1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/libs/libjpeg/jidctfst.c	Thu Sep 08 06:28:38 2011 +0300
     1.3 @@ -0,0 +1,368 @@
     1.4 +/*
     1.5 + * jidctfst.c
     1.6 + *
     1.7 + * Copyright (C) 1994-1998, Thomas G. Lane.
     1.8 + * This file is part of the Independent JPEG Group's software.
     1.9 + * For conditions of distribution and use, see the accompanying README file.
    1.10 + *
    1.11 + * This file contains a fast, not so accurate integer implementation of the
    1.12 + * inverse DCT (Discrete Cosine Transform).  In the IJG code, this routine
    1.13 + * must also perform dequantization of the input coefficients.
    1.14 + *
    1.15 + * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
    1.16 + * on each row (or vice versa, but it's more convenient to emit a row at
    1.17 + * a time).  Direct algorithms are also available, but they are much more
    1.18 + * complex and seem not to be any faster when reduced to code.
    1.19 + *
    1.20 + * This implementation is based on Arai, Agui, and Nakajima's algorithm for
    1.21 + * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
    1.22 + * Japanese, but the algorithm is described in the Pennebaker & Mitchell
    1.23 + * JPEG textbook (see REFERENCES section in file README).  The following code
    1.24 + * is based directly on figure 4-8 in P&M.
    1.25 + * While an 8-point DCT cannot be done in less than 11 multiplies, it is
    1.26 + * possible to arrange the computation so that many of the multiplies are
    1.27 + * simple scalings of the final outputs.  These multiplies can then be
    1.28 + * folded into the multiplications or divisions by the JPEG quantization
    1.29 + * table entries.  The AA&N method leaves only 5 multiplies and 29 adds
    1.30 + * to be done in the DCT itself.
    1.31 + * The primary disadvantage of this method is that with fixed-point math,
    1.32 + * accuracy is lost due to imprecise representation of the scaled
    1.33 + * quantization values.  The smaller the quantization table entry, the less
    1.34 + * precise the scaled value, so this implementation does worse with high-
    1.35 + * quality-setting files than with low-quality ones.
    1.36 + */
    1.37 +
    1.38 +#define JPEG_INTERNALS
    1.39 +#include "jinclude.h"
    1.40 +#include "jpeglib.h"
    1.41 +#include "jdct.h"		/* Private declarations for DCT subsystem */
    1.42 +
    1.43 +#ifdef DCT_IFAST_SUPPORTED
    1.44 +
    1.45 +
    1.46 +/*
    1.47 + * This module is specialized to the case DCTSIZE = 8.
    1.48 + */
    1.49 +
    1.50 +#if DCTSIZE != 8
    1.51 +  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
    1.52 +#endif
    1.53 +
    1.54 +
    1.55 +/* Scaling decisions are generally the same as in the LL&M algorithm;
    1.56 + * see jidctint.c for more details.  However, we choose to descale
    1.57 + * (right shift) multiplication products as soon as they are formed,
    1.58 + * rather than carrying additional fractional bits into subsequent additions.
    1.59 + * This compromises accuracy slightly, but it lets us save a few shifts.
    1.60 + * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
    1.61 + * everywhere except in the multiplications proper; this saves a good deal
    1.62 + * of work on 16-bit-int machines.
    1.63 + *
    1.64 + * The dequantized coefficients are not integers because the AA&N scaling
    1.65 + * factors have been incorporated.  We represent them scaled up by PASS1_BITS,
    1.66 + * so that the first and second IDCT rounds have the same input scaling.
    1.67 + * For 8-bit JSAMPLEs, we choose IFAST_SCALE_BITS = PASS1_BITS so as to
    1.68 + * avoid a descaling shift; this compromises accuracy rather drastically
    1.69 + * for small quantization table entries, but it saves a lot of shifts.
    1.70 + * For 12-bit JSAMPLEs, there's no hope of using 16x16 multiplies anyway,
    1.71 + * so we use a much larger scaling factor to preserve accuracy.
