547 lines
20 KiB
C++
547 lines
20 KiB
C++
//$T Jidctint.c GC! 1.097 02/16/01 13:42:10
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// * jidctint.c Copyright (C) 1991-1994, Thomas G. Lane. This file is part of the
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// * Independent JPEG Group's software. For conditions of distribution and use, see
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// * the accompanying README file. This file contains a slow-but-accurate integer
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// * implementation of the inverse DCT (Discrete Cosine Transform). In the IJG code,
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// * this routine must also perform dequantization of the input coefficients. A 2-D
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// * IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT on each row
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// * (or vice versa, but it's more convenient to emit a row at a time). Direct
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// * algorithms are also available, but they are much more complex and seem not to
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// * be any faster when reduced to code. This implementation is based on an
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// * algorithm described in C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical
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// * Fast 1-D DCT Algorithms with 11 Multiplications", Proc. Int'l. Conf. on
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// * Acoustics, Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991. The
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// * primary algorithm described there uses 11 multiplies and 29 adds. We use their
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// * alternate method with 12 multiplies and 32 adds. The advantage of this method
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// * is that no data path contains more than one multiplication; this allows a very
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// * simple and accurate implementation in scaled fixed-point arithmetic, with a
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// * minimal number of shifts.
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#define JPEG_INTERNALS
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#include "JINCLUDE.h"
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#include "JPEGLIB.h"
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#include "JDCT.h" // Private declarations for DCT subsystem
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#ifdef DCT_ISLOW_SUPPORTED
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// This module is specialized to the case DCTSIZE = 8.
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#if DCTSIZE != 8
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Sorry, this code only copes with 8 x8 DCTs. // deliberate syntax err
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#endif
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// * The poop on this scaling stuff is as follows: Each 1-D IDCT step produces
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// * outputs which are a factor of sqrt(N) larger than the true IDCT outputs. The
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// * final outputs are therefore a factor of N larger than desired; since N=8 this
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// * can be cured by a simple right shift at the end of the algorithm. The advantage
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// * of this arrangement is that we save two multiplications per 1-D IDCT, because
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// * the y0 and y4 inputs need not be divided by sqrt(N). We have to do addition and
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// * subtraction of the integer inputs, which is no problem, and multiplication by
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// * fractional constants, which is a problem to do in integer arithmetic. We
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// * multiply all the constants by CONST_SCALE and convert them to integer constants
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// * (thus retaining CONST_BITS bits of precision in the constants). After doing a
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// * multiplication we have to divide the product by CONST_SCALE, with proper
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// * rounding, to produce the correct output. This division can be done cheaply as a
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// * right shift of CONST_BITS bits. We postpone shifting as long as possible so
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// * that partial sums can be added together with full fractional precision. The
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// * outputs of the first pass are scaled up by PASS1_BITS bits so that they are
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// * represented to better-than-integral precision. These outputs require
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// * BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word with the
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// * recommended scaling. (To scale up 12-bit sample data further, an intermediate
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// * INT32 array would be needed.) To avoid overflow of the 32-bit intermediate
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// * results in pass 2, we must have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <=
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// * 26. Error analysis shows that the values given below are the most effective.
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#if BITS_IN_JSAMPLE == 8
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#define CONST_BITS 13
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#define PASS1_BITS 2
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#else
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#define CONST_BITS 13
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#define PASS1_BITS 1 // lose a little precision to avoid overflow
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#endif
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// * Some C compilers fail to reduce "FIX(constant)" at compile time, thus causing a
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// * lot of useless floating-point operations at run time. To get around this we use
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// * the following pre-calculated constants. If you change CONST_BITS you may want
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// * to add appropriate values. (With a reasonable C compiler, you can just rely on
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// * the FIX() macro...)
