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Diffstat (limited to 'libjpegtwrp/jidctfst.c')
| -rw-r--r-- | libjpegtwrp/jidctfst.c | 368 |
1 files changed, 0 insertions, 368 deletions
diff --git a/libjpegtwrp/jidctfst.c b/libjpegtwrp/jidctfst.c deleted file mode 100644 index dba4216fb..000000000 --- a/libjpegtwrp/jidctfst.c +++ /dev/null @@ -1,368 +0,0 @@ -/* - * jidctfst.c - * - * Copyright (C) 1994-1998, 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 - * inverse DCT (Discrete Cosine Transform). In the IJG code, this routine - * must also perform dequantization of the input coefficients. - * - * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT - * on each row (or vice versa, but it's more convenient to emit a row at - * a time). 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 jidctint.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. - * - * The dequantized coefficients are not integers because the AA&N scaling - * factors have been incorporated. We represent them scaled up by PASS1_BITS, - * so that the first and second IDCT rounds have the same input scaling. - * For 8-bit JSAMPLEs, we choose IFAST_SCALE_BITS = PASS1_BITS so as to - * avoid a descaling shift; this compromises accuracy rather drastically - * for small quantization table entries, but it saves a lot of shifts. - * For 12-bit JSAMPLEs, there's no hope of using 16x16 multiplies anyway, - * so we use a much larger scaling factor to preserve accuracy. - * - * 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). - */ - -#if BITS_IN_JSAMPLE == 8 -#define CONST_BITS 8 -#define PASS1_BITS 2 -#else -#define CONST_BITS 8 -#define PASS1_BITS 1 /* lose a little precision to avoid overflow */ -#endif - -/* 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_1_082392200 ((INT32) 277) /* FIX(1.082392200) */ -#define FIX_1_414213562 ((INT32) 362) /* FIX(1.414213562) */ -#define FIX_1_847759065 ((INT32) 473) /* FIX(1.847759065) */ -#define FIX_2_613125930 ((INT32) 669) /* FIX(2.613125930) */ -#else -#define FIX_1_082392200 FIX(1.082392200) -#define FIX_1_414213562 FIX(1.414213562) -#define FIX_1_847759065 FIX(1.847759065) -#define FIX_2_613125930 FIX(2.613125930) -#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)) - - -/* Dequantize a coefficient by multiplying it by the multiplier-table - * entry; produce a DCTELEM result. For 8-bit data a 16x16->16 - * multiplication will do. For 12-bit data, the multiplier table is - * declared INT32, so a 32-bit multiply will be used. - */ - -#if BITS_IN_JSAMPLE == 8 -#define DEQUANTIZE(coef,quantval) (((IFAST_MULT_TYPE) (coef)) * (quantval)) -#else -#define DEQUANTIZE(coef,quantval) \ - DESCALE((coef)*(quantval), IFAST_SCALE_BITS-PASS1_BITS) -#endif - - -/* Like DESCALE, but applies to a DCTELEM and produces an int. - * We assume that int right shift is unsigned if INT32 right shift is. - */ - -#ifdef RIGHT_SHIFT_IS_UNSIGNED -#define ISHIFT_TEMPS DCTELEM ishift_temp; -#if BITS_IN_JSAMPLE == 8 -#define DCTELEMBITS 16 /* DCTELEM may be 16 or 32 bits */ -#else -#define DCTELEMBITS 32 /* DCTELEM must be 32 bits */ -#endif -#define IRIGHT_SHIFT(x,shft) \ - ((ishift_temp = (x)) < 0 ? \ - (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \ - (ishift_temp >> (shft))) -#else -#define ISHIFT_TEMPS -#define IRIGHT_SHIFT(x,shft) ((x) >> (shft)) -#endif - -#ifdef USE_ACCURATE_ROUNDING -#define IDESCALE(x,n) ((int) IRIGHT_SHIFT((x) + (1 << ((n)-1)), n)) -#else -#define IDESCALE(x,n) ((int) IRIGHT_SHIFT(x, n)) -#endif - - -/* - * Perform dequantization and inverse DCT on one block of coefficients. - */ - -GLOBAL(void) -jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr, - JCOEFPTR coef_block, - JSAMPARRAY output_buf, JDIMENSION output_col) -{ - DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; - DCTELEM tmp10, tmp11, tmp12, tmp13; - DCTELEM z5, z10, z11, z12, z13; - JCOEFPTR inptr; - IFAST_MULT_TYPE * quantptr; - int * wsptr; - JSAMPROW outptr; - JSAMPLE *range_limit = IDCT_range_limit(cinfo); - int ctr; - int workspace[DCTSIZE2]; /* buffers data between passes */ - SHIFT_TEMPS /* for DESCALE */ - ISHIFT_TEMPS /* for IDESCALE */ - - /* Pass 1: process columns from input, store into work array. */ - - inptr = coef_block; - quantptr = (IFAST_MULT_TYPE *) compptr->dct_table; - wsptr = workspace; - for (ctr = DCTSIZE; ctr > 0; ctr--) { - /* Due to quantization, we will usually find that many of the input - * coefficients are zero, especially the AC terms. We can exploit this - * by