jdct.h (10135B)
1 /* 2 * jdct.h 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1994-1996, Thomas G. Lane. 6 * libjpeg-turbo Modifications: 7 * Copyright (C) 2015, 2022, D. R. Commander. 8 * For conditions of distribution and use, see the accompanying README.ijg 9 * file. 10 * 11 * This include file contains common declarations for the forward and 12 * inverse DCT modules. These declarations are private to the DCT managers 13 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms. 14 * The individual DCT algorithms are kept in separate files to ease 15 * machine-dependent tuning (e.g., assembly coding). 16 */ 17 18 #include "jsamplecomp.h" 19 20 21 /* 22 * A forward DCT routine is given a pointer to a work area of type DCTELEM[]; 23 * the DCT is to be performed in-place in that buffer. Type DCTELEM is int 24 * for 8-bit samples, JLONG for 12-bit samples. (NOTE: Floating-point DCT 25 * implementations use an array of type FAST_FLOAT, instead.) 26 * The DCT inputs are expected to be signed (range +-_CENTERJSAMPLE). 27 * The DCT outputs are returned scaled up by a factor of 8; they therefore 28 * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This 29 * convention improves accuracy in integer implementations and saves some 30 * work in floating-point ones. 31 * Quantization of the output coefficients is done by jcdctmgr.c. This 32 * step requires an unsigned type and also one with twice the bits. 33 */ 34 35 #if BITS_IN_JSAMPLE == 8 36 #ifndef WITH_SIMD 37 typedef int DCTELEM; /* 16 or 32 bits is fine */ 38 typedef unsigned int UDCTELEM; 39 typedef unsigned long long UDCTELEM2; 40 #else 41 typedef short DCTELEM; /* prefer 16 bit with SIMD for parellelism */ 42 typedef unsigned short UDCTELEM; 43 typedef unsigned int UDCTELEM2; 44 #endif 45 #else 46 typedef JLONG DCTELEM; /* must have 32 bits */ 47 typedef unsigned long long UDCTELEM2; 48 #endif 49 50 51 /* 52 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer 53 * to an output sample array. The routine must dequantize the input data as 54 * well as perform the IDCT; for dequantization, it uses the multiplier table 55 * pointed to by compptr->dct_table. The output data is to be placed into the 56 * sample array starting at a specified column. (Any row offset needed will 57 * be applied to the array pointer before it is passed to the IDCT code.) 58 * Note that the number of samples emitted by the IDCT routine is 59 * DCT_scaled_size * DCT_scaled_size. 60 */ 61 62 /* typedef inverse_DCT_method_ptr is declared in jpegint.h */ 63 64 /* 65 * Each IDCT routine has its own ideas about the best dct_table element type. 66 */ 67 68 typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */ 69 #if BITS_IN_JSAMPLE == 8 70 typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */ 71 #define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */ 72 #else 73 typedef JLONG IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */ 74 #define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */ 75 #endif 76 typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */ 77 78 79 /* 80 * Each IDCT routine is responsible for range-limiting its results and 81 * converting them to unsigned form (0.._MAXJSAMPLE). The raw outputs could 82 * be quite far out of range if the input data is corrupt, so a bulletproof 83 * range-limiting step is required. We use a mask-and-table-lookup method 84 * to do the combined operations quickly. See the comments with 85 * prepare_range_limit_table (in jdmaster.c) for more info. 86 */ 87 88 #define IDCT_range_limit(cinfo) \ 89 ((_JSAMPLE *)((cinfo)->sample_range_limit) + _CENTERJSAMPLE) 90 91 #define RANGE_MASK (_MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */ 92 93 94 /* Extern declarations for the forward and inverse DCT routines. */ 95 96 EXTERN(void) _jpeg_fdct_islow(DCTELEM *data); 97 EXTERN(void) _jpeg_fdct_ifast(DCTELEM *data); 98 EXTERN(void) jpeg_fdct_float(FAST_FLOAT *data); 99 100 EXTERN(void) _jpeg_idct_islow(j_decompress_ptr cinfo, 101 jpeg_component_info *compptr, 102 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 103 JDIMENSION output_col); 104 EXTERN(void) _jpeg_idct_ifast(j_decompress_ptr cinfo, 105 jpeg_component_info *compptr, 106 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 107 JDIMENSION output_col); 108 EXTERN(void) _jpeg_idct_float(j_decompress_ptr cinfo, 109 jpeg_component_info *compptr, 110 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 111 JDIMENSION output_col); 112 EXTERN(void) _jpeg_idct_7x7(j_decompress_ptr cinfo, 113 jpeg_component_info *compptr, JCOEFPTR coef_block, 114 _JSAMPARRAY output_buf, JDIMENSION