    1.72 + *
    1.73 + * A final compromise is to represent the multiplicative constants to only
    1.74 + * 8 fractional bits, rather than 13.  This saves some shifting work on some
    1.75 + * machines, and may also reduce the cost of multiplication (since there
    1.76 + * are fewer one-bits in the constants).
    1.77 + */
    1.78 +
    1.79 +#if BITS_IN_JSAMPLE == 8
    1.80 +#define CONST_BITS  8
    1.81 +#define PASS1_BITS  2
    1.82 +#else
    1.83 +#define CONST_BITS  8
    1.84 +#define PASS1_BITS  1		/* lose a little precision to avoid overflow */
    1.85 +#endif
    1.86 +
    1.87 +/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
    1.88 + * causing a lot of useless floating-point operations at run time.
    1.89 + * To get around this we use the following pre-calculated constants.
    1.90 + * If you change CONST_BITS you may want to add appropriate values.
    1.91 + * (With a reasonable C compiler, you can just rely on the FIX() macro...)
    1.92 + */
    1.93 +
    1.94 +#if CONST_BITS == 8
    1.95 +#define FIX_1_082392200  ((INT32)  277)		/* FIX(1.082392200) */
    1.96 +#define FIX_1_414213562  ((INT32)  362)		/* FIX(1.414213562) */
    1.97 +#define FIX_1_847759065  ((INT32)  473)		/* FIX(1.847759065) */
    1.98 +#define FIX_2_613125930  ((INT32)  669)		/* FIX(2.613125930) */
    1.99 +#else
   1.100 +#define FIX_1_082392200  FIX(1.082392200)
   1.101 +#define FIX_1_414213562  FIX(1.414213562)
   1.102 +#define FIX_1_847759065  FIX(1.847759065)
   1.103 +#define FIX_2_613125930  FIX(2.613125930)
   1.104 +#endif
   1.105 +
   1.106 +
   1.107 +/* We can gain a little more speed, with a further compromise in accuracy,
   1.108 + * by omitting the addition in a descaling shift.  This yields an incorrectly
   1.109 + * rounded result half the time...
   1.110 + */
   1.111 +
   1.112 +#ifndef USE_ACCURATE_ROUNDING
   1.113 +#undef DESCALE
   1.114 +#define DESCALE(x,n)  RIGHT_SHIFT(x, n)
   1.115 +#endif
   1.116 +
   1.117 +
   1.118 +/* Multiply a DCTELEM variable by an INT32 constant, and immediately
   1.119 + * descale to yield a DCTELEM result.
   1.120 + */
   1.121 +
   1.122 +#define MULTIPLY(var,const)  ((DCTELEM) DESCALE((var) * (const), CONST_BITS))
   1.123 +
   1.124 +
   1.125 +/* Dequantize a coefficient by multiplying it by the multiplier-table
   1.126 + * entry; produce a DCTELEM result.  For 8-bit data a 16x16->16
   1.127 + * multiplication will do.  For 12-bit data, the multiplier table is
   1.128 + * declared INT32, so a 32-bit multiply will be used.
   1.129 + */
   1.130 +
   1.131 +#if BITS_IN_JSAMPLE == 8
   1.132 +#define DEQUANTIZE(coef,quantval)  (((IFAST_MULT_TYPE) (coef)) * (quantval))
   1.133 +#else
   1.134 +#define DEQUANTIZE(coef,quantval)  \
   1.135 +	DESCALE((coef)*(quantval), IFAST_SCALE_BITS-PASS1_BITS)
   1.136 +#endif
   1.137 +
   1.138 +
   1.139 +/* Like DESCALE, but applies to a DCTELEM and produces an int.
   1.140 + * We assume that int right shift is unsigned if INT32 right shift is.
