ximagif.cpp

用Cximage 库显示各种格式图片小程序

			free_ent=(short)(ClearCode+2);
			clear_flg=1;
			output((code_int)ClearCode);
		}
	}
	 // Put out the final code.
	output( (code_int)ent );
	output( (code_int) EOFCode );
}
////////////////////////////////////////////////////////////////////////////////

static const unsigned long code_mask[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
								  0x001F, 0x003F, 0x007F, 0x00FF,
								  0x01FF, 0x03FF, 0x07FF, 0x0FFF,
								  0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };

////////////////////////////////////////////////////////////////////////////////
void CxImageGIF::output( code_int  code)
{
	cur_accum &= code_mask[ cur_bits ];

	if( cur_bits > 0 )
		cur_accum |= ((long)code << cur_bits);
	else
		cur_accum = code;

	cur_bits += n_bits;

	while( cur_bits >= 8 ) {
		char_out( (unsigned int)(cur_accum & 0xff) );
		cur_accum >>= 8;
		cur_bits -= 8;
	}

	/*
	 * If the next entry is going to be too big for the code size,
	 * then increase it, if possible.
	 */

	if ( free_ent > maxcode || clear_flg ) {
		if( clear_flg ) {
			maxcode = (short)MAXCODE(n_bits = g_init_bits);
			clear_flg = 0;
		} else {
			++n_bits;
			if ( n_bits == MAXBITSCODES )
				maxcode = (code_int)1 << MAXBITSCODES; /* should NEVER generate this code */
			else
				maxcode = (short)MAXCODE(n_bits);
		}
	}
	
	if( code == EOFCode ) {
		 // At EOF, write the rest of the buffer.
		while( cur_bits > 0 ) {
			char_out( (unsigned int)(cur_accum & 0xff) );
			cur_accum >>= 8;
			cur_bits -= 8;
		}
	
		flush_char();
		g_outfile->Flush();

		if(g_outfile->Error()) strcpy(info.szLastError,"Write Error in GIF file");
	}
}
////////////////////////////////////////////////////////////////////////////////

void CxImageGIF::cl_hash(long hsize)

{
	register long *htab_p = htab+hsize;

	register long i;
	register long m1 = -1L;

	i = hsize - 16;

	do {
		*(htab_p-16)=m1;
		*(htab_p-15)=m1;
		*(htab_p-14)=m1;
		*(htab_p-13)=m1;
		*(htab_p-12)=m1;
		*(htab_p-11)=m1;
		*(htab_p-10)=m1;
		*(htab_p-9)=m1;
		*(htab_p-8)=m1;
		*(htab_p-7)=m1;
		*(htab_p-6)=m1;
		*(htab_p-5)=m1;
		*(htab_p-4)=m1;
		*(htab_p-3)=m1;
		*(htab_p-2)=m1;
		*(htab_p-1)=m1;
		
		htab_p-=16;
	} while ((i-=16) >=0);

	for (i+=16;i>0;--i)
		*--htab_p=m1;
}

/*******************************************************************************
*   GIF specific
*******************************************************************************/

void CxImageGIF::char_out(int c)
{
	accum[a_count++]=(char)c;
	if (a_count >=254)
		flush_char();
}

void CxImageGIF::flush_char()
{
	if (a_count > 0) {
		g_outfile->PutC((BYTE)a_count);
		g_outfile->Write(accum,1,a_count);
		a_count=0;
	}
}

/*******************************************************************************
*   GIF decoder
*******************************************************************************/
/* DECODE.C - An LZW decoder for GIF
 * Copyright (C) 1987, by Steven A. Bennett
 * Copyright (C) 1994, C++ version by Alejandro Aguilar Sierra
*
 * Permission is given by the author to freely redistribute and include
 * this code in any program as long as this credit is given where due.
 *
 * In accordance with the above, I want to credit Steve Wilhite who wrote
 * the code which this is heavily inspired by...
 *
 * GIF and 'Graphics Interchange Format' are trademarks (tm) of
 * Compuserve, Incorporated, an H&R Block Company.
 *
 * Release Notes: This file contains a decoder routine for GIF images
 * which is similar, structurally, to the original routine by Steve Wilhite.
 * It is, however, somewhat noticably faster in most cases.
 *
 */