short-circuiting the IDCT calculation for any column in which all - * the AC terms are zero. In that case each output is equal to the - * DC coefficient (with scale factor as needed). - * With typical images and quantization tables, half or more of the - * column DCT calculations can be simplified this way. - */ - - if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 && - inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 && - inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 && - inptr[DCTSIZE*7] == 0) { - /* AC terms all zero */ - int dcval = (int) DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); - - wsptr[DCTSIZE*0] = dcval; - wsptr[DCTSIZE*1] = dcval; - wsptr[DCTSIZE*2] = dcval; - wsptr[DCTSIZE*3] = dcval; - 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 */ - - tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); - tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); - tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]); - tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); - - tmp10 = tmp0 + tmp2; /* phase 3 */ - tmp11 = tmp0 - tmp2; - - tmp13 = tmp1 + tmp3; /* phases 5-3 */ - tmp12 = MULTIPLY(tmp1 - tmp3, FIX_1_414213562) - tmp13; /* 2*c4 */ - - tmp0 = tmp10 + tmp13; /* phase 2 */ - tmp3 = tmp10 - tmp13; - tmp1 = tmp11 + tmp12; - tmp2 = tmp11 - tmp12; - - /* Odd part */ - - tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); - tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); - tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); - tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); - - z13 = tmp6 + tmp5; /* phase 6 */ - z10 = tmp6 - tmp5; - z11 = tmp4 + tmp7; - z12 = tmp4 - tmp7; - - tmp7 = z11 + z13; /* phase 5 */ - tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */ - - z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */ - tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */ - tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */ - - tmp6 = tmp12 - tmp7; /* phase 2 */ - tmp5 = tmp11 - tmp6; - tmp4 = tmp10 + tmp5; - - wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7); - wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7); - wsptr[DCTSIZE*1] = (int) (tmp1 + tmp6); - wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6); - wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5); - wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5); - wsptr[DCTSIZE*4] = (int) (tmp3 + tmp4); - wsptr[DCTSIZE*3] = (int) (tmp3 - tmp4); - - 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] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 && - wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { - /* AC terms all zero */ - JSAMPLE dcval = range_limit[IDESCALE(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 */ - - tmp10 = ((DCTELEM) wsptr[0] + (DCTELEM) wsptr[4]); - tmp11 = ((DCTELEM) wsptr[0] - (DCTELEM) wsptr[4]); - - tmp13 = ((DCTELEM) wsptr[2] + (DCTELEM) wsptr[6]); - tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6], FIX_1_414213562) - - tmp13; - - tmp0 = tmp10 + tmp13; - tmp3 = tmp10 - tmp13; - tmp1 = tmp11 + tmp12; - tmp2 = tmp11 - tmp12; - - /* Odd part */ - - z13 = (DCTELEM) wsptr[5] + (DCTELEM) wsptr[3]; - z10 = (DCTELEM) wsptr[5] - (DCTELEM) wsptr[3]; - z11 = (DCTELEM) wsptr[1] + (DCTELEM) wsptr[7]; - z12 = (DCTELEM) wsptr[1] - (DCTELEM) wsptr[7]; - - tmp7 = z11 + z13; /* phase 5 */ - tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */ - - z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */ - tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */ - tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */ - - tmp6 = tmp12 - tmp7; /* phase 2 */ - tmp5 = tmp11 - tmp6; - tmp4 = tmp10 + tmp5; - - /* Final output stage: scale down by a factor of 8 and range-limit */ - - outptr[0] = range_limit[IDESCALE(tmp0 + tmp7, PASS1_BITS+3) - & RANGE_MASK]; - outptr[7] = range_limit[IDESCALE(tmp0 - tmp7, PASS1_BITS+3) - & RANGE_MASK]; - outptr[1] = range_limit[IDESCALE(tmp1 + tmp6, PASS1_BITS+3) - & RANGE_MASK]; - outptr[6] = range_limit[IDESCALE(tmp1 - tmp6, PASS1_BITS+3) - & RANGE_MASK]; - outptr[2] = range_limit[IDESCALE(tmp2 + tmp5, PASS1_BITS+3) - & RANGE_MASK]; - outptr[5] = range_limit[IDESCALE(tmp2 - tmp5, PASS1_BITS+3) - & RANGE_MASK]; - outptr[4] = range_limit[IDESCALE(tmp3 + tmp4, PASS1_BITS+3) - & RANGE_MASK]; - outptr[3] = range_limit[IDESCALE(tmp3 - tmp4, PASS1_BITS+3) - & RANGE_MASK]; - - wsptr += DCTSIZE; /* advance pointer to next row */ - } -} - -#endif /* DCT_IFAST_SUPPORTED */ |