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modules/javafx.graphics/src/main/native-iio/libjpeg7/jfdctfst.c

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   1 /*
   2  * jfdctfst.c
   3  *
   4  * Copyright (C) 1994-1996, Thomas G. Lane.
   5  * Modified 2003-2009 by Guido Vollbeding.
   6  * This file is part of the Independent JPEG Group's software.
   7  * For conditions of distribution and use, see the accompanying README file.
   8  *
   9  * This file contains a fast, not so accurate integer implementation of the
  10  * forward DCT (Discrete Cosine Transform).
  11  *
  12  * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
  13  * on each column.  Direct algorithms are also available, but they are
  14  * much more complex and seem not to be any faster when reduced to code.
  15  *
  16  * This implementation is based on Arai, Agui, and Nakajima's algorithm for
  17  * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
  18  * Japanese, but the algorithm is described in the Pennebaker & Mitchell
  19  * JPEG textbook (see REFERENCES section in file README).  The following code
  20  * is based directly on figure 4-8 in P&M.
  21  * While an 8-point DCT cannot be done in less than 11 multiplies, it is
  22  * possible to arrange the computation so that many of the multiplies are
  23  * simple scalings of the final outputs.  These multiplies can then be
  24  * folded into the multiplications or divisions by the JPEG quantization
  25  * table entries.  The AA&N method leaves only 5 multiplies and 29 adds


  27  * The primary disadvantage of this method is that with fixed-point math,
  28  * accuracy is lost due to imprecise representation of the scaled
  29  * quantization values.  The smaller the quantization table entry, the less
  30  * precise the scaled value, so this implementation does worse with high-
  31  * quality-setting files than with low-quality ones.
  32  */
  33 
  34 #define JPEG_INTERNALS
  35 #include "jinclude.h"
  36 #include "jpeglib.h"
  37 #include "jdct.h"               /* Private declarations for DCT subsystem */
  38 
  39 #ifdef DCT_IFAST_SUPPORTED
  40 
  41 
  42 /*
  43  * This module is specialized to the case DCTSIZE = 8.
  44  */
  45 
  46 #if DCTSIZE != 8
  47   Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
  48 #endif
  49 
  50 
  51 /* Scaling decisions are generally the same as in the LL&M algorithm;
  52  * see jfdctint.c for more details.  However, we choose to descale
  53  * (right shift) multiplication products as soon as they are formed,
  54  * rather than carrying additional fractional bits into subsequent additions.
  55  * This compromises accuracy slightly, but it lets us save a few shifts.
  56  * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
  57  * everywhere except in the multiplications proper; this saves a good deal
  58  * of work on 16-bit-int machines.
  59  *
  60  * Again to save a few shifts, the intermediate results between pass 1 and
  61  * pass 2 are not upscaled, but are represented only to integral precision.
  62  *
  63  * A final compromise is to represent the multiplicative constants to only
  64  * 8 fractional bits, rather than 13.  This saves some shifting work on some
  65  * machines, and may also reduce the cost of multiplication (since there
  66  * are fewer one-bits in the constants).
  67  */


  92 /* We can gain a little more speed, with a further compromise in accuracy,
  93  * by omitting the addition in a descaling shift.  This yields an incorrectly
  94  * rounded result half the time...
  95  */
  96 
  97 #ifndef USE_ACCURATE_ROUNDING
  98 #undef DESCALE
  99 #define DESCALE(x,n)  RIGHT_SHIFT(x, n)
 100 #endif
 101 
 102 
 103 /* Multiply a DCTELEM variable by an INT32 constant, and immediately
 104  * descale to yield a DCTELEM result.
 105  */
 106 
 107 #define MULTIPLY(var,const)  ((DCTELEM) DESCALE((var) * (const), CONST_BITS))
 108 
 109 
 110 /*
 111  * Perform the forward DCT on one block of samples.


