/* * 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 == 8typedef int DCTELEM;		/* 16 or 32 bits is fine */#elsetypedef INT32 DCTELEM;		/* must have 32 bits */#endiftypedef 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 INT32 ISLOW_MULT_TYPE; /* short or int, whichever is faster */#if BITS_IN_JSAMPLE == 8typedef INT16 IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */#define IFAST_SCALE_BITS  2	/* fractional bits in scale factors */#elsetypedef INT32 IFAST_MULT_TYPE;	/* need 32 bits for scaled quantizers */#define IFAST_SCALE_BITS  13	/* fractional bits in scale factors */#endiftypedef 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