nuclear@26: /* nuclear@26: * jdct.h nuclear@26: * nuclear@26: * Copyright (C) 1994-1996, Thomas G. Lane. nuclear@26: * This file is part of the Independent JPEG Group's software. nuclear@26: * For conditions of distribution and use, see the accompanying README file. nuclear@26: * nuclear@26: * This include file contains common declarations for the forward and nuclear@26: * inverse DCT modules. These declarations are private to the DCT managers nuclear@26: * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms. nuclear@26: * The individual DCT algorithms are kept in separate files to ease nuclear@26: * machine-dependent tuning (e.g., assembly coding). nuclear@26: */ nuclear@26: nuclear@26: nuclear@26: /* nuclear@26: * A forward DCT routine is given a pointer to a work area of type DCTELEM[]; nuclear@26: * the DCT is to be performed in-place in that buffer. Type DCTELEM is int nuclear@26: * for 8-bit samples, INT32 for 12-bit samples. (NOTE: Floating-point DCT nuclear@26: * implementations use an array of type FAST_FLOAT, instead.) nuclear@26: * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE). nuclear@26: * The DCT outputs are returned scaled up by a factor of 8; they therefore nuclear@26: * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This nuclear@26: * convention improves accuracy in integer implementations and saves some nuclear@26: * work in floating-point ones. nuclear@26: * Quantization of the output coefficients is done by jcdctmgr.c. nuclear@26: */ nuclear@26: nuclear@26: #if BITS_IN_JSAMPLE == 8 nuclear@26: typedef int DCTELEM; /* 16 or 32 bits is fine */ nuclear@26: #else nuclear@26: typedef INT32 DCTELEM; /* must have 32 bits */ nuclear@26: #endif nuclear@26: nuclear@26: typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data)); nuclear@26: typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data)); nuclear@26: nuclear@26: nuclear@26: /* nuclear@26: * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer nuclear@26: * to an output sample array. The routine must dequantize the input data as nuclear@26: * well as perform the IDCT; for dequantization, it uses the multiplier table nuclear@26: * pointed to by compptr->dct_table. The output data is to be placed into the nuclear@26: * sample array starting at a specified column. (Any row offset needed will nuclear@26: * be applied to the array pointer before it is passed to the IDCT code.) nuclear@26: * Note that the number of samples emitted by the IDCT routine is nuclear@26: * DCT_scaled_size * DCT_scaled_size. nuclear@26: */ nuclear@26: nuclear@26: /* typedef inverse_DCT_method_ptr is declared in jpegint.h */ nuclear@26: nuclear@26: /* nuclear@26: * Each IDCT routine has its own ideas about the best dct_table element type. nuclear@26: */ nuclear@26: nuclear@26: typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */ nuclear@26: #if BITS_IN_JSAMPLE == 8 nuclear@26: typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */ nuclear@26: #define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */ nuclear@26: #else nuclear@26: typedef INT32 IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */ nuclear@26: #define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */ nuclear@26: #endif nuclear@26: typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */ nuclear@26: nuclear@26: nuclear@26: /* nuclear@26: * Each IDCT routine is responsible for range-limiting its results and nuclear@26: * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could nuclear@26: * be quite far out of range if the input data is corrupt, so a bulletproof nuclear@26: * range-limiting step is required. We use a mask-and-table-lookup method nuclear@26: * to do the combined operations quickly. See the comments with nuclear@26: * prepare_range_limit_table (in jdmaster.c) for more info. nuclear@26: */ nuclear@26: nuclear@26: #define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit + CENTERJSAMPLE) nuclear@26: nuclear@26: #define RANGE_MASK (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */ nuclear@26: nuclear@26: nuclear@26: /* Short forms of external names for systems with brain-damaged linkers. */ nuclear@26: nuclear@26: #ifdef NEED_SHORT_EXTERNAL_NAMES nuclear@26: #define jpeg_fdct_islow jFDislow nuclear@26: #define jpeg_fdct_ifast jFDifast nuclear@26: #define jpeg_fdct_float jFDfloat nuclear@26: #define