summaryrefslogtreecommitdiffstats
path: root/tools/gifconv/decompress.c
blob: abccb7ff27bc5945e18def7bb8a1ea74d1d865b8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
#include <stdio.h>
#include <stdlib.h>
#include "gif.h"

#define NEXTBYTE (*ptr++)
#define IMAGESEP 0x2c
#define INTERLACEMASK 0x40
#define COLORMAPMASK 0x80
#define False 0
#define True 1

WORD           iWIDE,iHIGH,eWIDE,eHIGH,expand,numcols,strip,nostrip;
unsigned long  cols[256];
char           *cmd;

FILE *fp;

static int BitOffset = 0,	/* Bit Offset of next code */
XC = 0, YC = 0,				/* Output X and Y coords of current pixel */
Pass = 0,					/* Used by output routine if WORDerlaced pic */
OutCount = 0,				/* Decompressor output 'stack count' */
IWidth, IHeight,			/* image dimensions */
BytesPerScanline,			/* Bytes per scanline in output raster */
CodeSize,					/* Code size, read from GIF header */
InitCodeSize,				/* Starting code size, used during Clear */
Code,						/* Value returned by ReadCode */
MaxCode,					/* limiting value for current code size */
ClearCode,					/* GIF clear code */
EOFCode,					/* GIF end-of-information code */
CurCode, OldCode, InCode,	/* Decompressor variables */
FirstFree,					/* First free code, generated per GIF spec */
FreeCode,					/* Decompressor, next free slot in hash table */
FinChar,					/* Decompressor variable */
DataMask,					/* AND mask for data size */
ReadMask;                   /* Code AND mask for current code size */

/*MODIFICATIONS*/
BYTE tempbyte[10];
BYTE * tempBYTEptr[10];
WORD tempint[10];
WORD ImageCount = 0;
/*END MODIFICATION*/

boolean Interlace, HasColormap;


BYTE *Image;			/* The result array */
BYTE *RawGIF;			/* The heap array to hold it, raw */
BYTE *Raster;			/* The raster data stream, unblocked */

/* The hash table used by the decompressor */

int Prefix[4096];
int Suffix[4096];

/* An output array used by the decompressor */

int OutCode[1025];

/* The color map, read from the GIF header */

int  numused;

/* Fetch the next code from the raster data stream.  The codes can be
* any length from 3 to 12 bits, packed WORDo 8-bit BYTEs, so we have to
* maWORDain our location in the Raster array as a BIT Offset.  We compute
* the BYTE Offset WORDo the raster array by dividing this by 8, pick up
* three BYTEs, compute the bit Offset WORDo our 24-bit chunk, shift to
* bring the desired code to the bottom, then mask it off and return it. 
*/
static int ReadCode(void)
{
	int RawCode, ByteOffset;
	
    ByteOffset = BitOffset / 8;
    RawCode = Raster[ByteOffset] + (0x100 * Raster[ByteOffset + 1]);
    if (CodeSize >= 8)
		RawCode += (0x10000 * Raster[ByteOffset + 2]);
    RawCode >>= (BitOffset % 8);
    BitOffset += CodeSize;
    return(RawCode & ReadMask);
}


static void AddToPixel(BYTE Index)
{
    if (YC<IHeight)
        *(Image + YC * BytesPerScanline + XC) = Index;
	

    
    /* Update the X-coordinate, and if it overflows, update the Y-coordinate */
    if (++XC == IWidth) {
		
	/* If a non-WORDerlaced picture, just increment YC to the next scan line. 
	* If it's WORDerlaced, deal with the WORDerlace as described in the GIF
	* spec.  Put the decoded scan line out to the screen if we haven't gone
	* past the bottom of it.
		*/
		
		XC = 0;
		if (!Interlace) YC++;
		else {
			switch (Pass) {
			case 0:
				YC += 8;
				if (YC >= IHeight) {
					Pass++;
					YC = 4;
				}
				break;
			case 1:
				YC += 8;
				if (YC >= IHeight) {
					Pass++;
					YC = 2;
				}
				break;
				
			case 2:
				YC += 4;
				if (YC >= IHeight) {
					Pass++;
					YC = 1;
				}
				break;
			case 3:
				YC += 2;
				break;
			default:
				break;
			}
		}
    }
}

/* Main routine.  Convert a GIF image to an HDF image */

BYTE* Decompress(GifImageDesc , GifHead)
GIFIMAGEDESC *GifImageDesc;
GIFHEAD      *GifHead;
{
	int i;

