OLD | NEW |
(Empty) | |
| 1 /* |
| 2 * jdct.h |
| 3 * |
| 4 * Copyright (C) 1994-1996, Thomas G. Lane. |
| 5 * This file is part of the Independent JPEG Group's software. |
| 6 * For conditions of distribution and use, see the accompanying README file. |
| 7 * |
| 8 * This include file contains common declarations for the forward and |
| 9 * inverse DCT modules. These declarations are private to the DCT managers |
| 10 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms. |
| 11 * The individual DCT algorithms are kept in separate files to ease |
| 12 * machine-dependent tuning (e.g., assembly coding). |
| 13 */ |
| 14 |
| 15 |
| 16 /* |
| 17 * A forward DCT routine is given a pointer to a work area of type DCTELEM[]; |
| 18 * the DCT is to be performed in-place in that buffer. Type DCTELEM is int |
| 19 * for 8-bit samples, INT32 for 12-bit samples. (NOTE: Floating-point DCT |
| 20 * implementations use an array of type FAST_FLOAT, instead.) |
| 21 * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE). |
| 22 * The DCT outputs are returned scaled up by a factor of 8; they therefore |
| 23 * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This |
| 24 * convention improves accuracy in integer implementations and saves some |
| 25 * work in floating-point ones. |
| 26 * Quantization of the output coefficients is done by jcdctmgr.c. This |
| 27 * step requires an unsigned type and also one with twice the bits. |
| 28 */ |
| 29 |
| 30 #if BITS_IN_JSAMPLE == 8 |
| 31 #ifndef WITH_SIMD |
| 32 typedef int DCTELEM; /* 16 or 32 bits is fine */ |
| 33 typedef unsigned int UDCTELEM; |
| 34 typedef unsigned long long UDCTELEM2; |
| 35 #else |
| 36 typedef short DCTELEM; /* prefer 16 bit with SIMD for parellelism */ |
| 37 typedef unsigned short UDCTELEM; |
| 38 typedef unsigned int UDCTELEM2; |
| 39 #endif |
| 40 #else |
| 41 typedef INT32 DCTELEM; /* must have 32 bits */ |
| 42 typedef UINT32 UDCTELEM; |
| 43 typedef unsigned long long UDCTELEM2; |
| 44 #endif |
| 45 |
| 46 |
| 47 /* |
| 48 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer |
| 49 * to an output sample array. The routine must dequantize the input data as |
| 50 * well as perform the IDCT; for dequantization, it uses the multiplier table |
| 51 * pointed to by compptr->dct_table. The output data is to be placed into the |
| 52 * sample array starting at a specified column. (Any row offset needed will |
| 53 * be applied to the array pointer before it is passed to the IDCT code.) |
| 54 * Note that the number of samples emitted by the IDCT routine is |
| 55 * DCT_scaled_size * DCT_scaled_size. |
| 56 */ |
| 57 |
| 58 /* typedef inverse_DCT_method_ptr is declared in jpegint.h */ |
| 59 |
| 60 /* |
| 61 * Each IDCT routine has its own ideas about the best dct_table element type. |
| 62 */ |
| 63 |
| 64 typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */ |
| 65 #if BITS_IN_JSAMPLE == 8 |
| 66 typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */ |
| 67 #define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */ |
| 68 #else |
| 69 typedef INT32 IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */ |
| 70 #define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */ |
| 71 #endif |
| 72 typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */ |
| 73 |
| 74 |
| 75 /* |
| 76 * Each IDCT routine is responsible for range-limiting its results and |
| 77 * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could |
| 78 * be quite far out of range if the input data is corrupt, so a bulletproof |
| 79 * range-limiting step is required. We use a mask-and-table-lookup method |
| 80 * to do the combined operations quickly. See the comments with |
| 81 * prepare_range_limit_table (in jdmaster.c) for more info. |
| 82 */ |
| 83 |
| 84 #define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit + CENTERJSAMPLE) |
| 85 |
| 86 #define RANGE_MASK (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */ |
| 87 |
| 88 |
