| 1 | /********************************************************************** <BR>
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| 2 | This file is part of Crack dot Com's free source code release of
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| 3 | Golgotha. <a href="http://www.crack.com/golgotha_release"> <BR> for
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| 4 | information about compiling & licensing issues visit this URL</a>
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| 5 | <PRE> If that doesn't help, contact Jonathan Clark at
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| 6 | golgotha_source@usa.net (Subject should have "GOLG" in it)
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| 7 | ***********************************************************************/
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| 8 |
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| 9 | /*
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| 10 | * jidctint.c
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| 11 | *
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| 12 | * Copyright (C) 1991-1996, Thomas G. Lane.
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| 13 | * This file is part of the Independent JPEG Group's software.
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| 14 | * For conditions of distribution and use, see the accompanying README file.
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| 15 | *
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| 16 | * This file contains a slow-but-accurate integer implementation of the
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| 17 | * inverse DCT (Discrete Cosine Transform). In the IJG code, this routine
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| 18 | * must also perform dequantization of the input coefficients.
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| 19 | *
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| 20 | * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
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| 21 | * on each row (or vice versa, but it's more convenient to emit a row at
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| 22 | * a time). Direct algorithms are also available, but they are much more
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| 23 | * complex and seem not to be any faster when reduced to code.
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| 24 | *
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| 25 | * This implementation is based on an algorithm described in
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| 26 | * C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT
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| 27 | * Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics,
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| 28 | * Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991.
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| 29 | * The primary algorithm described there uses 11 multiplies and 29 adds.
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| 30 | * We use their alternate method with 12 multiplies and 32 adds.
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| 31 | * The advantage of this method is that no data path contains more than one
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| 32 | * multiplication; this allows a very simple and accurate implementation in
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| 33 | * scaled fixed-point arithmetic, with a minimal number of shifts.
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| 34 | */
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| 35 |
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| 36 | #define JPEG_INTERNALS
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| 37 | #include "loaders/jpg/jinclude.h"
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| 38 | #include "loaders/jpg/jpeglib.h"
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| 39 | #include "loaders/jpg/jdct.h" /* Private declarations for DCT subsystem */
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| 40 |
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| 41 | #ifdef DCT_ISLOW_SUPPORTED
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| 42 |
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| 43 |
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| 44 | /*
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| 45 | * This module is specialized to the case DCTSIZE = 8.
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| 46 | */
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| 47 |
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| 48 | #if DCTSIZE != 8
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| 49 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
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| 50 | #endif
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| 51 |
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| 52 |
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| 53 | /*
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| 54 | * The poop on this scaling stuff is as follows:
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| 55 | *
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| 56 | * Each 1-D IDCT step produces outputs which are a factor of sqrt(N)
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| 57 | * larger than the true IDCT outputs. The final outputs are therefore
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| 58 | * a factor of N larger than desired; since N=8 this can be cured by
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| 59 | * a simple right shift at the end of the algorithm. The advantage of
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| 60 | * this arrangement is that we save two multiplications per 1-D IDCT,
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| 61 | * because the y0 and y4 inputs need not be divided by sqrt(N).
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| 62 | *
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| 63 | * We have to do addition and subtraction of the integer inputs, which
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| 64 | * is no problem, and multiplication by fractional constants, which is
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| 65 | * a problem to do in integer arithmetic. We multiply all the constants
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| 66 | * by CONST_SCALE and convert them to integer constants (thus retaining
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| 67 | * CONST_BITS bits of precision in the constants). After doing a
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| 68 | * multiplication we have to divide the product by CONST_SCALE, with proper
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| 69 | * rounding, to produce the correct output. This division can be done
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| 70 | * cheaply as a right shift of CONST_BITS bits. We postpone shifting
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| 71 | * as long as possible so that partial sums can be added together with
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| 72 | * full fractional precision.