////////////////////////////////////////////////////////////////////////////////

short CxImageGIF::init_exp(short size)
{
	curr_size = (short)(size + 1);
	top_slot = (short)(1 << curr_size);
	clear = (short)(1 << size);
	ending = (short)(clear + 1);
	slot = newcodes = (short)(ending + 1);
	navail_bytes = nbits_left = 0;

	memset(stack,0,MAX_CODES + 1);
	memset(prefix,0,MAX_CODES + 1);
	memset(suffix,0,MAX_CODES + 1);
	return(0);
}
////////////////////////////////////////////////////////////////////////////////

/* get_next_code()
 * - gets the next code from the GIF file.  Returns the code, or else
 * a negative number in case of file errors...
 */
short CxImageGIF::get_next_code(CxFile* file)
{
	short i, x;
	DWORD ret;

	if (nbits_left == 0) {
		if (navail_bytes <= 0) {
			/* Out of bytes in current block, so read next block */
			pbytes = byte_buff;
			if ((navail_bytes = (short)get_byte(file)) < 0)
				return(navail_bytes);
			else if (navail_bytes) {
				for (i = 0; i < navail_bytes; ++i) {
					if ((x = (short)get_byte(file)) < 0) return(x);
					byte_buff[i] = (BYTE)x;
				}
			}
		}
		b1 = *pbytes++;
		nbits_left = 8;
		--navail_bytes;
	}

	if (navail_bytes<0) return ending; // prevent deadlocks (thanks to Mike Melnikov)

	ret = b1 >> (8 - nbits_left);
	while (curr_size > nbits_left){
		if (navail_bytes <= 0){
			/* Out of bytes in current block, so read next block*/
			pbytes = byte_buff;
			if ((navail_bytes = (short)get_byte(file)) < 0)
				return(navail_bytes);
			else if (navail_bytes){
				for (i = 0; i < navail_bytes; ++i){
					if ((x = (short)get_byte(file)) < 0) return(x);
					byte_buff[i] = (BYTE)x;
				}
			}
		}
		b1 = *pbytes++;
		ret |= b1 << nbits_left;
		nbits_left += 8;
		--navail_bytes;
	}
	nbits_left = (short)(nbits_left-curr_size);
	ret &= code_mask[curr_size];
	return((short)(ret));
}
////////////////////////////////////////////////////////////////////////////////

/* short decoder(linewidth)
 *    short linewidth;               * Pixels per line of image *
 *
 * - This function decodes an LZW image, according to the method used
 * in the GIF spec.  Every *linewidth* "characters" (ie. pixels) decoded
 * will generate a call to out_line(), which is a user specific function
 * to display a line of pixels.  The function gets it's codes from
 * get_next_code() which is responsible for reading blocks of data and
 * seperating them into the proper size codes.  Finally, get_byte() is
 * the global routine to read the next BYTE from the GIF file.
 *
 * It is generally a good idea to have linewidth correspond to the actual
 * width of a line (as specified in the Image header) to make your own
 * code a bit simpler, but it isn't absolutely necessary.
 *
 * Returns: 0 if successful, else negative.  (See ERRS.H)
 *
 */
/* bad_code_count is incremented each time an out of range code is read.
 * When this value is non-zero after a decode, your GIF file is probably
 * corrupt in some way...
 */
short CxImageGIF::decoder(CxFile* file, CImageIterator* iter, short linewidth, int &bad_code_count)
{
	register BYTE *sp, *bufptr;
	BYTE *buf;
	register short code, fc, oc, bufcnt;
	short c, size, ret;

	/* Initialize for decoding a new image... */
	bad_code_count = 0;
	if ((size = (short)get_byte(file)) < 0)	return(size);
	if (size < 2 || 9 < size)				return(BAD_CODE_SIZE);
	// out_line = outline;
	init_exp(size);
	//printf("L %d %x\n",linewidth,size);

	/* Initialize in case they forgot to put in a clear code.
	 * (This shouldn't happen, but we'll try and decode it anyway...)
	 */
	oc = fc = 0;

   /* Allocate space for the decode buffer */
	if ((buf = new BYTE[linewidth + 1]) == NULL) return(OUT_OF_MEMORY);

   /* Set up the stack pointer and decode buffer pointer */
	sp = stack;
	bufptr = buf;
	bufcnt = linewidth;