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#if CONST_BITS == 13
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#define FIX_0_298631336 ((INT32) 2446) // FIX(0.298631336)
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#define FIX_0_390180644 ((INT32) 3196) // FIX(0.390180644)
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#define FIX_0_541196100 ((INT32) 4433) // FIX(0.541196100)
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#define FIX_0_765366865 ((INT32) 6270) // FIX(0.765366865)
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#define FIX_0_899976223 ((INT32) 7373) // FIX(0.899976223)
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#define FIX_1_175875602 ((INT32) 9633) // FIX(1.175875602)
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#define FIX_1_501321110 ((INT32) 12299) // FIX(1.501321110)
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#define FIX_1_847759065 ((INT32) 15137) // FIX(1.847759065)
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#define FIX_1_961570560 ((INT32) 16069) // FIX(1.961570560)
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#define FIX_2_053119869 ((INT32) 16819) // FIX(2.053119869)
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#define FIX_2_562915447 ((INT32) 20995) // FIX(2.562915447)
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#define FIX_3_072711026 ((INT32) 25172) // FIX(3.072711026)
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#else
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#define FIX_0_298631336 FIX(0.298631336)
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#define FIX_0_390180644 FIX(0.390180644)
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#define FIX_0_541196100 FIX(0.541196100)
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#define FIX_0_765366865 FIX(0.765366865)
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#define FIX_0_899976223 FIX(0.899976223)
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#define FIX_1_175875602 FIX(1.175875602)
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#define FIX_1_501321110 FIX(1.501321110)
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#define FIX_1_847759065 FIX(1.847759065)
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#define FIX_1_961570560 FIX(1.961570560)
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#define FIX_2_053119869 FIX(2.053119869)
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#define FIX_2_562915447 FIX(2.562915447)
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#define FIX_3_072711026 FIX(3.072711026)
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#endif
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// * Multiply an INT32 variable by an INT32 constant to yield an INT32 result. For
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// * 8-bit samples with the recommended scaling, all the variable and constant
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// * values involved are no more than 16 bits wide, so a 16x16->32 bit multiply can
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// * be used instead of a full 32x32 multiply. For 12-bit samples, a full 32-bit
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// * multiplication will be needed.
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#if BITS_IN_JSAMPLE == 8
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#define MULTIPLY(var, const) MULTIPLY16C16(var, const)
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#else
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#define MULTIPLY(var, const) ((var) * (const))
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#endif
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// =======================================================================================================================
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// Dequantize a coefficient by multiplying it by the multiplier-table entry; produce an int result. In this module,
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// both inputs and result are 16 bits or less, so either int or short multiply will work.
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// =======================================================================================================================
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#define DEQUANTIZE(coef, quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval))
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// Perform dequantization and inverse DCT on one block of coefficients.
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#if defined(PSX2_TARGET) && !defined(_DEBUG)
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void fct11(int *pi_tmp0, int *pi_tmp1);
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// special for !!**?!! de code warrior
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void jpeg_idct_islow
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(
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j_decompress_ptr _pst_cinfo,
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jpeg_component_info *_pst_compptr,
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short *_ps_coef_block,
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unsigned char **_ppuc_output_buf,
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unsigned int _ui_output_col
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)
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{
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int i_tmp0, i_tmp1, i_tmp2, i_tmp3;
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int i_tmp10, i_tmp11, i_tmp12, i_tmp13;
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int i_z1, i_z2, i_z3, i_z4, i_z5;
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short *ps_inptr;
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int *pi_quantptr;
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int *pi_wsptr;
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unsigned char *puc_outptr;
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unsigned char *puc_range_limit;
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int i_ctr;
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int ai_workspace[64];
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puc_range_limit = ((_pst_cinfo)->sample_range_limit + 128);
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ps_inptr = _ps_coef_block;
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pi_quantptr = (int *) _pst_compptr->dct_table;
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pi_wsptr = ai_workspace;
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for(i_ctr = 8; i_ctr > 0; i_ctr--)
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{
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if
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(
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(
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ps_inptr[8 * 1] |