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| 73 | *
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| 74 | * The outputs of the first pass are scaled up by PASS1_BITS bits so that
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| 75 | * they are represented to better-than-integral precision. These outputs
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| 76 | * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word
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| 77 | * with the recommended scaling. (To scale up 12-bit sample data further, an
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| 78 | * intermediate INT32 array would be needed.)
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| 79 | *
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| 80 | * To avoid overflow of the 32-bit intermediate results in pass 2, we must
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| 81 | * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26. Error analysis
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| 82 | * shows that the values given below are the most effective.
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| 83 | */
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| 84 |
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| 85 | #if BITS_IN_JSAMPLE == 8
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| 86 | #define CONST_BITS 13
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| 87 | #define PASS1_BITS 2
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| 88 | #else
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| 89 | #define CONST_BITS 13
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| 90 | #define PASS1_BITS 1 /* lose a little precision to avoid overflow */
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| 91 | #endif
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| 92 |
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| 93 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
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| 94 | * causing a lot of useless floating-point operations at run time.
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| 95 | * To get around this we use the following pre-calculated constants.
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| 96 | * If you change CONST_BITS you may want to add appropriate values.
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| 97 | * (With a reasonable C compiler, you can just rely on the FIX() macro...)
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| 98 | */
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| 99 |
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| 100 | #if CONST_BITS == 13
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| 101 | #define FIX_0_298631336 ((INT32) 2446) /* FIX(0.298631336) */
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| 102 | #define FIX_0_390180644 ((INT32) 3196) /* FIX(0.390180644) */
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| 103 | #define FIX_0_541196100 ((INT32) 4433) /* FIX(0.541196100) */
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| 104 | #define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */
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| 105 | #define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */
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| 106 | #define FIX_1_175875602 ((INT32) 9633) /* FIX(1.175875602) */
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| 107 | #define FIX_1_501321110 ((INT32) 12299) /* FIX(1.501321110) */
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| 108 | #define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */
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| 109 | #define FIX_1_961570560 ((INT32) 16069) /* FIX(1.961570560) */
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| 110 | #define FIX_2_053119869 ((INT32) 16819) /* FIX(2.053119869) */
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| 111 | #define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */
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| 112 | #define FIX_3_072711026 ((INT32) 25172) /* FIX(3.072711026) */
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| 113 | #else
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| 114 | #define FIX_0_298631336 FIX(0.298631336)
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| 115 | #define FIX_0_390180644 FIX(0.390180644)
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| 116 | #define FIX_0_541196100 FIX(0.541196100)
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| 117 | #define FIX_0_765366865 FIX(0.765366865)
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| 118 | #define FIX_0_899976223 FIX(0.899976223)
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| 119 | #define FIX_1_175875602 FIX(1.175875602)
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| 120 | #define FIX_1_501321110 FIX(1.501321110)
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| 121 | #define FIX_1_847759065 FIX(1.847759065)
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| 122 | #define FIX_1_961570560 FIX(1.961570560)
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| 123 | #define FIX_2_053119869 FIX(2.053119869)
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| 124 | #define FIX_2_562915447 FIX(2.562915447)
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| 125 | #define FIX_3_072711026 FIX(3.072711026)
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| 126 | #endif
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| 127 |
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| 128 |
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| 129 | /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
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| 130 | * For 8-bit samples with the recommended scaling, all the variable
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| 131 | * and constant values involved are no more than 16 bits wide, so a
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| 132 | * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
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| 133 | * For 12-bit samples, a full 32-bit multiplication will be needed.
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| 134 | */
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| 135 |
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| 136 | #if BITS_IN_JSAMPLE == 8
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| 137 | #define MULTIPLY(var,const) MULTIPLY16C16(var,const)
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| 138 | #else
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| 139 | #define MULTIPLY(var,const) ((var) * (const))
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| 140 | #endif
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| 141 |
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| 142 |
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| 143 | /* Dequantize a coefficient by multiplying it by the multiplier-table
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| 144 | * entry; produce an int result. In this module, both inputs and result
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| 145 | * are 16 bits or less, so either int or short multiply will work.
