) { if (tolerateBadInput) pm_message("Error accessing Image %u of stream; no further " "images can be accessed. %s", imageSeq, error); else pm_error("Error accessing Image %u of stream. %s", imageSeq, error); strfree(error); *eodP = TRUE; } } static void convertImages(FILE * const ifP, bool const allImages, int const requestedImageSeq, bool const drainStream, FILE * const imageout_file, FILE * const alphafile, bool const tolerateBadInput) { /*---------------------------------------------------------------------------- Read a GIF stream from file 'ifP' and write one or more images from it as PNM images to file 'imageout_file'. If the images have transparency and 'alphafile' is non-NULL, write PGM alpha masks to file 'alphafile'. 'allImages' means Caller wants all the images in the stream. 'requestedImageSeq' is meaningful only when 'allImages' is FALSE. It is the sequence number of the one image Caller wants from the stream, with the first image being 0. 'drainInput' means to read the entire GIF stream, even after reading the image Caller asked for. We read the stream, not just the file it's in, so we still recognize certain errors in the GIF format in the tail of the stream and there may yet be more stuff in the file when we return. -----------------------------------------------------------------------------*/ int imageSeq; /* Sequence within GIF stream of image we are currently processing. First is 0. */ struct gifScreen gifScreen; struct gif89 gif89; bool eod; /* We've read through the GIF terminator character */ initGif89(&gif89); readGifHeader(ifP, &gifScreen); for (imageSeq = 0, eod = FALSE; !eod && (imageSeq <= requestedImageSeq || allImages || drainStream); ++imageSeq) { const char * error; readExtensions(ifP, &gif89, &eod, &error); disposeOfReadExtensionsError(error, tolerateBadInput, imageSeq, &eod); if (eod) { /* GIF stream ends before image with sequence imageSeq */ if (!allImages && (imageSeq <= requestedImageSeq)) pm_error("You requested Image %d, but " "only %d image%s found in GIF stream", requestedImageSeq + 1, imageSeq, imageSeq > 1 ? "s" : ""); } else { if (verbose) pm_message("Reading Image Sequence %d", imageSeq); convertImage(ifP, !allImages && (imageSeq != requestedImageSeq), imageout_file, alphafile, gifScreen, gif89, tolerateBadInput); } } } int main(int argc, char **argv) { struct cmdlineInfo cmdline; FILE *ifP; FILE *alpha_file, *imageout_file; pnm_init(&argc, argv); parseCommandLine(argc, argv, &cmdline); verbose = cmdline.verbose; showComment = cmdline.comments; ifP = pm_openr(cmdline.input_filespec); if (cmdline.alpha_filename == NULL) alpha_file = NULL; else alpha_file = pm_openw(cmdline.alpha_filename); if (alpha_file && streq(cmdline.alpha_filename, "-")) imageout_file = NULL; else imageout_file = stdout; convertImages(ifP, cmdline.all_images, cmdline.image_no, !cmdline.quitearly, imageout_file, alpha_file, cmdline.repair); pm_close(ifP); if (imageout_file != NULL) pm_close(imageout_file); if (alpha_file != NULL) pm_close(alpha_file); return 0; }