	XC = 0; 
	YC = 0;
	Pass = 0;
	OutCount = 0;
	BitOffset = 0;
	
	DataMask = (WORD)((1L << ((GifHead->PackedField & 0x07) +1)) -1);
	Raster = GifImageDesc->GIFImage;
	
	
	/* Check for image seperator */
	
	/* Now read in values from the image descriptor */
	IWidth = GifImageDesc->ImageWidth;
	IHeight = GifImageDesc->ImageHeight;
	Interlace = GifImageDesc->PackedField & 0x40;
	
	/* Note that I ignore the possible existence of a local color map.
	* I'm told there aren't many files around that use them, and the spec
	* says it's defined for future use.  This could lead to an error
	* reading some files. 
	*/
	
	/* Start reading the raster data. First we get the WORDial code size
	* and compute decompressor constant values, based on this code size.
	*/
	
	CodeSize = GifImageDesc->CodeSize;
	ClearCode = (1 << CodeSize);
	EOFCode = ClearCode + 1;
	FreeCode = FirstFree = ClearCode + 2;
	
	/* The GIF spec has it that the code size is the code size used to
	* compute the above values is the code size given in the file, but the
	* code size used in compression/decompression is the code size given in
	* the file plus one. (thus the ++).
	*/
	
	CodeSize++;
	InitCodeSize = CodeSize;
	MaxCode = (1 << CodeSize);
	ReadMask = MaxCode - 1;
	
	/* Read the raster data.  Here we just transpose it from the GIF array
	* to the Raster array, turning it from a series of blocks WORDo one long
	* data stream, which makes life much easier for ReadCode().
	*/
	
	
	
	/*    free(RawGIF);		 We're not done just yet - change made */
	
	/* Allocate the Image */
	
	if (!(Image = (BYTE *)malloc((size_t)IWidth*(size_t)IHeight))) {
		printf("Out of memory");
		exit(-1);
	}
	
	BytesPerScanline = IWidth;
	
	/* Decompress the file, continuing until you see the GIF EOF code.
	* One obvious enhancement is to add checking for corrupt files here.
	*/
	
	Code = ReadCode();
	while (Code != EOFCode) {
		
	/* Clear code sets everything back to its initial value, then reads the
	* immediately subsequent code as uncompressed data.
		*/
		
		if (Code == ClearCode) {
			CodeSize = InitCodeSize;
			MaxCode = (1 << CodeSize);
			ReadMask = MaxCode - 1;
			FreeCode = FirstFree;
			CurCode = OldCode = Code = ReadCode();
			FinChar = CurCode & DataMask;
			AddToPixel(FinChar);
		}
		else {
			
			/* If not a clear code, then must be data: save same as CurCode and InCode */
			
			CurCode = InCode = Code;
			
			/* If greater or equal to FreeCode, not in the hash table yet;
			* repeat the last character decoded
			*/
			
			if (CurCode >= FreeCode) {
				CurCode = OldCode;
				OutCode[OutCount++] = FinChar;
			}
			
			/* Unless this code is raw data, pursue the chain poWORDed to by CurCode
			* through the hash table to its end; each code in the chain puts its
			* associated output code on the output queue.
			*/
			
			while (CurCode > DataMask) {
				if (OutCount > 1024) {
					/*return error message*/	
				}
				OutCode[OutCount++] = Suffix[CurCode];
				CurCode = Prefix[CurCode];
			}
			
			/* The last code in the chain is treated as raw data. */
			
			FinChar = CurCode & DataMask;
			OutCode[OutCount++] = FinChar;
			
			/* Now we put the data out to the Output routine.
			* It's been stacked LIFO, so deal with it that way...
			*/
			
			for (i = OutCount - 1; i >= 0; i--)
				AddToPixel(OutCode[i]);
			OutCount = 0;
			
			/* Build the hash table on-the-fly. No table is stored in the file. */
			
			Prefix[FreeCode] = OldCode;
			Suffix[FreeCode] = FinChar;
			OldCode = InCode;
			
			/* PoWORD to the next slot in the table.  If we exceed the current
			* MaxCode value, increment the code size unless it's already 12.  If it
			* is, do nothing: the next code decompressed better be CLEAR
			*/
			
			FreeCode++;
			if (FreeCode >= MaxCode) {
				if (CodeSize < 12) {
					CodeSize++;
					MaxCode *= 2;
					ReadMask = (1 << CodeSize) - 1;
				}
			}
		}
		Code = ReadCode();
	}

	return Image;	
}