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// Copyright (C) 2019
// Smithsonian Astrophysical Observatory, Cambridge, MA, USA
// For conditions of distribution and use, see copyright notice in "copyright"
#ifndef __tkagif_h__
#define __tkagif_h__
/*
* Algorithm: use open addressing double hashing (no chaining) on the
* prefix code / next character combination. We do a variant of Knuth's
* algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
* secondary probe. Here, the modular division first probe is gives way to
* a faster exclusive-or manipulation. Also do block compression with an
* adaptive reset, whereby the code table is cleared when the compression
* ratio decreases, but after the table fills. The variable-length output
* codes are re-sized at this point, and a special CLEAR code is generated
* for the decompressor. Late addition: construct the table according to
* file size for noticeable speed improvement on small files. Please
* direct questions about this implementation to ames!jaw.
*
* To save much memory, we overlay the table used by compress() with those
* used by decompress(). The tab_prefix table is the same size and type as
* the codeTable. The tab_suffix table needs 2**GIFBITS characters. We get
* this from the beginning of hashTable. The output stack uses the rest of
* hashTable, and contains characters. There is plenty of room for any
* possible stack (stack used to be 8000 characters).
*/
#define HSIZE 5003 /* 80% occupancy */
typedef struct {
int count;
unsigned char red;
unsigned char green;
unsigned char blue;
} Color;
typedef struct {
unsigned char red;
unsigned char green;
unsigned char blue;
} Pixel;
class TkAGIF {
private:
Tcl_Interp* interp_;
ofstream* out_;
int width_;
int height_;
int resolution_;
unsigned char* pict_;
long pictCount_;
Color* colorTable_;
int colorTableSize_;
long maxCode_; // Maximum code, given numBits
int clearCode_;
int eofCode_;
int initialBits_;
int numBits_;
int currentBits_;
int clearFlag_;
int freeEntry_; // First unused entry
int hashTable_[HSIZE];
unsigned char packetAccumulator_[256];
int accumulatedByteCount_;
unsigned long currentAccumulated_;
private:
void initColorTable();
void scanImage(Pixel*);
void compress();
int input();
void output(long);
void clearForBlock();
void clearHashTable();
void charOut(int);
void flushChar();
public:
TkAGIF(Tcl_Interp*);
int create(int, const char*[]);
int add(int, const char*[]);
int close(int, const char*[]);
};
extern TkAGIF* tkagif;
#endif
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