jpeg_idct_islow jRDislow nuclear@26: #define jpeg_idct_ifast jRDifast nuclear@26: #define jpeg_idct_float jRDfloat nuclear@26: #define jpeg_idct_4x4 jRD4x4 nuclear@26: #define jpeg_idct_2x2 jRD2x2 nuclear@26: #define jpeg_idct_1x1 jRD1x1 nuclear@26: #endif /* NEED_SHORT_EXTERNAL_NAMES */ nuclear@26: nuclear@26: /* Extern declarations for the forward and inverse DCT routines. */ nuclear@26: nuclear@26: EXTERN(void) jpeg_fdct_islow JPP((DCTELEM * data)); nuclear@26: EXTERN(void) jpeg_fdct_ifast JPP((DCTELEM * data)); nuclear@26: EXTERN(void) jpeg_fdct_float JPP((FAST_FLOAT * data)); nuclear@26: nuclear@26: EXTERN(void) jpeg_idct_islow nuclear@26: JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, nuclear@26: JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); nuclear@26: EXTERN(void) jpeg_idct_ifast nuclear@26: JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, nuclear@26: JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); nuclear@26: EXTERN(void) jpeg_idct_float nuclear@26: JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, nuclear@26: JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); nuclear@26: EXTERN(void) jpeg_idct_4x4 nuclear@26: JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, nuclear@26: JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); nuclear@26: EXTERN(void) jpeg_idct_2x2 nuclear@26: JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, nuclear@26: JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); nuclear@26: EXTERN(void) jpeg_idct_1x1 nuclear@26: JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, nuclear@26: JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); nuclear@26: nuclear@26: nuclear@26: /* nuclear@26: * Macros for handling fixed-point arithmetic; these are used by many nuclear@26: * but not all of the DCT/IDCT modules. nuclear@26: * nuclear@26: * All values are expected to be of type INT32. nuclear@26: * Fractional constants are scaled left by CONST_BITS bits. nuclear@26: * CONST_BITS is defined within each module using these macros, nuclear@26: * and may differ from one module to the next. nuclear@26: */ nuclear@26: nuclear@26: #define ONE ((INT32) 1) nuclear@26: #define CONST_SCALE (ONE << CONST_BITS) nuclear@26: nuclear@26: /* Convert a positive real constant to an integer scaled by CONST_SCALE. nuclear@26: * Caution: some C compilers fail to reduce "FIX(constant)" at compile time, nuclear@26: * thus causing a lot of useless floating-point operations at run time. nuclear@26: */ nuclear@26: nuclear@26: #define FIX(x) ((INT32) ((x) * CONST_SCALE + 0.5)) nuclear@26: nuclear@26: /* Descale and correctly round an INT32 value that's scaled by N bits. nuclear@26: * We assume RIGHT_SHIFT rounds towards minus infinity, so adding nuclear@26: * the fudge factor is correct for either sign of X. nuclear@26: */ nuclear@26: nuclear@26: #define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n) nuclear@26: nuclear@26: /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. nuclear@26: * This macro is used only when the two inputs will actually be no more than nuclear@26: * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a nuclear@26: * full 32x32 multiply. This provides a useful speedup on many machines. nuclear@26: * Unfortunately there is no way to specify a 16x16->32 multiply portably nuclear@26: * in C, but some C compilers will do the right thing if you provide the nuclear@26: * correct combination of casts. nuclear@26: */ nuclear@26: nuclear@26: #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ nuclear@26: #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const))) nuclear@26: #endif nuclear@26: #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ nuclear@26: #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT32) (const))) nuclear@26: #endif nuclear@26: nuclear@26: #ifndef MULTIPLY16C16 /* default definition */ nuclear@26: #define MULTIPLY16C16(var,const) ((var) * (const)) nuclear@26: #endif nuclear@26: nuclear@26: /* Same except both inputs are variables. */ nuclear@26: nuclear@26: #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ nuclear@26: #define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2))) nuclear@26: #endif nuclear@26: nuclear@26: #ifndef MULTIPLY16V16 /* default definition */ nuclear@26: #define MULTIPLY16V16(var1,var2) ((var1) * (var2)) nuclear@26: #endif