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Diffstat (limited to 'src/jpeg-6b/jidctint.c')
| -rw-r--r-- | src/jpeg-6b/jidctint.c | 389 |
1 files changed, 0 insertions, 389 deletions
diff --git a/src/jpeg-6b/jidctint.c b/src/jpeg-6b/jidctint.c deleted file mode 100644 index a72b3207..00000000 --- a/src/jpeg-6b/jidctint.c +++ /dev/null @@ -1,389 +0,0 @@ -/* - * jidctint.c - * - * Copyright (C) 1991-1998, 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 slow-but-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 an algorithm described in - * C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT - * Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics, - * Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991. - * The primary algorithm described there uses 11 multiplies and 29 adds. - * We use their alternate method with 12 multiplies and 32 adds. - * The advantage of this method is that no data path contains more than one - * multiplication; this allows a very simple and accurate implementation in - * scaled fixed-point arithmetic, with a minimal number of shifts. - */ - -#define JPEG_INTERNALS -#include "jinclude.h" -#include "jpeglib.h" -#include "jdct.h" /* Private declarations for DCT subsystem */ - -#ifdef DCT_ISLOW_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 - - -/* - * The poop on this scaling stuff is as follows: - * - * Each 1-D IDCT step produces outputs which are a factor of sqrt(N) - * larger than the true IDCT outputs. The final outputs are therefore - * a factor of N larger than desired; since N=8 this can be cured by - * a simple right shift at the end of the algorithm. The advantage of - * this arrangement is that we save two multiplications per 1-D IDCT, - * because the y0 and y4 inputs need not be divided by sqrt(N). - * - * We have to do addition and subtraction of the integer inputs, which - * is no problem, and multiplication by fractional constants, which is - * a problem to do in integer arithmetic. We multiply all the constants - * by CONST_SCALE and convert them to integer constants (thus retaining - * CONST_BITS bits of precision in the constants). After doing a - * multiplication we have to divide the product by CONST_SCALE, with proper - * rounding, to produce the correct output. This division can be done - * cheaply as a right shift of CONST_BITS bits. We postpone shifting - * as long as possible so that partial sums can be added together with - * full fractional precision. - * - * The outputs of the first pass are scaled up by PASS1_BITS bits so that - * they are represented to better-than-integral precision. These outputs - * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word - * with the recommended scaling. (To scale up 12-bit sample data further, an - * intermediate INT32 array would be needed.) - * - * To avoid overflow of the 32-bit intermediate results in pass 2, we must - * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26. Error analysis - * shows that the values given below are the most effective. - */ - -#if BITS_IN_JSAMPLE == 8 -#define CONST_BITS 13 -#define PASS1_BITS 2 -#else -#define CONST_BITS 13 -#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 == 13 -#define FIX_0_298631336 ((INT32) 2446) /* FIX(0.298631336) */ -#define FIX_0_390180644 ((INT32) 3196) /* FIX(0.390180644) */ -#define FIX_0_541196100 ((INT32) 4433) /* FIX(0.541196100) */ -#define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */ -#define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */ -#define FIX_1_175875602 ((INT32) 9633) /* FIX(1.175875602) */ -#define FIX_1_501321110 ((INT32) 12299) /* FIX(1.501321110) */ -#define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */ -#define FIX_1_961570560 ((INT32) 16069) /* FIX(1.961570560) */ -#define FIX_2_053119869 ((INT32) 16819) /* FIX(2.053119869) */ -#define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */ -#define FIX_3_072711026 ((INT32) 25172) /* FIX(3.072711026) */ -#else -#define FIX_0_298631336 FIX(0.298631336) -#define FIX_0_390180644 FIX(0.390180644) -#define FIX_0_541196100 FIX(0.541196100) -#define FIX_0_765366865 FIX(0.765366865) -#define FIX_0_899976223 FIX(0.899976223) -#define FIX_1_175875602 FIX(1.175875602) -#define FIX_1_501321110 FIX(1.501321110) -#define FIX_1_847759065 FIX(1.847759065) -#define FIX_1_961570560 FIX(1.961570560) -#define FIX_2_053119869 FIX(2.053119869) -#define FIX_2_562915447 FIX(2.562915447) -#define FIX_3_072711026 FIX(3.072711026) -#endif - - -/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result. - * For 8-bit samples with the recommended scaling, all the variable - * and constant values involved are no more than 16 bits wide, so a - * 16x16->32 bit multiply can be used instead of a full 32x32 multiply. - * For 12-bit samples, a full 32-bit multiplication will be needed. - */ - -#if BITS_IN_JSAMPLE == 8 -#define MULTIPLY(var,const) MULTIPLY16C16(var,const) -#else -#define MULTIPLY(var,const) ((var) * (const)) -#endif - - -/* Dequantize a coefficient by multiplying it by the multiplier-table - * entry; produce an int result. In this module, both inputs and result - * are 16 bits or less, so either int or short multiply will work. - */ - -#define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval)) - - -/* - * Perform dequantization and inverse DCT on one block of coefficients. - */ - -GLOBAL(void) -jpeg_idct_islow (j_decompress_ptr cinfo, jpeg_component_info * compptr, - JCOEFPTR coef_block, - JSAMPARRAY output_buf, JDIMENSION output_col) -{ - INT32 tmp0, tmp1, tmp2, tmp3; - INT32 tmp10, tmp11, tmp12, tmp13; - INT32 z1, z2, z3, z4, z5; - JCOEFPTR inptr; - ISLOW_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 - - /* Pass 1: process columns from input, store into work array. */ - /* Note results are scaled up by sqrt(8) compared to a true IDCT; */ - /* furthermore, we scale the results by 2**PASS1_BITS. */ - - inptr = coef_block; - quantptr = (ISLOW_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 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS; - - 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: 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] == 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[(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 /* DCT_ISLOW_SUPPORTED */ |