| 89 /* Short forms of external names for systems with brain-damaged linkers. */ |
| 90 |
| 91 #ifdef NEED_SHORT_EXTERNAL_NAMES |
| 92 #define jpeg_fdct_islow jFDislow |
| 93 #define jpeg_fdct_ifast jFDifast |
| 94 #define jpeg_fdct_float jFDfloat |
| 95 #define jpeg_idct_islow jRDislow |
| 96 #define jpeg_idct_ifast jRDifast |
| 97 #define jpeg_idct_float jRDfloat |
| 98 #define jpeg_idct_4x4 jRD4x4 |
| 99 #define jpeg_idct_2x2 jRD2x2 |
| 100 #define jpeg_idct_1x1 jRD1x1 |
| 101 #endif /* NEED_SHORT_EXTERNAL_NAMES */ |
| 102 |
| 103 /* Extern declarations for the forward and inverse DCT routines. */ |
| 104 |
| 105 EXTERN(void) jpeg_fdct_islow JPP((DCTELEM * data)); |
| 106 EXTERN(void) jpeg_fdct_ifast JPP((DCTELEM * data)); |
| 107 EXTERN(void) jpeg_fdct_float JPP((FAST_FLOAT * data)); |
| 108 |
| 109 EXTERN(void) jpeg_idct_islow |
| 110 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, |
| 111 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); |
| 112 EXTERN(void) jpeg_idct_ifast |
| 113 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, |
| 114 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); |
| 115 EXTERN(void) jpeg_idct_float |
| 116 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, |
| 117 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); |
| 118 EXTERN(void) jpeg_idct_4x4 |
| 119 JPP((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 JPP((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 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr, |
| 126 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)); |
| 127 |
| 128 |
| 129 /* |
| 130 * Macros for handling fixed-point arithmetic; these are used by many |
| 131 * but not all of the DCT/IDCT modules. |
| 132 * |
| 133 * All values are expected to be of type INT32. |
| 134 * Fractional constants are scaled left by CONST_BITS bits. |
| 135 * CONST_BITS is defined within each module using these macros, |
| 136 * and may differ from one module to the next. |
| 137 */ |
| 138 |
| 139 #define ONE ((INT32) 1) |
| 140 #define CONST_SCALE (ONE << CONST_BITS) |
| 141 |
| 142 /* Convert a positive real constant to an integer scaled by CONST_SCALE. |
| 143 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time, |
| 144 * thus causing a lot of useless floating-point operations at run time. |
| 145 */ |
| 146 |
| 147 #define FIX(x) ((INT32) ((x) * CONST_SCALE + 0.5)) |
| 148 |
| 149 /* Descale and correctly round an INT32 value that's scaled by N bits. |
| 150 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding |
| 151 * the fudge factor is correct for either sign of X. |
| 152 */ |
| 153 |
| 154 #define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n) |
| 155 |
| 156 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. |
| 157 * This macro is used only when the two inputs will actually be no more than |
| 158 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a |
| 159 * full 32x32 multiply. This provides a useful speedup on many machines. |
| 160 * Unfortunately there is no way to specify a 16x16->32 multiply portably |
| 161 * in C, but some C compilers will do the right thing if you provide the |
| 162 * correct combination of casts. |
| 163 */ |
| 164 |
| 165 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ |
| 166 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const))) |
| 167 #endif |
| 168 #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ |
| 169 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT32) (const))) |
| 170 #endif |
| 171 |
| 172 #ifndef MULTIPLY16C16 /* default definition */ |
| 173 #define MULTIPLY16C16(var,const) ((var) * (const)) |
| 174 #endif |
| 175 |
| 176 /* Same except both inputs are variables. */ |
| 177 |
| 178 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ |
| 179 #define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2))) |
| 180 #endif |
| 181 |
| 182 #ifndef MULTIPLY16V16 /* default definition */ |
| 183 #define MULTIPLY16V16(var1,var2) ((var1) * (var2)) |
| 184 #endif |
OLD | NEW |