www.pudn.com > uCOS-uCGUI-FATFs.rar > jdct.h, change:2004-08-18,size:6761b


/* 
 * jdct.h 
 * 
 * Copyright (C) 1994-1996, 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 include file contains common declarations for the forward and 
 * inverse DCT modules.  These declarations are private to the DCT managers 
 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms. 
 * The individual DCT algorithms are kept in separate files to ease  
 * machine-dependent tuning (e.g., assembly coding). 
 */ 
 
 
/* 
 * A forward DCT routine is given a pointer to a work area of type DCTELEM[]; 
 * the DCT is to be performed in-place in that buffer.  Type DCTELEM is int 
 * for 8-bit samples, INT32 for 12-bit samples.  (NOTE: Floating-point DCT 
 * implementations use an array of type FAST_FLOAT, instead.) 
 * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE). 
 * The DCT outputs are returned scaled up by a factor of 8; they therefore 
 * have a range of +-8K for 8-bit data, +-128K for 12-bit data.  This 
 * convention improves accuracy in integer implementations and saves some 
 * work in floating-point ones. 
 * Quantization of the output coefficients is done by jcdctmgr.c. 
 */ 
 
#if BITS_IN_JSAMPLE == 8 
typedef int DCTELEM;		/* 16 or 32 bits is fine */ 
#else 
typedef INT32 DCTELEM;		/* must have 32 bits */ 
#endif 
 
typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data)); 
typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data)); 
 
 
/* 
 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer 
 * to an output sample array.  The routine must dequantize the input data as 
 * well as perform the IDCT; for dequantization, it uses the multiplier table 
 * pointed to by compptr->dct_table.  The output data is to be placed into the 
 * sample array starting at a specified column.  (Any row offset needed will 
 * be applied to the array pointer before it is passed to the IDCT code.) 
 * Note that the number of samples emitted by the IDCT routine is 
 * DCT_scaled_size * DCT_scaled_size. 
 */ 
 
/* typedef inverse_DCT_method_ptr is declared in jpegint.h */ 
 
/* 
 * Each IDCT routine has its own ideas about the best dct_table element type. 
 */ 
 
typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */ 
#if BITS_IN_JSAMPLE == 8 
typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */ 
#define IFAST_SCALE_BITS  2	/* fractional bits in scale factors */ 
#else 
typedef INT32 IFAST_MULT_TYPE;	/* need 32 bits for scaled quantizers */ 
#define IFAST_SCALE_BITS  13	/* fractional bits in scale factors */ 
#endif 
typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */ 
 
 
/* 
 * Each IDCT routine is responsible for range-limiting its results and 
 * converting them to unsigned form (0..MAXJSAMPLE).  The raw outputs could 
 * be quite far out of range if the input data is corrupt, so a bulletproof 
 * range-limiting step is required.  We use a mask-and-table-lookup method 
 * to do the combined operations quickly.  See the comments with 
 * prepare_range_limit_table (in jdmaster.c) for more info. 
 */ 
 
#define IDCT_range_limit(cinfo)  ((cinfo)->sample_range_limit + CENTERJSAMPLE) 
 
#define RANGE_MASK  (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */ 
 
 
 
/* Extern declarations for the forward and inverse DCT routines. */ 
 
EXTERN(void) jpeg_fdct_islow JPP((DCTELEM * data)); 
EXTERN(void) jpeg_fdct_ifast JPP((DCTELEM * data)); 
EXTERN(void) jpeg_fdct_float JPP((FAST_FLOAT * data)); 
 
EXTERN(void) jpeg_idct_islow 
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 
EXTERN(void) jpeg_idct_ifast 
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 
EXTERN(void) jpeg_idct_float 
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 
EXTERN(void) jpeg_idct_4x4 
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 
EXTERN(void) jpeg_idct_2x2 
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 
EXTERN(void) jpeg_idct_1x1 
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); 
 
 
/* 
 * Macros for handling fixed-point arithmetic; these are used by many 
 * but not all of the DCT/IDCT modules. 
 * 
 * All values are expected to be of type INT32. 
 * Fractional constants are scaled left by CONST_BITS bits. 
 * CONST_BITS is defined within each module using these macros, 
 * and may differ from one module to the next. 
 */ 
 
#define ONE	((INT32) 1) 
#define CONST_SCALE (ONE << CONST_BITS) 
 
/* Convert a positive real constant to an integer scaled by CONST_SCALE. 
 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time, 
 * thus causing a lot of useless floating-point operations at run time. 
 */ 
 
#define FIX(x)	((INT32) ((x) * CONST_SCALE + 0.5)) 
 
/* Descale and correctly round an INT32 value that's scaled by N bits. 
 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding 
 * the fudge factor is correct for either sign of X. 
 */ 
 
#define DESCALE(x,n)  RIGHT_SHIFT((x) + (ONE << ((n)-1)), n) 
 
/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. 
 * This macro is used only when the two inputs will actually be no more than 
 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a 
 * full 32x32 multiply.  This provides a useful speedup on many machines. 
 * Unfortunately there is no way to specify a 16x16->32 multiply portably 
 * in C, but some C compilers will do the right thing if you provide the 
 * correct combination of casts. 
 */ 
 
#ifdef SHORTxSHORT_32		/* may work if 'int' is 32 bits */ 
#define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT16) (const))) 
#endif 
#ifdef SHORTxLCONST_32		/* known to work with Microsoft C 6.0 */ 
#define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT32) (const))) 
#endif 
 
#ifndef MULTIPLY16C16		/* default definition */ 
#define MULTIPLY16C16(var,const)  ((var) * (const)) 
#endif 
 
/* Same except both inputs are variables. */ 
 
#ifdef SHORTxSHORT_32		/* may work if 'int' is 32 bits */ 
#define MULTIPLY16V16(var1,var2)  (((INT16) (var1)) * ((INT16) (var2))) 
#endif 
 
#ifndef MULTIPLY16V16		/* default definition */ 
#define MULTIPLY16V16(var1,var2)  ((var1) * (var2)) 
#endif