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ps_inptr[8 * 2] |
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ps_inptr[8 * 3] |
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ps_inptr[8 * 4] |
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ps_inptr[8 * 5] |
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ps_inptr[8 * 6] |
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ps_inptr[8 * 7]
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) == 0
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)
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{
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int i_dcval;
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i_dcval = (((int) (ps_inptr[8 * 0])) * (pi_quantptr[8 * 0])) << 2;
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pi_wsptr[8 * 0] = i_dcval;
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pi_wsptr[8 * 1] = i_dcval;
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pi_wsptr[8 * 2] = i_dcval;
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pi_wsptr[8 * 3] = i_dcval;
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pi_wsptr[8 * 4] = i_dcval;
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pi_wsptr[8 * 5] = i_dcval;
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pi_wsptr[8 * 6] = i_dcval;
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pi_wsptr[8 * 7] = i_dcval;
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ps_inptr++;
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pi_quantptr++;
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pi_wsptr++;
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}
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else
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{
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i_z2 = (((int) (ps_inptr[8 * 2])) * (pi_quantptr[8 * 2]));
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i_z3 = (((int) (ps_inptr[8 * 6])) * (pi_quantptr[8 * 6]));
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i_z1 = ((i_z2 + i_z3) * (((int) 4433)));
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i_tmp2 = i_z1 + ((i_z3) * (-((int) 15137)));
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i_tmp3 = i_z1 + ((i_z2) * (((int) 6270)));
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fct11(&i_tmp0, &i_tmp1);
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i_z2 = (((int) (ps_inptr[8 * 0])) * (pi_quantptr[8 * 0]));
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i_z3 = (((int) (ps_inptr[8 * 4])) * (pi_quantptr[8 * 4]));
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i_tmp0 = (i_z2 + i_z3) << 13;
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i_tmp1 = (i_z2 - i_z3) << 13;
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i_tmp10 = i_tmp0 + i_tmp3;
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i_tmp13 = i_tmp0 - i_tmp3;
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i_tmp11 = i_tmp1 + i_tmp2;
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i_tmp12 = i_tmp1 - i_tmp2;
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i_tmp0 = (((int) (ps_inptr[8 * 7])) * (pi_quantptr[8 * 7]));
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i_tmp1 = (((int) (ps_inptr[8 * 5])) * (pi_quantptr[8 * 5]));
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i_tmp2 = (((int) (ps_inptr[8 * 3])) * (pi_quantptr[8 * 3]));
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i_tmp3 = (((int) (ps_inptr[8 * 1])) * (pi_quantptr[8 * 1]));
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i_z1 = i_tmp0 + i_tmp3;
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i_z2 = i_tmp1 + i_tmp2;
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i_z3 = i_tmp0 + i_tmp2;
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i_z4 = i_tmp1 + i_tmp3;
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i_z5 = ((i_z3 + i_z4) * (((int) 9633)));
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i_tmp0 = ((i_tmp0) * (((int) 2446)));
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i_tmp1 = ((i_tmp1) * (((int) 16819)));
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i_tmp2 = ((i_tmp2) * (((int) 25172)));
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i_tmp3 = ((i_tmp3) * (((int) 12299)));
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i_z1 = ((i_z1) * (-((int) 7373)));
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i_z2 = ((i_z2) * (-((int) 20995)));
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i_z3 = ((i_z3) * (-((int) 16069)));
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i_z4 = ((i_z4) * (-((int) 3196)));
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i_z3 += i_z5;
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i_z4 += i_z5;
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i_tmp0 += i_z1 + i_z3;
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i_tmp1 += i_z2 + i_z4;
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i_tmp2 += i_z2 + i_z3;
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i_tmp3 += i_z1 + i_z4;
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pi_wsptr[8 * 0] = (int) (((i_tmp10 + i_tmp3) + (((int) 1) << 10)) >> 11);
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pi_wsptr[8 * 7] = (int) (((i_tmp10 - i_tmp3) + (((int) 1) << 10)) >> 11);
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pi_wsptr[8 * 1] = (int) (((i_tmp11 + i_tmp2) + (((int) 1) << 10)) >> 11);
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pi_wsptr[8 * 6] = (int) (((i_tmp11 - i_tmp2) + (((int) 1) << 10)) >> 11);
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pi_wsptr[8 * 2] = (int) (((i_tmp12 + i_tmp1) + (((int) 1) << 10)) >> 11);
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pi_wsptr[8 * 5] = (int) (((i_tmp12 - i_tmp1) + (((int) 1) << 10)) >> 11);
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pi_wsptr[8 * 3] = (int) (((i_tmp13 + i_tmp0) + (((int) 1) << 10)) >> 11);
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pi_wsptr[8 * 4] = (int) (((i_tmp13 - i_tmp0) + (((int) 1) << 10)) >> 11);
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ps_inptr++;
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pi_quantptr++;
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pi_wsptr++;
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}
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}
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pi_wsptr = ai_workspace;
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for(i_ctr = 0; i_ctr < 8; i_ctr++)
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{
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puc_outptr = _ppuc_output_buf[i_ctr] + _ui_output_col;
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if((pi_wsptr[1] | pi_wsptr[2] | pi_wsptr[3] | pi_wsptr[4] | pi_wsptr[5] | pi_wsptr[6] | pi_wsptr[7]) == 0)
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{
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unsigned char uc_dcval;
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uc_dcval = puc_range_limit[(int) ((((int) pi_wsptr[0]) + (((int) 1) << ((2 + 3) - 1))) >> (2 + 3)) & 1023];
