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, 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 19 /* 20 * A forward DCT routine is given a pointer to a work area of type DCTELEM[]; 21 * the DCT is to be performed in-place in that buffer. Type DCTELEM is int 22 * for 8-bit samples, JLONG for 12-bit samples. (NOTE: Floating-point DCT 23 * implementations use an array of type FAST_FLOAT, instead.) 24 * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE). 25 * The DCT outputs are returned scaled up by a factor of 8; they therefore 26 * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This 27 * convention improves accuracy in integer implementations and saves some 28 * work in floating-point ones. 29 * Quantization of the output coefficients is done by jcdctmgr.c. This 30 * step requires an unsigned type and also one with twice the bits. 31 */ 32 33 #if BITS_IN_JSAMPLE == 8 34 #ifndef WITH_SIMD 35 typedef int DCTELEM; /* 16 or 32 bits is fine */ 36 typedef unsigned int UDCTELEM; 37 typedef unsigned long long UDCTELEM2; 38 #else 39 typedef short DCTELEM; /* prefer 16 bit with SIMD for parellelism */ 40 typedef unsigned short UDCTELEM; 41 typedef unsigned int UDCTELEM2; 42 #endif 43 #else 44 typedef JLONG DCTELEM; /* must have 32 bits */ 45 typedef unsigned long long UDCTELEM2; 46 #endif 47 48 49 /* 50 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer 51 * to an output sample array. The routine must dequantize the input data as 52 * well as perform the IDCT; for dequantization, it uses the multiplier table 53 * pointed to by compptr->dct_table. The output data is to be placed into the 54 * sample array starting at a specified column. (Any row offset needed will 55 * be applied to the array pointer before it is passed to the IDCT code.) 56 * Note that the number of samples emitted by the IDCT routine is 57 * DCT_scaled_size * DCT_scaled_size. 58 */ 59 60 /* typedef inverse_DCT_method_ptr is declared in jpegint.h */ 61 62 /* 63 * Each IDCT routine has its own ideas about the best dct_table element type. 64 */ 65 66 typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */ 67 #if BITS_IN_JSAMPLE == 8 68 typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */ 69 #define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */ 70 #else 71 typedef JLONG IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */ 72 #define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */ 73 #endif 74 typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */ 75 76 77 /* 78 * Each IDCT routine is responsible for range-limiting its results and 79 * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could 80 * be quite far out of range if the input data is corrupt, so a bulletproof 81 * range-limiting step is required. We use a mask-and-table-lookup method 82 * to do the combined operations quickly. See the comments with 83 * prepare_range_limit_table (in jdmaster.c) for more info. 84 */ 85 86 #define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit + CENTERJSAMPLE) 87 88 #define RANGE_MASK (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */ 89 90 91 /* Extern declarations for the forward and inverse DCT routines. */ 92 93 EXTERN(void) jpeg_fdct_islow (DCTELEM *data); 94 EXTERN(void) jpeg_fdct_ifast (DCTELEM *data); 95 EXTERN(void) jpeg_fdct_float (FAST_FLOAT *data); 96 97 EXTERN(void) jpeg_idct_islow 98 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 99 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 100 EXTERN(void) jpeg_idct_ifast 101 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 102 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 103 EXTERN(void) jpeg_idct_float 104 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 105 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 106 EXTERN(void) jpeg_idct_7x7 107 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 108 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 109 EXTERN(void) jpeg_idct_6x6 110 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 111 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 112 EXTERN(void) jpeg_idct_5x5 113 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 114 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 115 EXTERN(void) jpeg_idct_4x4 116 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 117 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 118 EXTERN(void) jpeg_idct_3x3 119 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 120 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 121 EXTERN(void) jpeg_idct_2x2 122 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 123 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 124 EXTERN(void) jpeg_idct_1x1 125 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 126 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 127 EXTERN(void) jpeg_idct_9x9 128 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 129 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 130 EXTERN(void) jpeg_idct_10x10 131 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 132 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 133 EXTERN(void) jpeg_idct_11x11 134 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 135 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 136 EXTERN(void) jpeg_idct_12x12 137 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 138 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 139 EXTERN(void) jpeg_idct_13x13 140 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 141 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 142 EXTERN(void) jpeg_idct_14x14 143 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 144 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 145 EXTERN(void) jpeg_idct_15x15 146 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 147 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 148 EXTERN(void) jpeg_idct_16x16 149 (j_decompress_ptr cinfo, jpeg_component_info *compptr, 150 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col); 151 152 153 /* 154 * Macros for handling fixed-point arithmetic; these are used by many 155 * but not all of the DCT/IDCT modules. 156 * 157 * All values are expected to be of type JLONG. 158 * Fractional constants are scaled left by CONST_BITS bits. 159 * CONST_BITS is defined within each module using these macros, 160 * and may differ from one module to the next. 161 */ 162 163 #define ONE ((JLONG) 1) 164 #define CONST_SCALE (ONE << CONST_BITS) 165 166 /* Convert a positive real constant to an integer scaled by CONST_SCALE. 167 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time, 168 * thus causing a lot of useless floating-point operations at run time. 169 */ 170 171 #define FIX(x) ((JLONG) ((x) * CONST_SCALE + 0.5)) 172 173 /* Descale and correctly round a JLONG value that's scaled by N bits. 174 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding 175 * the fudge factor is correct for either sign of X. 176 */ 177 178 #define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n) 179 180 /* Multiply a JLONG variable by a JLONG constant to yield a JLONG result. 181 * This macro is used only when the two inputs will actually be no more than 182 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a 183 * full 32x32 multiply. This provides a useful speedup on many machines. 184 * Unfortunately there is no way to specify a 16x16->32 multiply portably 185 * in C, but some C compilers will do the right thing if you provide the 186 * correct combination of casts. 187 */ 188 189 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ 190 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const))) 191 #endif 192 #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ 193 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((JLONG) (const))) 194 #endif 195 196 #ifndef MULTIPLY16C16 /* default definition */ 197 #define MULTIPLY16C16(var,const) ((var) * (const)) 198 #endif 199 200 /* Same except both inputs are variables. */ 201 202 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ 203 #define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2))) 204 #endif 205 206 #ifndef MULTIPLY16V16 /* default definition */ 207 #define MULTIPLY16V16(var1,var2) ((var1) * (var2)) 208 #endif 209