   1.141 + */
   1.142 +
   1.143 +#ifdef RIGHT_SHIFT_IS_UNSIGNED
   1.144 +#define ISHIFT_TEMPS	DCTELEM ishift_temp;
   1.145 +#if BITS_IN_JSAMPLE == 8
   1.146 +#define DCTELEMBITS  16		/* DCTELEM may be 16 or 32 bits */
   1.147 +#else
   1.148 +#define DCTELEMBITS  32		/* DCTELEM must be 32 bits */
   1.149 +#endif
   1.150 +#define IRIGHT_SHIFT(x,shft)  \
   1.151 +    ((ishift_temp = (x)) < 0 ? \
   1.152 +     (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \
   1.153 +     (ishift_temp >> (shft)))
   1.154 +#else
   1.155 +#define ISHIFT_TEMPS
   1.156 +#define IRIGHT_SHIFT(x,shft)	((x) >> (shft))
   1.157 +#endif
   1.158 +
   1.159 +#ifdef USE_ACCURATE_ROUNDING
   1.160 +#define IDESCALE(x,n)  ((int) IRIGHT_SHIFT((x) + (1 << ((n)-1)), n))
   1.161 +#else
   1.162 +#define IDESCALE(x,n)  ((int) IRIGHT_SHIFT(x, n))
   1.163 +#endif
   1.164 +
   1.165 +
   1.166 +/*
   1.167 + * Perform dequantization and inverse DCT on one block of coefficients.
   1.168 + */
   1.169 +
   1.170 +GLOBAL(void)
   1.171 +jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
   1.172 +		 JCOEFPTR coef_block,
   1.173 +		 JSAMPARRAY output_buf, JDIMENSION output_col)
   1.174 +{
   1.175 +  DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
   1.176 +  DCTELEM tmp10, tmp11, tmp12, tmp13;
   1.177 +  DCTELEM z5, z10, z11, z12, z13;
   1.178 +  JCOEFPTR inptr;
   1.179 +  IFAST_MULT_TYPE * quantptr;
   1.180 +  int * wsptr;
   1.181 +  JSAMPROW outptr;
   1.182 +  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   1.183 +  int ctr;
   1.184 +  int workspace[DCTSIZE2];	/* buffers data between passes */
   1.185 +  SHIFT_TEMPS			/* for DESCALE */
   1.186 +  ISHIFT_TEMPS			/* for IDESCALE */
   1.187 +
   1.188 +  /* Pass 1: process columns from input, store into work array. */
   1.189 +
   1.190 +  inptr = coef_block;
   1.191 +  quantptr = (IFAST_MULT_TYPE *) compptr->dct_table;
   1.192 +  wsptr = workspace;
   1.193 +  for (ctr = DCTSIZE; ctr > 0; ctr--) {
   1.194 +    /* Due to quantization, we will usually find that many of the input
   1.195 +     * coefficients are zero, especially the AC terms.  We can exploit this
   1.196 +     * by short-circuiting the IDCT calculation for any column in which all
   1.197 +     * the AC terms are zero.  In that case each output is equal to the
   1.198 +     * DC coefficient (with scale factor as needed).
   1.199 +     * With typical images and quantization tables, half or more of the
   1.200 +     * column DCT calculations can be simplified this way.