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puc_outptr[0] = uc_dcval;
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puc_outptr[1] = uc_dcval;
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puc_outptr[2] = uc_dcval;
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puc_outptr[3] = uc_dcval;
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puc_outptr[4] = uc_dcval;
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puc_outptr[5] = uc_dcval;
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puc_outptr[6] = uc_dcval;
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puc_outptr[7] = uc_dcval;
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pi_wsptr += 8;
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}
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else
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{
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i_z2 = (int) pi_wsptr[2];
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i_z3 = (int) pi_wsptr[6];
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i_z1 = ((i_z2 + i_z3) * (((int) 4433)));
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i_tmp2 = i_z1 + ((i_z3) * (-((int) 15137)));
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i_tmp3 = i_z1 + ((i_z2) * (((int) 6270)));
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fct11(&i_tmp0, &i_tmp1);
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i_tmp0 = ((int) pi_wsptr[0] + (int) pi_wsptr[4]) << 13;
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i_tmp1 = ((int) pi_wsptr[0] - (int) pi_wsptr[4]) << 13;
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i_tmp10 = i_tmp0 + i_tmp3;
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i_tmp13 = i_tmp0 - i_tmp3;
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i_tmp11 = i_tmp1 + i_tmp2;
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i_tmp12 = i_tmp1 - i_tmp2;
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i_tmp0 = (int) pi_wsptr[7];
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i_tmp1 = (int) pi_wsptr[5];
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i_tmp2 = (int) pi_wsptr[3];
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i_tmp3 = (int) pi_wsptr[1];
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i_z1 = i_tmp0 + i_tmp3;
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i_z2 = i_tmp1 + i_tmp2;
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i_z3 = i_tmp0 + i_tmp2;
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i_z4 = i_tmp1 + i_tmp3;
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i_z5 = ((i_z3 + i_z4) * (((int) 9633)));
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i_tmp0 = ((i_tmp0) * (((int) 2446)));
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i_tmp1 = ((i_tmp1) * (((int) 16819)));
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i_tmp2 = ((i_tmp2) * (((int) 25172)));
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i_tmp3 = ((i_tmp3) * (((int) 12299)));
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i_z1 = ((i_z1) * (-((int) 7373)));
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i_z2 = ((i_z2) * (-((int) 20995)));
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i_z3 = ((i_z3) * (-((int) 16069)));
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i_z4 = ((i_z4) * (-((int) 3196)));
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i_z3 += i_z5;
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i_z4 += i_z5;
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i_tmp0 += i_z1 + i_z3;
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i_tmp1 += i_z2 + i_z4;
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i_tmp2 += i_z2 + i_z3;
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i_tmp3 += i_z1 + i_z4;
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puc_outptr[0] = puc_range_limit[(int) (((i_tmp10 + i_tmp3) + (((int) 1) << 17)) >> 18) & 1023];
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puc_outptr[7] = puc_range_limit[(int) (((i_tmp10 - i_tmp3) + (((int) 1) << 17)) >> 18) & 1023];
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puc_outptr[1] = puc_range_limit[(int) (((i_tmp11 + i_tmp2) + (((int) 1) << 17)) >> 18) & 1023];
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puc_outptr[6] = puc_range_limit[(int) (((i_tmp11 - i_tmp2) + (((int) 1) << 17)) >> 18) & 1023];
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puc_outptr[2] = puc_range_limit[(int) (((i_tmp12 + i_tmp1) + (((int) 1) << 17)) >> 18) & 1023];
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puc_outptr[5] = puc_range_limit[(int) (((i_tmp12 - i_tmp1) + (((int) 1) << 17)) >> 18) & 1023];
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puc_outptr[3] = puc_range_limit[(int) (((i_tmp13 + i_tmp0) + (((int) 1) << 17)) >> 18) & 1023];
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puc_outptr[4] = puc_range_limit[(int) (((i_tmp13 - i_tmp0) + (((int) 1) << 17)) >> 18) & 1023];
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pi_wsptr += 8;
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}
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}
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}
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void fct11(int *pi_tmp0, int *pi_tmp1)
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{
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}
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#else
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GLOBAL void jpeg_idct_islow
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(
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j_decompress_ptr cinfo,
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jpeg_component_info *compptr,
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JCOEFPTR coef_block,
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JSAMPARRAY output_buf,
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JDIMENSION output_col
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)
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{
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INT32 tmp0, tmp1, tmp2, tmp3;
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INT32 tmp10, tmp11, tmp12, tmp13;
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INT32 z1, z2, z3, z4, z5;
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JCOEFPTR inptr;
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ISLOW_MULT_TYPE *quantptr;
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int *wsptr;
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JSAMPROW outptr;
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JSAMPLE *range_limit;
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int ctr;
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int workspace[DCTSIZE2]; // buffers data between passes
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SHIFT_TEMPS
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// * Pass 1: process columns from input, store into work array.