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| 146 | */
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| 147 |
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| 148 | #define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval))
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| 149 |
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| 150 |
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| 151 | /*
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| 152 | * Perform dequantization and inverse DCT on one block of coefficients.
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| 153 | */
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| 154 |
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| 155 | GLOBAL(void)
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| 156 | jpeg_idct_islow (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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| 157 | JCOEFPTR coef_block,
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| 158 | JSAMPARRAY output_buf, JDIMENSION output_col)
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| 159 | {
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| 160 | INT32 tmp0, tmp1, tmp2, tmp3;
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| 161 | INT32 tmp10, tmp11, tmp12, tmp13;
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| 162 | INT32 z1, z2, z3, z4, z5;
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| 163 | JCOEFPTR inptr;
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| 164 | ISLOW_MULT_TYPE * quantptr;
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| 165 | int * wsptr;
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| 166 | JSAMPROW outptr;
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| 167 | JSAMPLE *range_limit = IDCT_range_limit(cinfo);
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| 168 | int ctr;
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| 169 | int workspace[DCTSIZE2]; /* buffers data between passes */
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| 170 | SHIFT_TEMPS
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| 171 |
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| 172 | /* Pass 1: process columns from input, store into work array. */
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| 173 | /* Note results are scaled up by sqrt(8) compared to a true IDCT; */
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| 174 | /* furthermore, we scale the results by 2**PASS1_BITS. */
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| 175 |
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| 176 | inptr = coef_block;
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| 177 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
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| 178 | wsptr = workspace;
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| 179 | for (ctr = DCTSIZE; ctr > 0; ctr--) {
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| 180 | /* Due to quantization, we will usually find that many of the input
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| 181 | * coefficients are zero, especially the AC terms. We can exploit this
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| 182 | * by short-circuiting the IDCT calculation for any column in which all
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| 183 | * the AC terms are zero. In that case each output is equal to the
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| 184 | * DC coefficient (with scale factor as needed).
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| 185 | * With typical images and quantization tables, half or more of the
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| 186 | * column DCT calculations can be simplified this way.
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| 187 | */
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| 188 |
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| 189 | if ((inptr[DCTSIZE*1] | inptr[DCTSIZE*2] | inptr[DCTSIZE*3] |
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| 190 | inptr[DCTSIZE*4] | inptr[DCTSIZE*5] | inptr[DCTSIZE*6] |
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| 191 | inptr[DCTSIZE*7]) == 0) {
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| 192 | /* AC terms all zero */
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| 193 | int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
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| 194 |
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| 195 | wsptr[DCTSIZE*0] = dcval;
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| 196 | wsptr[DCTSIZE*1] = dcval;
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| 197 | wsptr[DCTSIZE*2] = dcval;
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| 198 | wsptr[DCTSIZE*3] = dcval;
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| 199 | wsptr[DCTSIZE*4] = dcval;
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| 200 | wsptr[DCTSIZE*5] = dcval;
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| 201 | wsptr[DCTSIZE*6] = dcval;
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| 202 | wsptr[DCTSIZE*7] = dcval;
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| 203 |
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| 204 | inptr++; /* advance pointers to next column */
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| 205 | quantptr++;
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| 206 | wsptr++;
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| 207 | continue;
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| 208 | }
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| 209 |
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| 210 | /* Even part: reverse the even part of the forward DCT. */
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| 211 | /* The rotator is sqrt(2)*c(-6). */
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| 212 |
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| 213 | z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
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| 214 | z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
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| 215 |
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| 216 | z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
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| 217 | tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
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| 218 | tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
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| 219 |
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| 220 | z2 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
