media/libjpeg/jdct.h

   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_7x7           jRD7x7
  99 #define jpeg_idct_6x6           jRD6x6
 100 #define jpeg_idct_5x5           jRD5x5
 101 #define jpeg_idct_4x4           jRD4x4
 102 #define jpeg_idct_3x3           jRD3x3
 103 #define jpeg_idct_2x2           jRD2x2
 104 #define jpeg_idct_1x1           jRD1x1
 105 #define jpeg_idct_9x9           jRD9x9
 106 #define jpeg_idct_10x10         jRD10x10
 107 #define jpeg_idct_11x11         jRD11x11
 108 #define jpeg_idct_12x12         jRD12x12
 109 #define jpeg_idct_13x13         jRD13x13
 110 #define jpeg_idct_14x14         jRD14x14
 111 #define jpeg_idct_15x15         jRD15x15
 112 #define jpeg_idct_16x16         jRD16x16
 113 #endif /* NEED_SHORT_EXTERNAL_NAMES */
 114
 115 /* Extern declarations for the forward and inverse DCT routines. */
 116
 117 EXTERN(void) jpeg_fdct_islow JPP((DCTELEM * data));
 118 EXTERN(void) jpeg_fdct_ifast JPP((DCTELEM * data));
 119 EXTERN(void) jpeg_fdct_float JPP((FAST_FLOAT * data));
 120
 121 EXTERN(void) jpeg_idct_islow
 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_ifast
 125     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 126          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 127 EXTERN(void) jpeg_idct_float
 128     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 129          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 130 EXTERN(void) jpeg_idct_7x7
 131     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 132          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 133 EXTERN(void) jpeg_idct_6x6
 134     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 135          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 136 EXTERN(void) jpeg_idct_5x5
 137     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 138          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 139 EXTERN(void) jpeg_idct_4x4
 140     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 141          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 142 EXTERN(void) jpeg_idct_3x3
 143     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 144          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 145 EXTERN(void) jpeg_idct_2x2
 146     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 147          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 148 EXTERN(void) jpeg_idct_1x1
 149     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 150          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 151 EXTERN(void) jpeg_idct_9x9
 152     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 153          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 154 EXTERN(void) jpeg_idct_10x10
 155     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 156          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 157 EXTERN(void) jpeg_idct_11x11
 158     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 159          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 160 EXTERN(void) jpeg_idct_12x12
 161     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 162          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 163 EXTERN(void) jpeg_idct_13x13
 164     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 165          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 166 EXTERN(void) jpeg_idct_14x14
 167     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 168          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 169 EXTERN(void) jpeg_idct_15x15
 170     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 171          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 172 EXTERN(void) jpeg_idct_16x16
 173     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 174          JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 175
 176
 177 /*
 178  * Macros for handling fixed-point arithmetic; these are used by many
 179  * but not all of the DCT/IDCT modules.
 180  *
 181  * All values are expected to be of type INT32.
 182  * Fractional constants are scaled left by CONST_BITS bits.
 183  * CONST_BITS is defined within each module using these macros,
 184  * and may differ from one module to the next.
 185  */
 186
 187 #define ONE     ((INT32) 1)
 188 #define CONST_SCALE (ONE << CONST_BITS)
 189
 190 /* Convert a positive real constant to an integer scaled by CONST_SCALE.
 191  * Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
 192  * thus causing a lot of useless floating-point operations at run time.
 193  */
 194
 195 #define FIX(x)  ((INT32) ((x) * CONST_SCALE + 0.5))
 196
 197 /* Descale and correctly round an INT32 value that's scaled by N bits.
 198  * We assume RIGHT_SHIFT rounds towards minus infinity, so adding
 199  * the fudge factor is correct for either sign of X.
 200  */
 201
 202 #define DESCALE(x,n)  RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)
 203
 204 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
 205  * This macro is used only when the two inputs will actually be no more than
 206  * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a
 207  * full 32x32 multiply.  This provides a useful speedup on many machines.
 208  * Unfortunately there is no way to specify a 16x16->32 multiply portably
 209  * in C, but some C compilers will do the right thing if you provide the
 210  * correct combination of casts.
 211  */
 212
 213 #ifdef SHORTxSHORT_32           /* may work if 'int' is 32 bits */
 214 #define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT16) (const)))
 215 #endif
 216 #ifdef SHORTxLCONST_32          /* known to work with Microsoft C 6.0 */
 217 #define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT32) (const)))
 218 #endif
 219
 220 #ifndef MULTIPLY16C16           /* default definition */
 221 #define MULTIPLY16C16(var,const)  ((var) * (const))
 222 #endif
 223
 224 /* Same except both inputs are variables. */
 225
 226 #ifdef SHORTxSHORT_32           /* may work if 'int' is 32 bits */
 227 #define MULTIPLY16V16(var1,var2)  (((INT16) (var1)) * ((INT16) (var2)))
 228 #endif
 229
 230 #ifndef MULTIPLY16V16           /* default definition */
 231 #define MULTIPLY16V16(var1,var2)  ((var1) * (var2))
 232 #endif