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Diffstat (limited to '')
| -rw-r--r-- | libjpegtwrp/jfdctfst.c | 224 |
1 files changed, 0 insertions, 224 deletions
diff --git a/libjpegtwrp/jfdctfst.c b/libjpegtwrp/jfdctfst.c deleted file mode 100644 index ccb378a3b..000000000 --- a/libjpegtwrp/jfdctfst.c +++ /dev/null @@ -1,224 +0,0 @@ -/* - * jfdctfst.c - * - * Copyright (C) 1994-1996, Thomas G. Lane. - * This file is part of the Independent JPEG Group's software. - * For conditions of distribution and use, see the accompanying README file. - * - * This file contains a fast, not so accurate integer implementation of the - * forward DCT (Discrete Cosine Transform). - * - * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT - * on each column. Direct algorithms are also available, but they are - * much more complex and seem not to be any faster when reduced to code. - * - * This implementation is based on Arai, Agui, and Nakajima's algorithm for - * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in - * Japanese, but the algorithm is described in the Pennebaker & Mitchell - * JPEG textbook (see REFERENCES section in file README). The following code - * is based directly on figure 4-8 in P&M. - * While an 8-point DCT cannot be done in less than 11 multiplies, it is - * possible to arrange the computation so that many of the multiplies are - * simple scalings of the final outputs. These multiplies can then be - * folded into the multiplications or divisions by the JPEG quantization - * table entries. The AA&N method leaves only 5 multiplies and 29 adds - * to be done in the DCT itself. - * The primary disadvantage of this method is that with fixed-point math, - * accuracy is lost due to imprecise representation of the scaled - * quantization values. The smaller the quantization table entry, the less - * precise the scaled value, so this implementation does worse with high- - * quality-setting files than with low-quality ones. - */ - -#define JPEG_INTERNALS -#include "jinclude.h" -#include "jpeglib.h" -#include "jdct.h" /* Private declarations for DCT subsystem */ - -#ifdef DCT_IFAST_SUPPORTED - - -/* - * This module is specialized to the case DCTSIZE = 8. - */ - -#if DCTSIZE != 8 - Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ -#endif - - -/* Scaling decisions are generally the same as in the LL&M algorithm; - * see jfdctint.c for more details. However, we choose to descale - * (right shift) multiplication products as soon as they are formed, - * rather than carrying additional fractional bits into subsequent additions. - * This compromises accuracy slightly, but it lets us save a few shifts. - * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples) - * everywhere except in the multiplications proper; this saves a good deal - * of work on 16-bit-int machines. - * - * Again to save a few shifts, the intermediate results between pass 1 and - * pass 2 are not upscaled, but are represented only to integral precision. - * - * A final compromise is to represent the multiplicative constants to only - * 8 fractional bits, rather than 13. This saves some shifting work on some - * machines, and may also reduce the cost of multiplication (since there - * are fewer one-bits in the constants). - */ - -#define CONST_BITS 8 - - -/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus - * causing a lot of useless floating-point operations at run time. - * To get around this we use the following pre-calculated constants. - * If you change CONST_BITS you may want to add appropriate values. - * (With a reasonable C compiler, you can just rely on the FIX() macro...) - */ - -#if CONST_BITS == 8 -#define FIX_0_382683433 ((INT32) 98) /* FIX(0.382683433) */ -#define FIX_0_541196100 ((INT32) 139) /* FIX(0.541196100) */ -#define FIX_0_707106781 ((INT32) 181) /* FIX(0.707106781) */ -#define FIX_1_306562965 ((INT32) 334) /* FIX(1.306562965) */ -#else -#define FIX_0_382683433 FIX(0.382683433) -#define