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| 221 | z3 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
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| 222 |
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| 223 | tmp0 = (z2 + z3) << CONST_BITS;
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| 224 | tmp1 = (z2 - z3) << CONST_BITS;
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| 225 |
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| 226 | tmp10 = tmp0 + tmp3;
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| 227 | tmp13 = tmp0 - tmp3;
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| 228 | tmp11 = tmp1 + tmp2;
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| 229 | tmp12 = tmp1 - tmp2;
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| 230 |
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| 231 | /* Odd part per figure 8; the matrix is unitary and hence its
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| 232 | * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
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| 233 | */
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| 234 |
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| 235 | tmp0 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
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| 236 | tmp1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
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| 237 | tmp2 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
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| 238 | tmp3 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
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| 239 |
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| 240 | z1 = tmp0 + tmp3;
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| 241 | z2 = tmp1 + tmp2;
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| 242 | z3 = tmp0 + tmp2;
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| 243 | z4 = tmp1 + tmp3;
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| 244 | z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
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| 245 |
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| 246 | tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
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| 247 | tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
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| 248 | tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
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| 249 | tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
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| 250 | z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
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| 251 | z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
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| 252 | z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
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| 253 | z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
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| 254 |
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| 255 | z3 += z5;
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| 256 | z4 += z5;
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| 257 |
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| 258 | tmp0 += z1 + z3;
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| 259 | tmp1 += z2 + z4;
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| 260 | tmp2 += z2 + z3;
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| 261 | tmp3 += z1 + z4;
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| 262 |
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| 263 | /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
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| 264 |
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| 265 | wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS);
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| 266 | wsptr[DCTSIZE*7] = (int) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS);
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| 267 | wsptr[DCTSIZE*1] = (int) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS);
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| 268 | wsptr[DCTSIZE*6] = (int) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS);
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| 269 | wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS);
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| 270 | wsptr[DCTSIZE*5] = (int) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS);
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| 271 | wsptr[DCTSIZE*3] = (int) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS);
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| 272 | wsptr[DCTSIZE*4] = (int) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS);
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| 273 |
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| 274 | inptr++; /* advance pointers to next column */
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| 275 | quantptr++;
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| 276 | wsptr++;
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| 277 | }
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| 278 |
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| 279 | /* Pass 2: process rows from work array, store into output array. */
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| 280 | /* Note that we must descale the results by a factor of 8 == 2**3, */
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| 281 | /* and also undo the PASS1_BITS scaling. */
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| 282 |
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| 283 | wsptr = workspace;
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| 284 | for (ctr = 0; ctr < DCTSIZE; ctr++) {
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| 285 | outptr = output_buf[ctr] + output_col;
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| 286 | /* Rows of zeroes can be exploited in the same way as we did with columns.
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| 287 | * However, the column calculation has created many nonzero AC terms, so
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| 288 | * the simplification applies less often (typically 5% to 10% of the time).
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| 289 | * On machines with very fast multiplication, it's possible that the
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| 290 | * test takes more time than it's worth. In that case this section
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| 291 | * may be commented out.