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// * Note results are scaled up by sqrt(8) compared to a true IDCT;
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// * furthermore, we scale the results by 2**PASS1_BITS.
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range_limit = IDCT_range_limit(cinfo);
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inptr = coef_block;
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quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
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wsptr = workspace;
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for(ctr = DCTSIZE; ctr > 0; ctr--)
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{
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// * Due to quantization, we will usually find that many of the input coefficients
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// * are zero, especially the AC terms. We can exploit this by short-circuiting the
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// * IDCT calculation for any column in which all the AC terms are zero. In that
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// * case each output is equal to the DC coefficient (with scale factor as needed).
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// * With typical images and quantization tables, half or more of the column DCT
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// * calculations can be simplified this way.
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if
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(
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(
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inptr[DCTSIZE * 1] |
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inptr[DCTSIZE * 2] |
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inptr[DCTSIZE * 3] |
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inptr[DCTSIZE * 4] |
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inptr[DCTSIZE * 5] |
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inptr[DCTSIZE * 6] |
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inptr[DCTSIZE * 7]
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) == 0
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)
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{
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// AC terms all zero
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int dcval;
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dcval = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]) << PASS1_BITS;
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wsptr[DCTSIZE * 0] = dcval;
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wsptr[DCTSIZE * 1] = dcval;
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wsptr[DCTSIZE * 2] = dcval;
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wsptr[DCTSIZE * 3] = dcval;
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wsptr[DCTSIZE * 4] = dcval;
|
|
wsptr[DCTSIZE * 5] = dcval;
|
|
wsptr[DCTSIZE * 6] = dcval;
|
|
wsptr[DCTSIZE * 7] = dcval;
|
|
|
|
inptr++; // advance pointers to next column
|
|
quantptr++;
|
|
wsptr++;
|
|
continue;
|
|
}
|
|
|
|
// * Even part: reverse the even part of the forward DCT.
|
|
// * The rotator is sqrt(2)*c(-6).
|
|
z2 = DEQUANTIZE(inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2]);
|
|
z3 = DEQUANTIZE(inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6]);
|
|
|
|
z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
|
|
tmp2 = z1 + MULTIPLY(z3, -FIX_1_847759065);
|
|
tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
|
|
|
|
z2 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
|
|
z3 = DEQUANTIZE(inptr[DCTSIZE * 4], quantptr[DCTSIZE * 4]);
|
|
|
|
tmp0 = (z2 + z3) << CONST_BITS;
|
|
tmp1 = (z2 - z3) << CONST_BITS;
|
|
|
|
tmp10 = tmp0 + tmp3;
|
|
tmp13 = tmp0 - tmp3;
|
|
tmp11 = tmp1 + tmp2;
|
|
tmp12 = tmp1 - tmp2;
|
|
|
|
// * Odd part per figure 8; the matrix is unitary and hence its transpose is its
|
|
// * inverse. i0..i3 are y7,y5,y3,y1 respectively.