 112  */
 113 
 114 GLOBAL(void)
 115 jpeg_fdct_ifast (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
 116 {
 117   DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
 118   DCTELEM tmp10, tmp11, tmp12, tmp13;
 119   DCTELEM z1, z2, z3, z4, z5, z11, z13;
 120   DCTELEM *dataptr;
 121   JSAMPROW elemptr;
 122   int ctr;
 123   SHIFT_TEMPS
 124 
 125   /* Pass 1: process rows. */
 126 
 127   dataptr = data;
 128   for (ctr = 0; ctr < DCTSIZE; ctr++) {
 129     elemptr = sample_data[ctr] + start_col;
 130 
 131     /* Load data into workspace */
 132     tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]);
 133     tmp7 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]);
 134     tmp1 = GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]);
 135     tmp6 = GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]);
 136     tmp2 = GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]);
 137     tmp5 = GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]);
 138     tmp3 = GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]);
 139     tmp4 = GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[4]);
 140 
 141     /* Even part */
 142 
 143     tmp10 = tmp0 + tmp3;        /* phase 2 */
 144     tmp13 = tmp0 - tmp3;
 145     tmp11 = tmp1 + tmp2;
 146     tmp12 = tmp1 - tmp2;
 147 
 148     /* Apply unsigned->signed conversion */
 149     dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
 150     dataptr[4] = tmp10 - tmp11;
 151 
 152     z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
 153     dataptr[2] = tmp13 + z1;    /* phase 5 */
 154     dataptr[6] = tmp13 - z1;
 155 
 156     /* Odd part */
 157 
 158     tmp10 = tmp4 + tmp5;        /* phase 2 */
 159     tmp11 = tmp5 + tmp6;
 160     tmp12 = tmp6 + tmp7;
 161 
 162     /* The rotator is modified from fig 4-8 to avoid extra negations. */
 163     z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
 164     z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
 165     z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
 166     z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */
 167 
 168     z11 = tmp7 + z3;            /* phase 5 */


   1 /*
   2  * jfdctfst.c
   3  *
   4  * Copyright (C) 1994-1996, Thomas G. Lane.
   5  * Modified 2003-2017 by Guido Vollbeding.
   6  * This file is part of the Independent JPEG Group's software.
   7  * For conditions of distribution and use, see the accompanying README file.
   8  *
   9  * This file contains a fast, not so accurate integer implementation of the
  10  * forward DCT (Discrete Cosine Transform).
  11  *
  12  * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
  13  * on each column.  Direct algorithms are also available, but they are
  14  * much more complex and seem not to be any faster when reduced to code.
  15  *
  16  * This implementation is based on Arai, Agui, and Nakajima's algorithm for
  17  * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
  18  * Japanese, but the algorithm is described in the Pennebaker & Mitchell
  19  * JPEG textbook (see REFERENCES section in file README).  The following code
  20  * is based directly on figure 4-8 in P&M.
  21  * While an 8-point DCT cannot be done in less than 11 multiplies, it is
  22  * possible to arrange the computation so that many of the multiplies are
  23  * simple scalings of the final outputs.  These multiplies can then be
  24  * folded into the multiplications or divisions by the JPEG quantization
  25  * table entries.  The AA&N method leaves only 5 multiplies and 29 adds