   1.201 +     */
   1.202 +    
   1.203 +    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
   1.204 +	inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
   1.205 +	inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
   1.206 +	inptr[DCTSIZE*7] == 0) {
   1.207 +      /* AC terms all zero */
   1.208 +      int dcval = (int) DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
   1.209 +
   1.210 +      wsptr[DCTSIZE*0] = dcval;
   1.211 +      wsptr[DCTSIZE*1] = dcval;
   1.212 +      wsptr[DCTSIZE*2] = dcval;
   1.213 +      wsptr[DCTSIZE*3] = dcval;
   1.214 +      wsptr[DCTSIZE*4] = dcval;
   1.215 +      wsptr[DCTSIZE*5] = dcval;
   1.216 +      wsptr[DCTSIZE*6] = dcval;
   1.217 +      wsptr[DCTSIZE*7] = dcval;
   1.218 +      
   1.219 +      inptr++;			/* advance pointers to next column */
   1.220 +      quantptr++;
   1.221 +      wsptr++;
   1.222 +      continue;
   1.223 +    }
   1.224 +    
   1.225 +    /* Even part */
   1.226 +
   1.227 +    tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
   1.228 +    tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
   1.229 +    tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
   1.230 +    tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
   1.231 +
   1.232 +    tmp10 = tmp0 + tmp2;	/* phase 3 */
   1.233 +    tmp11 = tmp0 - tmp2;
   1.234 +
   1.235 +    tmp13 = tmp1 + tmp3;	/* phases 5-3 */
   1.236 +    tmp12 = MULTIPLY(tmp1 - tmp3, FIX_1_414213562) - tmp13; /* 2*c4 */
   1.237 +
   1.238 +    tmp0 = tmp10 + tmp13;	/* phase 2 */
   1.239 +    tmp3 = tmp10 - tmp13;
   1.240 +    tmp1 = tmp11 + tmp12;
   1.241 +    tmp2 = tmp11 - tmp12;
   1.242 +    
   1.243 +    /* Odd part */
   1.244 +
   1.245 +    tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
   1.246 +    tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
   1.247 +    tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
   1.248 +    tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
   1.249 +
   1.250 +    z13 = tmp6 + tmp5;		/* phase 6 */
   1.251 +    z10 = tmp6 - tmp5;
   1.252 +    z11 = tmp4 + tmp7;
   1.253 +    z12 = tmp4 - tmp7;
   1.254 +
   1.255 +    tmp7 = z11 + z13;		/* phase 5 */
   1.256 +    tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
   1.257 +
   1.258 +    z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
   1.259 +    tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
   1.260 +    tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
   1.261 +
   1.262 +    tmp6 = tmp12 - tmp7;	/* phase 2 */
   1.263 +    tmp5 = tmp11 - tmp6;
   1.264 +    tmp4 = tmp10 + tmp5;
   1.265 +
   1.266 +    wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7);
   1.267 +    wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7);
   1.268 +    wsptr[DCTSIZE*1] = (int) (tmp1 + tmp6);
   1.269 +    wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6);
   1.270 +    wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5);
   1.271 +    wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5);
   1.272 +    wsptr[DCTSIZE*4] = (int) (tmp3 + tmp4);
   1.273 +    wsptr[DCTSIZE*3] = (int) (tmp3 - tmp4);
   1.274 +
   1.275 +    inptr++;			/* advance pointers to next column */
   1.276 +    quantptr++;
   1.277 +    wsptr++;
   1.278 +  }
   1.279 +  
   1.280 +  /* Pass 2: process rows from work array, store into output array. */
   1.281 +  /* Note that we must descale the results by a factor of 8 == 2**3, */
   1.282 +  /* and also undo the PASS1_BITS scaling. */
   1.283 +
   1.284 +  wsptr = workspace;
   1.285 +  for (ctr = 0; ctr < DCTSIZE; ctr++) {
   1.286 +    outptr = output_buf[ctr] + output_col;
   1.287 +    /* Rows of zeroes can be exploited in the same way as we did with columns.
   1.288 +     * However, the column calculation has created many nonzero AC terms, so
   1.289 +     * the simplification applies less often (typically 5% to 10% of the time).
   1.290 +     * On machines with very fast multiplication, it's possible that the
   1.291 +     * test takes more time than it's worth.  In that case this section
   1.292 +     * may be commented out.