|
|
tmp0 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
|
|
tmp1 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
|
|
tmp2 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
|
|
tmp3 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);
|
|
|
|
z1 = tmp0 + tmp3;
|
|
z2 = tmp1 + tmp2;
|
|
z3 = tmp0 + tmp2;
|
|
z4 = tmp1 + tmp3;
|
|
z5 = MULTIPLY(z3 + z4, FIX_1_175875602); // sqrt(2) * c3
|
|
|
|
tmp0 = MULTIPLY(tmp0, FIX_0_298631336); // sqrt(2) * (-c1+c3+c5-c7)
|
|
tmp1 = MULTIPLY(tmp1, FIX_2_053119869); // sqrt(2) * ( c1+c3-c5+c7)
|
|
tmp2 = MULTIPLY(tmp2, FIX_3_072711026); // sqrt(2) * ( c1+c3+c5-c7)
|
|
tmp3 = MULTIPLY(tmp3, FIX_1_501321110); // sqrt(2) * ( c1+c3-c5-c7)
|
|
z1 = MULTIPLY(z1, -FIX_0_899976223); // sqrt(2) * (c7-c3)
|
|
z2 = MULTIPLY(z2, -FIX_2_562915447); // sqrt(2) * (-c1-c3)
|
|
z3 = MULTIPLY(z3, -FIX_1_961570560); // sqrt(2) * (-c3-c5)
|
|
z4 = MULTIPLY(z4, -FIX_0_390180644); // sqrt(2) * (c5-c3)
|
|
|
|
z3 += z5;
|
|
z4 += z5;
|
|
|
|
tmp0 += z1 + z3;
|
|
tmp1 += z2 + z4;
|
|
tmp2 += z2 + z3;
|
|
tmp3 += z1 + z4;
|
|
|
|
// Final output stage: inputs are tmp10..tmp13, tmp0..tmp3
|
|
wsptr[DCTSIZE * 0] = (int) DESCALE(tmp10 + tmp3, CONST_BITS - PASS1_BITS);
|
|
wsptr[DCTSIZE * 7] = (int) DESCALE(tmp10 - tmp3, CONST_BITS - PASS1_BITS);
|
|
wsptr[DCTSIZE * 1] = (int) DESCALE(tmp11 + tmp2, CONST_BITS - PASS1_BITS);
|
|
wsptr[DCTSIZE * 6] = (int) DESCALE(tmp11 - tmp2, CONST_BITS - PASS1_BITS);
|
|
wsptr[DCTSIZE * 2] = (int) DESCALE(tmp12 + tmp1, CONST_BITS - PASS1_BITS);
|
|
wsptr[DCTSIZE * 5] = (int) DESCALE(tmp12 - tmp1, CONST_BITS - PASS1_BITS);
|
|
wsptr[DCTSIZE * 3] = (int) DESCALE(tmp13 + tmp0, CONST_BITS - PASS1_BITS);
|
|
wsptr[DCTSIZE * 4] = (int) DESCALE(tmp13 - tmp0, CONST_BITS - PASS1_BITS);
|
|
|
|
inptr++; // advance pointers to next column
|
|
quantptr++;
|
|
wsptr++;
|
|
}
|
|
|
|
// * Pass 2: process rows from work array, store into output array.
|
|
// * Note that we must descale the results by a factor of 8 == 2**3,
|
|
// * and also undo the PASS1_BITS scaling.
|
|
wsptr = workspace;
|
|
for(ctr = 0; ctr < DCTSIZE; ctr++)
|
|
{
|
|
outptr = output_buf[ctr] + output_col;
|
|
|
|
// * Rows of zeroes can be exploited in the same way as we did with columns.
|
|
// * However, the column calculation has created many nonzero AC terms, so the
|
|
// * simplification applies less often (typically 5% to 10% of the time). On
|
|
// * machines with very fast multiplication, it's possible that the test takes more
|
|
// * time than it's worth. In that case this section may be commented out.
|
|
#ifndef NO_ZERO_ROW_TEST
|
|
if((wsptr[1] | wsptr[2] | wsptr[3] | wsptr[4] | wsptr[5] | wsptr[6] | wsptr[7]) == 0)
|
|
{
|
|
|
|
// AC terms all zero
|
|
JSAMPLE dcval;
|
|
|
|
dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS + 3) & RANGE_MASK];
|
|
|
|
outptr[0] = dcval;
|
|
outptr[1] = dcval;
|
|
outptr[2] = dcval;
|
|
outptr[3] = dcval;
|
|
outptr[4] = dcval;
|
|
outptr[5] = dcval;
|
|
outptr[6] = dcval;
|
|
outptr[7] = dcval;
|
|
|
|
wsptr += DCTSIZE; // advance pointer to next row
|
|
continue;
|
|
}
|
|
|
|
#endif
|
|
// * Even part: reverse the even part of the forward DCT.