output_col); 115 EXTERN(void) _jpeg_idct_6x6(j_decompress_ptr cinfo, 116 jpeg_component_info *compptr, JCOEFPTR coef_block, 117 _JSAMPARRAY output_buf, JDIMENSION output_col); 118 EXTERN(void) _jpeg_idct_5x5(j_decompress_ptr cinfo, 119 jpeg_component_info *compptr, JCOEFPTR coef_block, 120 _JSAMPARRAY output_buf, JDIMENSION output_col); 121 EXTERN(void) _jpeg_idct_4x4(j_decompress_ptr cinfo, 122 jpeg_component_info *compptr, JCOEFPTR coef_block, 123 _JSAMPARRAY output_buf, JDIMENSION output_col); 124 EXTERN(void) _jpeg_idct_3x3(j_decompress_ptr cinfo, 125 jpeg_component_info *compptr, JCOEFPTR coef_block, 126 _JSAMPARRAY output_buf, JDIMENSION output_col); 127 EXTERN(void) _jpeg_idct_2x2(j_decompress_ptr cinfo, 128 jpeg_component_info *compptr, JCOEFPTR coef_block, 129 _JSAMPARRAY output_buf, JDIMENSION output_col); 130 EXTERN(void) _jpeg_idct_1x1(j_decompress_ptr cinfo, 131 jpeg_component_info *compptr, JCOEFPTR coef_block, 132 _JSAMPARRAY output_buf, JDIMENSION output_col); 133 EXTERN(void) _jpeg_idct_9x9(j_decompress_ptr cinfo, 134 jpeg_component_info *compptr, JCOEFPTR coef_block, 135 _JSAMPARRAY output_buf, JDIMENSION output_col); 136 EXTERN(void) _jpeg_idct_10x10(j_decompress_ptr cinfo, 137 jpeg_component_info *compptr, 138 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 139 JDIMENSION output_col); 140 EXTERN(void) _jpeg_idct_11x11(j_decompress_ptr cinfo, 141 jpeg_component_info *compptr, 142 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 143 JDIMENSION output_col); 144 EXTERN(void) _jpeg_idct_12x12(j_decompress_ptr cinfo, 145 jpeg_component_info *compptr, 146 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 147 JDIMENSION output_col); 148 EXTERN(void) _jpeg_idct_13x13(j_decompress_ptr cinfo, 149 jpeg_component_info *compptr, 150 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 151 JDIMENSION output_col); 152 EXTERN(void) _jpeg_idct_14x14(j_decompress_ptr cinfo, 153 jpeg_component_info *compptr, 154 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 155 JDIMENSION output_col); 156 EXTERN(void) _jpeg_idct_15x15(j_decompress_ptr cinfo, 157 jpeg_component_info *compptr, 158 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 159 JDIMENSION output_col); 160 EXTERN(void) _jpeg_idct_16x16(j_decompress_ptr cinfo, 161 jpeg_component_info *compptr, 162 JCOEFPTR coef_block, _JSAMPARRAY output_buf, 163 JDIMENSION output_col); 164 165 166 /* 167 * Macros for handling fixed-point arithmetic; these are used by many 168 * but not all of the DCT/IDCT modules. 169 * 170 * All values are expected to be of type JLONG. 171 * Fractional constants are scaled left by CONST_BITS bits. 172 * CONST_BITS is defined within each module using these macros, 173 * and may differ from one module to the next. 174 */ 175 176 #define ONE ((JLONG)1) 177 #define CONST_SCALE (ONE << CONST_BITS) 178 179 /* Convert a positive real constant to an integer scaled by CONST_SCALE. 180 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time, 181 * thus causing a lot of useless floating-point operations at run time. 182 */ 183 184 #define FIX(x) ((JLONG)((x) * CONST_SCALE + 0.5)) 185 186 /* Descale and correctly round a JLONG value that's scaled by N bits. 187 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding 188 * the fudge factor is correct for either sign of X. 189 */ 190 191 #define DESCALE(x, n) RIGHT_SHIFT((x) + (ONE << ((n) - 1)), n) 192 193 /* Multiply a JLONG variable by a JLONG constant to yield a JLONG result. 194 * This macro is used only when the two inputs will actually be no more than 195 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a 196 * full 32x32 multiply. This provides a useful speedup on many machines. 197 * Unfortunately there is no way to specify a 16x16->32 multiply portably 198 * in C, but some C compilers will do the right thing if you provide the 199 * correct combination of casts. 200 */ 201 202 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ 203 #define MULTIPLY16C16(var, const) (((INT16)(var)) * ((INT16)(const))) 204 #endif 205 #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ 206 #define MULTIPLY16C16(var, const) (((INT16)(var)) * ((JLONG)(const))) 207 #endif 208 209 #ifndef MULTIPLY16C16 /* default definition */ 210 #define MULTIPLY16C16(var, const) ((var) * (const)) 211 #endif 212 213 /* Same except both inputs are variables. */ 214 215 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ 216 #define MULTIPLY16V16(var1, var2) (((INT16)(var1)) * ((INT16)(var2))) 217 #endif 218 219 #ifndef MULTIPLY16V16 /* default definition */ 220 #define MULTIPLY16V16(var1, var2) ((var1) * (var2)) 221 #endif