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| 292 | */
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| 293 |
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| 294 | #ifndef NO_ZERO_ROW_TEST
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| 295 | if ((wsptr[1] | wsptr[2] | wsptr[3] | wsptr[4] | wsptr[5] | wsptr[6] |
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| 296 | wsptr[7]) == 0) {
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| 297 | /* AC terms all zero */
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| 298 | JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
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| 299 | & RANGE_MASK];
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| 300 |
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| 301 | outptr[0] = dcval;
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| 302 | outptr[1] = dcval;
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| 303 | outptr[2] = dcval;
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| 304 | outptr[3] = dcval;
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| 305 | outptr[4] = dcval;
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| 306 | outptr[5] = dcval;
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| 307 | outptr[6] = dcval;
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| 308 | outptr[7] = dcval;
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| 309 |
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| 310 | wsptr += DCTSIZE; /* advance pointer to next row */
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| 311 | continue;
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| 312 | }
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| 313 | #endif
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| 314 |
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| 315 | /* Even part: reverse the even part of the forward DCT. */
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| 316 | /* The rotator is sqrt(2)*c(-6). */
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| 317 |
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| 318 | z2 = (INT32) wsptr[2];
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| 319 | z3 = (INT32) wsptr[6];
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| 320 |
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| 321 | z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
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| 322 | tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
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| 323 | tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
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| 324 |
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| 325 | tmp0 = ((INT32) wsptr[0] + (INT32) wsptr[4]) << CONST_BITS;
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| 326 | tmp1 = ((INT32) wsptr[0] - (INT32) wsptr[4]) << CONST_BITS;
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| 327 |
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| 328 | tmp10 = tmp0 + tmp3;
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| 329 | tmp13 = tmp0 - tmp3;
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| 330 | tmp11 = tmp1 + tmp2;
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| 331 | tmp12 = tmp1 - tmp2;
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| 332 |
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| 333 | /* Odd part per figure 8; the matrix is unitary and hence its
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| 334 | * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
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| 335 | */
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| 336 |
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| 337 | tmp0 = (INT32) wsptr[7];
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| 338 | tmp1 = (INT32) wsptr[5];
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| 339 | tmp2 = (INT32) wsptr[3];
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| 340 | tmp3 = (INT32) wsptr[1];
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| 341 |
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| 342 | z1 = tmp0 + tmp3;
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| 343 | z2 = tmp1 + tmp2;
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| 344 | z3 = tmp0 + tmp2;
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| 345 | z4 = tmp1 + tmp3;
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| 346 | z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
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| 347 |
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| 348 | tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
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| 349 | tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
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| 350 | tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
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| 351 | tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
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| 352 | z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
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| 353 | z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
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| 354 | z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
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| 355 | z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
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| 356 |
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| 357 | z3 += z5;
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| 358 | z4 += z5;
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| 359 |
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| 360 | tmp0 += z1 + z3;
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| 361 | tmp1 += z2 + z4;
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| 362 | tmp2 += z2 + z3;
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| 363 | tmp3 += z1 + z4;
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| 364 |
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| 365 | /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
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| 366 |
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| 367 | outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp3,
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| 368 | CONST_BITS+PASS1_BITS+3)
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| 369 | & RANGE_MASK];
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| 370 | outptr[7] = range_limit[(int) DESCALE(tmp10 - tmp3,
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| 371 | CONST_BITS+PASS1_BITS+3)
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| 372 | & RANGE_MASK];
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| 373 | outptr[1] = range_limit[(int) DESCALE(tmp11 + tmp2,
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| 374 | CONST_BITS+PASS1_BITS+3)
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| 375 | & RANGE_MASK];
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| 376 | outptr[6] = range_limit[(int) DESCALE(tmp11 - tmp2,
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| 377 | CONST_BITS+PASS1_BITS+3)
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| 378 | & RANGE_MASK];
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| 379 | outptr[2] = range_limit[(int) DESCALE(tmp12 + tmp1,
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| 380 | CONST_BITS+PASS1_BITS+3)
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| 381 | & RANGE_MASK];
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| 382 | outptr[5] = range_limit[(int) DESCALE(tmp12 - tmp1,
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| 383 | CONST_BITS+PASS1_BITS+3)
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| 384 | & RANGE_MASK];
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| 385 | outptr[3] = range_limit[(int) DESCALE(tmp13 + tmp0,
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| 386 | CONST_BITS+PASS1_BITS+3)
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| 387 | & RANGE_MASK];
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| 388 | outptr[4] = range_limit[(int) DESCALE(tmp13 - tmp0,
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| 389 | CONST_BITS+PASS1_BITS+3)
|
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| 390 | & RANGE_MASK];
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| 391 |
|
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| 392 | wsptr += DCTSIZE; /* advance pointer to next row */
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| 393 | }
|
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| 394 | }
|
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| 395 |
|
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| 396 | #endif /* DCT_ISLOW_SUPPORTED */
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