/* * jdct.h * * Copyright (C) 1994, 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 */ /* Short forms of external names for systems with brain-damaged linkers. */ #ifdef NEED_SHORT_EXTERNAL_NAMES #define jpeg_fdct_islow jFDislow #define jpeg_fdct_ifast jFDifast #define jpeg_fdct_float jFDfloat #define jpeg_idct_islow jRDislow #define jpeg_idct_ifast jRDifast #define jpeg_idct_float jRDfloat #define jpeg_idct_4x4 jRD4x4 #define jpeg_idct_2x2 jRD2x2 #define jpeg_idct_1x1 jRD1x1 #endif /* NEED_SHORT_EXTERNAL_NAMES */ /* 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