   1.293 +     */
   1.294 +    
   1.295 +#ifndef NO_ZERO_ROW_TEST
   1.296 +    if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
   1.297 +	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
   1.298 +      /* AC terms all zero */
   1.299 +      JSAMPLE dcval = range_limit[IDESCALE(wsptr[0], PASS1_BITS+3)
   1.300 +				  & RANGE_MASK];
   1.301 +      
   1.302 +      outptr[0] = dcval;
   1.303 +      outptr[1] = dcval;
   1.304 +      outptr[2] = dcval;
   1.305 +      outptr[3] = dcval;
   1.306 +      outptr[4] = dcval;
   1.307 +      outptr[5] = dcval;
   1.308 +      outptr[6] = dcval;
   1.309 +      outptr[7] = dcval;
   1.310 +
   1.311 +      wsptr += DCTSIZE;		/* advance pointer to next row */
   1.312 +      continue;
   1.313 +    }
   1.314 +#endif
   1.315 +    
   1.316 +    /* Even part */
   1.317 +
   1.318 +    tmp10 = ((DCTELEM) wsptr[0] + (DCTELEM) wsptr[4]);
   1.319 +    tmp11 = ((DCTELEM) wsptr[0] - (DCTELEM) wsptr[4]);
   1.320 +
   1.321 +    tmp13 = ((DCTELEM) wsptr[2] + (DCTELEM) wsptr[6]);
   1.322 +    tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6], FIX_1_414213562)
   1.323 +	    - tmp13;
   1.324 +
   1.325 +    tmp0 = tmp10 + tmp13;
   1.326 +    tmp3 = tmp10 - tmp13;
   1.327 +    tmp1 = tmp11 + tmp12;
   1.328 +    tmp2 = tmp11 - tmp12;
   1.329 +
   1.330 +    /* Odd part */
   1.331 +
   1.332 +    z13 = (DCTELEM) wsptr[5] + (DCTELEM) wsptr[3];
   1.333 +    z10 = (DCTELEM) wsptr[5] - (DCTELEM) wsptr[3];
   1.334 +    z11 = (DCTELEM) wsptr[1] + (DCTELEM) wsptr[7];
   1.335 +    z12 = (DCTELEM) wsptr[1] - (DCTELEM) wsptr[7];
   1.336 +
   1.337 +    tmp7 = z11 + z13;		/* phase 5 */
   1.338 +    tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
   1.339 +
   1.340 +    z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
   1.341 +    tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
   1.342 +    tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
   1.343 +
   1.344 +    tmp6 = tmp12 - tmp7;	/* phase 2 */
   1.345 +    tmp5 = tmp11 - tmp6;
   1.346 +    tmp4 = tmp10 + tmp5;
   1.347 +
   1.348 +    /* Final output stage: scale down by a factor of 8 and range-limit */
   1.349 +
   1.350 +    outptr[0] = range_limit[IDESCALE(tmp0 + tmp7, PASS1_BITS+3)
   1.351 +			    & RANGE_MASK];
   1.352 +    outptr[7] = range_limit[IDESCALE(tmp0 - tmp7, PASS1_BITS+3)
   1.353 +			    & RANGE_MASK];
   1.354 +    outptr[1] = range_limit[IDESCALE(tmp1 + tmp6, PASS1_BITS+3)
   1.355 +			    & RANGE_MASK];
   1.356 +    outptr[6] = range_limit[IDESCALE(tmp1 - tmp6, PASS1_BITS+3)
   1.357 +			    & RANGE_MASK];
   1.358 +    outptr[2] = range_limit[IDESCALE(tmp2 + tmp5, PASS1_BITS+3)
   1.359 +			    & RANGE_MASK];
   1.360 +    outptr[5] = range_limit[IDESCALE(tmp2 - tmp5, PASS1_BITS+3)
   1.361 +			    & RANGE_MASK];
   1.362 +    outptr[4] = range_limit[IDESCALE(tmp3 + tmp4, PASS1_BITS+3)
   1.363 +			    & RANGE_MASK];
   1.364 +    outptr[3] = range_limit[IDESCALE(tmp3 - tmp4, PASS1_BITS+3)
   1.365 +			    & RANGE_MASK];
   1.366 +
   1.367 +    wsptr += DCTSIZE;		/* advance pointer to next row */
   1.368 +  }
   1.369 +}
   1.370 +
   1.371 +#endif /* DCT_IFAST_SUPPORTED */