/* * jdct.h * * This file was part of the Independent JPEG Group's software: * Copyright (C) 1994-1996, Thomas G. Lane. * libjpeg-turbo Modifications: * Copyright (C) 2015, D. R. Commander. * For conditions of distribution and use, see the accompanying README.ijg * 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, JLONG 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. This * step requires an unsigned type and also one with twice the bits. */ #if BITS_IN_JSAMPLE == 8 #ifndef WITH_SIMD typedef int DCTELEM; /* 16 or 32 bits is fine */ typedef unsigned int UDCTELEM; typedef unsigned long long UDCTELEM2; #else DCTELEM; /* prefer 16 bit with SIMD for parellelism */ UDCTELEM; UDCTELEM2; #endif #else typedef JLONG DCTELEM; /* must have 32 bits */ typedef unsigned long long UDCTELEM2; #endif /* * 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. */ ISLOW_MULT_TYPE; /* short or int, whichever is faster */ #if BITS_IN_JSAMPLE == 8 IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */ #define IFAST_SCALE_BITS … #else typedef JLONG IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */ #define IFAST_SCALE_BITS … #endif 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) … #define RANGE_MASK … /* Extern declarations for the forward and inverse DCT routines. */ EXTERN(void) jpeg_fdct_islow(DCTELEM *data); EXTERN(void) jpeg_fdct_ifast(DCTELEM *data); EXTERN(void) jpeg_fdct_float(FAST_FLOAT *data); EXTERN(void) jpeg_idct_islow(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_ifast(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_float(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_7x7(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_6x6(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_5x5(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_4x4(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_3x3(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_2x2(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_1x1(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_9x9(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_10x10(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_11x11(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_12x12(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_13x13(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_14x14(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_15x15(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); EXTERN(void) jpeg_idct_16x16(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 JLONG. * 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 … #define CONST_SCALE … /* 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) … /* Descale and correctly round a JLONG 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) … /* Multiply a JLONG variable by a JLONG constant to yield a JLONG 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 … #endif #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ #define MULTIPLY16C16 … #endif #ifndef MULTIPLY16C16 /* default definition */ #define MULTIPLY16C16(var, const) … #endif /* Same except both inputs are variables. */ #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ #define MULTIPLY16V16 … #endif #ifndef MULTIPLY16V16 /* default definition */ #define MULTIPLY16V16(var1, var2) … #endif
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