  27  * The primary disadvantage of this method is that with fixed-point math,
  28  * accuracy is lost due to imprecise representation of the scaled
  29  * quantization values.  The smaller the quantization table entry, the less
  30  * precise the scaled value, so this implementation does worse with high-
  31  * quality-setting files than with low-quality ones.
  32  */
  33 
  34 #define JPEG_INTERNALS
  35 #include "jinclude.h"
  36 #include "jpeglib.h"
  37 #include "jdct.h"               /* Private declarations for DCT subsystem */
  38 
  39 #ifdef DCT_IFAST_SUPPORTED
  40 
  41 
  42 /*
  43  * This module is specialized to the case DCTSIZE = 8.
  44  */
  45 
  46 #if DCTSIZE != 8
  47   Sorry, this code only copes with 8x8 DCT blocks. /* deliberate syntax err */
  48 #endif
  49 
  50 
  51 /* Scaling decisions are generally the same as in the LL&M algorithm;
  52  * see jfdctint.c for more details.  However, we choose to descale
  53  * (right shift) multiplication products as soon as they are formed,
  54  * rather than carrying additional fractional bits into subsequent additions.
  55  * This compromises accuracy slightly, but it lets us save a few shifts.
  56  * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
  57  * everywhere except in the multiplications proper; this saves a good deal
  58  * of work on 16-bit-int machines.
  59  *
  60  * Again to save a few shifts, the intermediate results between pass 1 and
  61  * pass 2 are not upscaled, but are represented only to integral precision.
  62  *
  63  * A final compromise is to represent the multiplicative constants to only
  64  * 8 fractional bits, rather than 13.  This saves some shifting work on some
  65  * machines, and may also reduce the cost of multiplication (since there
  66  * are fewer one-bits in the constants).
  67  */


  92 /* We can gain a little more speed, with a further compromise in accuracy,
  93  * by omitting the addition in a descaling shift.  This yields an incorrectly
  94  * rounded result half the time...
  95  */
  96 
  97 #ifndef USE_ACCURATE_ROUNDING
  98 #undef DESCALE
  99 #define DESCALE(x,n)  RIGHT_SHIFT(x, n)
 100 #endif
 101 
 102 
 103 /* Multiply a DCTELEM variable by an INT32 constant, and immediately
 104  * descale to yield a DCTELEM result.
 105  */
 106 
 107 #define MULTIPLY(var,const)  ((DCTELEM) DESCALE((var) * (const), CONST_BITS))
 108 
 109 
 110 /*
 111  * Perform the forward DCT on one block of samples.
 112  *
 113  * cK represents cos(K*pi/16).
 114  */
 115 
 116 GLOBAL(void)
 117 jpeg_fdct_ifast (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
 118 {
 119   DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
 120   DCTELEM tmp10, tmp11, tmp12, tmp13;
 121   DCTELEM z1, z2, z3, z4, z5, z11, z13;
 122   DCTELEM *dataptr;
 123   JSAMPROW elemptr;
 124   int ctr;
 125   SHIFT_TEMPS
 126 
 127   /* Pass 1: process rows. */
 128 
 129   dataptr = data;
 130   for (ctr = 0; ctr < DCTSIZE; ctr++) {
 131     elemptr = sample_data[ctr] + start_col;
 132 
 133     /* Load data into workspace */
 134     tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]);
 135     tmp7 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]);
 136     tmp1 = GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]);
 137     tmp6 = GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]);
 138     tmp2 = GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]);
 139     tmp5 = GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]);
 140     tmp3 = GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]);
 141     tmp4 = GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[4]);
 142 
 143     /* Even part */
 144 
 145     tmp10 = tmp0 + tmp3;        /* phase 2 */
 146     tmp13 = tmp0 - tmp3;
 147     tmp11 = tmp1 + tmp2;
 148     tmp12 = tmp1 - tmp2;
 149 
 150     /* Apply unsigned->signed conversion. */
 151     dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
 152     dataptr[4] = tmp10 - tmp11;
 153 
 154     z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
 155     dataptr[2] = tmp13 + z1;    /* phase 5 */
 156     dataptr[6] = tmp13 - z1;
 157 
 158     /* Odd part */
 159 
 160     tmp10 = tmp4 + tmp5;        /* phase 2 */
 161     tmp11 = tmp5 + tmp6;
 162     tmp12 = tmp6 + tmp7;
 163 
 164     /* The rotator is modified from fig 4-8 to avoid extra negations. */
 165     z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
 166     z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
 167     z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
 168     z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */
 169 
 170     z11 = tmp7 + z3;            /* phase 5 */


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