|
|
// * The rotator is sqrt(2)*c(-6).
|
|
z2 = (INT32) wsptr[2];
|
|
z3 = (INT32) wsptr[6];
|
|
|
|
z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
|
|
tmp2 = z1 + MULTIPLY(z3, -FIX_1_847759065);
|
|
tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
|
|
|
|
tmp0 = ((INT32) wsptr[0] + (INT32) wsptr[4]) << CONST_BITS;
|
|
tmp1 = ((INT32) wsptr[0] - (INT32) wsptr[4]) << CONST_BITS;
|
|
|
|
tmp10 = tmp0 + tmp3;
|
|
tmp13 = tmp0 - tmp3;
|
|
tmp11 = tmp1 + tmp2;
|
|
tmp12 = tmp1 - tmp2;
|
|
|
|
// * Odd part per figure 8; the matrix is unitary and hence its transpose is its
|
|
// * inverse. i0..i3 are y7,y5,y3,y1 respectively.
|
|
tmp0 = (INT32) wsptr[7];
|
|
tmp1 = (INT32) wsptr[5];
|
|
tmp2 = (INT32) wsptr[3];
|
|
tmp3 = (INT32) wsptr[1];
|
|
|
|
z1 = tmp0 + tmp3;
|
|
z2 = tmp1 + tmp2;
|
|
z3 = tmp0 + tmp2;
|
|
z4 = tmp1 + tmp3;
|
|
z5 = MULTIPLY(z3 + z4, FIX_1_175875602); // sqrt(2) * c3
|
|
|
|
tmp0 = MULTIPLY(tmp0, FIX_0_298631336); // sqrt(2) * (-c1+c3+c5-c7)
|
|
tmp1 = MULTIPLY(tmp1, FIX_2_053119869); // sqrt(2) * ( c1+c3-c5+c7)
|
|
tmp2 = MULTIPLY(tmp2, FIX_3_072711026); // sqrt(2) * ( c1+c3+c5-c7)
|
|
tmp3 = MULTIPLY(tmp3, FIX_1_501321110); // sqrt(2) * ( c1+c3-c5-c7)
|
|
z1 = MULTIPLY(z1, -FIX_0_899976223); // sqrt(2) * (c7-c3)
|
|
z2 = MULTIPLY(z2, -FIX_2_562915447); // sqrt(2) * (-c1-c3)
|
|
z3 = MULTIPLY(z3, -FIX_1_961570560); // sqrt(2) * (-c3-c5)
|
|
z4 = MULTIPLY(z4, -FIX_0_390180644); // sqrt(2) * (c5-c3)
|
|
|
|
z3 += z5;
|
|
z4 += z5;
|
|
|
|
tmp0 += z1 + z3;
|
|
tmp1 += z2 + z4;
|
|
tmp2 += z2 + z3;
|
|
tmp3 += z1 + z4;
|
|
|
|
// Final output stage: inputs are tmp10..tmp13, tmp0..tmp3
|
|
outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp3, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
outptr[7] = range_limit[(int) DESCALE(tmp10 - tmp3, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
outptr[1] = range_limit[(int) DESCALE(tmp11 + tmp2, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
outptr[6] = range_limit[(int) DESCALE(tmp11 - tmp2, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
outptr[2] = range_limit[(int) DESCALE(tmp12 + tmp1, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
outptr[5] = range_limit[(int) DESCALE(tmp12 - tmp1, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
outptr[3] = range_limit[(int) DESCALE(tmp13 + tmp0, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
outptr[4] = range_limit[(int) DESCALE(tmp13 - tmp0, CONST_BITS + PASS1_BITS + 3) & RANGE_MASK];
|
|
|
|
wsptr += DCTSIZE; // advance pointer to next row
|
|
}
|
|
}
|
|
|
|
#endif
|
|
#endif // DCT_ISLOW_SUPPORTED
|