FIX_0_541196100 FIX(0.541196100) -#define FIX_0_707106781 FIX(0.707106781) -#define FIX_1_306562965 FIX(1.306562965) -#endif - - -/* We can gain a little more speed, with a further compromise in accuracy, - * by omitting the addition in a descaling shift. This yields an incorrectly - * rounded result half the time... - */ - -#ifndef USE_ACCURATE_ROUNDING -#undef DESCALE -#define DESCALE(x,n) RIGHT_SHIFT(x, n) -#endif - - -/* Multiply a DCTELEM variable by an INT32 constant, and immediately - * descale to yield a DCTELEM result. - */ - -#define MULTIPLY(var,const) ((DCTELEM) DESCALE((var) * (const), CONST_BITS)) - - -/* - * Perform the forward DCT on one block of samples. - */ - -GLOBAL(void) -jpeg_fdct_ifast (DCTELEM * data) -{ - DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; - DCTELEM tmp10, tmp11, tmp12, tmp13; - DCTELEM z1, z2, z3, z4, z5, z11, z13; - DCTELEM *dataptr; - int ctr; - SHIFT_TEMPS - - /* Pass 1: process rows. */ - - dataptr = data; - for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { - tmp0 = dataptr[0] + dataptr[7]; - tmp7 = dataptr[0] - dataptr[7]; - tmp1 = dataptr[1] + dataptr[6]; - tmp6 = dataptr[1] - dataptr[6]; - tmp2 = dataptr[2] + dataptr[5]; - tmp5 = dataptr[2] - dataptr[5]; - tmp3 = dataptr[3] + dataptr[4]; - tmp4 = dataptr[3] - dataptr[4]; - - /* Even part */ - - tmp10 = tmp0 + tmp3; /* phase 2 */ - tmp13 = tmp0 - tmp3; - tmp11 = tmp1 + tmp2; - tmp12 = tmp1 - tmp2; - - dataptr[0] = tmp10 + tmp11; /* phase 3 */ - dataptr[4] = tmp10 - tmp11; - - z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ - dataptr[2] = tmp13 + z1; /* phase 5 */ - dataptr[6] = tmp13 - z1; - - /* Odd part */ - - tmp10 = tmp4 + tmp5; /* phase 2 */ - tmp11 = tmp5 + tmp6; - tmp12 = tmp6 + tmp7; - - /* The rotator is modified from fig 4-8 to avoid extra negations. */ - z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ - z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ - z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ - z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ - - z11 = tmp7 + z3; /* phase 5 */ - z13 = tmp7 - z3; - - dataptr[5] = z13 + z2; /* phase 6 */ - dataptr[3] = z13 - z2; - dataptr[1] = z11 + z4; - dataptr[7] = z11 - z4; - - dataptr += DCTSIZE; /* advance pointer to next row */ - } - - /* Pass 2: process columns. */ - - dataptr = data; - for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { - tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7]; - tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7]; - tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6]; - tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6]; - tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5]; - tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5]; - tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4]; - tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4]; - - /* Even part */ - - tmp10 = tmp0 + tmp3; /* phase 2 */ - tmp13 = tmp0 - tmp3; - tmp11 = tmp1 + tmp2; - tmp12 = tmp1 - tmp2; - - dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */ - dataptr[DCTSIZE*4] = tmp10 - tmp11; - - z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ - dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */ - dataptr[DCTSIZE*6] = tmp13 - z1; - - /* Odd part */ - - tmp10 = tmp4 + tmp5; /* phase 2 */ - tmp11 = tmp5 + tmp6; - tmp12 = tmp6 + tmp7; - - /* The rotator is modified from fig 4-8 to avoid extra negations. */ - z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ - z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ - z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ - z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ - - z11 = tmp7 + z3; /* phase 5 */ - z13 = tmp7 - z3; - - dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */ - dataptr[DCTSIZE*3] = z13 - z2; - dataptr[DCTSIZE*1] = z11 + z4; - dataptr[DCTSIZE*7] = z11 - z4; - - dataptr++; /* advance pointer to next column */ - } -} - -#endif /* DCT_IFAST_SUPPORTED */ |