   /* This is the main loop.  For each code we get we pass through the
	* linked list of prefix codes, pushing the corresponding "character" for
	* each code onto the stack.  When the list reaches a single "character"
	* we push that on the stack too, and then start unstacking each
    * character for output in the correct order.  Special handling is
	* included for the clear code, and the whole thing ends when we get
    * an ending code.
    */
	while ((c = get_next_code(file)) != ending) {
		/* If we had a file error, return without completing the decode*/
		if (c < 0){
			delete [] buf;
			return(0);
		}
		/* If the code is a clear code, reinitialize all necessary items.*/
		if (c == clear){
			curr_size = (short)(size + 1);
			slot = newcodes;
			top_slot = (short)(1 << curr_size);

			/* Continue reading codes until we get a non-clear code
			* (Another unlikely, but possible case...)
			*/
			while ((c = get_next_code(file)) == clear);

			/* If we get an ending code immediately after a clear code
			* (Yet another unlikely case), then break out of the loop.
			*/
			if (c == ending) break;

			/* Finally, if the code is beyond the range of already set codes,
			* (This one had better NOT happen...  I have no idea what will
			* result from this, but I doubt it will look good...) then set it
			* to color zero.
			*/
			if (c >= slot) c = 0;
			oc = fc = c;

			/* And let us not forget to put the char into the buffer... And
			* if, on the off chance, we were exactly one pixel from the end
			* of the line, we have to send the buffer to the out_line()
			* routine...
			*/
			*bufptr++ = (BYTE)c;
			if (--bufcnt == 0) {
				if (iter) {
					if ((ret = (short)out_line(iter, buf, linewidth)) < 0) {
						delete [] buf;
						return(ret);
					}
				}
				bufptr = buf;
				bufcnt = linewidth;
            }
		} else {
			/* In this case, it's not a clear code or an ending code, so
			* it must be a code code...  So we can now decode the code into
			* a stack of character codes. (Clear as mud, right?)
			*/
			code = c;

			/* Here we go again with one of those off chances...  If, on the
			* off chance, the code we got is beyond the range of those already
			* set up (Another thing which had better NOT happen...) we trick
			* the decoder into thinking it actually got the last code read.
			* (Hmmn... I'm not sure why this works...  But it does...)
			*/
			if (code >= slot && sp<(stack+MAX_CODES-1)) {
				if (code > slot)
					++bad_code_count;
				code = oc;
				*sp++ = (BYTE)fc;
            }

			/* Here we scan back along the linked list of prefixes, pushing
			* helpless characters (ie. suffixes) onto the stack as we do so.
			*/
			while (code >= newcodes && sp<(stack+MAX_CODES-1)) {
				*sp++ = suffix[code];
				code = prefix[code];
            }

			/* Push the last character on the stack, and set up the new
			* prefix and suffix, and if the required slot number is greater
			* than that allowed by the current bit size, increase the bit
			* size.  (NOTE - If we are all full, we *don't* save the new
			* suffix and prefix...  I'm not certain if this is correct...
			* it might be more proper to overwrite the last code...
			*/
			*sp++ = (BYTE)code;
			if (slot < top_slot){
				suffix[slot] = (BYTE)(fc = (BYTE)code);
				prefix[slot++] = oc;
				oc = c;
            }
			if (slot >= top_slot){
				if (curr_size < 12) {
					top_slot <<= 1;
					++curr_size;
				}
			}

			/* Now that we've pushed the decoded string (in reverse order)
			* onto the stack, lets pop it off and put it into our decode
			* buffer...  And when the decode buffer is full, write another
			* line...
			*/
			while (sp > stack) {
				*bufptr++ = *(--sp);
				if (--bufcnt == 0) {
					if (iter) {
						if ((ret = (short)out_line(iter, buf, linewidth)) < 0) {
							delete [] buf;
							return(ret);
						}
					}
					bufptr = buf;
					bufcnt = linewidth;
				}
			}
		}
	}
	ret = 0;
	if (bufcnt != linewidth && iter)
		ret = (short)out_line(iter, buf, (linewidth - bufcnt));
	delete [] buf;
	return(ret);
}
////////////////////////////////////////////////////////////////////////////////
int CxImageGIF::get_num_frames(CxFile *fp,struct_TabCol* TabColSrc,struct_dscgif* dscgif)
{
	struct_image image;

	long pos=fp->Tell();
	int nframes=0;

	struct_TabCol TempTabCol;
	memcpy(&TempTabCol,TabColSrc,sizeof(struct_TabCol));

	char ch;
	bool bPreviousWasNull = true;

	for (BOOL bContinue = TRUE; bContinue; )
	{