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Diffstat (limited to 'src/jpeg-6/jidctred.c')
-rw-r--r-- | src/jpeg-6/jidctred.c | 397 |
1 files changed, 397 insertions, 0 deletions
diff --git a/src/jpeg-6/jidctred.c b/src/jpeg-6/jidctred.c new file mode 100644 index 0000000..019c339 --- /dev/null +++ b/src/jpeg-6/jidctred.c @@ -0,0 +1,397 @@ +/* + * jidctred.c + * + * Copyright (C) 1994, 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 inverse-DCT routines that produce reduced-size output: + * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block. + * + * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M) + * algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step + * with an 8-to-4 step that produces the four averages of two adjacent outputs + * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output). + * These steps were derived by computing the corresponding values at the end + * of the normal LL&M code, then simplifying as much as possible. + * + * 1x1 is trivial: just take the DC coefficient divided by 8. + * + * See jidctint.c for additional comments. + */ + +#define JPEG_INTERNALS +#include "jinclude.h" +#include "jpeglib.h" +#include "jdct.h" /* Private declarations for DCT subsystem */ + +#ifdef IDCT_SCALING_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 is the same as in jidctint.c. */ + +#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_211164243 ((INT32) 1730) /* FIX(0.211164243) */ +#define FIX_0_509795579 ((INT32) 4176) /* FIX(0.509795579) */ +#define FIX_0_601344887 ((INT32) 4926) /* FIX(0.601344887) */ +#define FIX_0_720959822 ((INT32) 5906) /* FIX(0.720959822) */ +#define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */ +#define FIX_0_850430095 ((INT32) 6967) /* FIX(0.850430095) */ +#define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */ +#define FIX_1_061594337 ((INT32) 8697) /* FIX(1.061594337) */ +#define FIX_1_272758580 ((INT32) 10426) /* FIX(1.272758580) */ +#define FIX_1_451774981 ((INT32) 11893) /* FIX(1.451774981) */ +#define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */ +#define FIX_2_172734803 ((INT32) 17799) /* FIX(2.172734803) */ +#define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */ +#define FIX_3_624509785 ((INT32) 29692) /* FIX(3.624509785) */ +#else +#define FIX_0_211164243 FIX(0.211164243) +#define FIX_0_509795579 FIX(0.509795579) +#define FIX_0_601344887 FIX(0.601344887) +#define FIX_0_720959822 FIX(0.720959822) +#define FIX_0_765366865 FIX(0.765366865) +#define FIX_0_850430095 FIX(0.850430095) +#define FIX_0_899976223 FIX(0.899976223) +#define FIX_1_061594337 FIX(1.061594337) +#define FIX_1_272758580 FIX(1.272758580) +#define FIX_1_451774981 FIX(1.451774981) +#define FIX_1_847759065 FIX(1.847759065) +#define FIX_2_172734803 FIX(2.172734803) +#define FIX_2_562915447 FIX(2.562915447) +#define FIX_3_624509785 FIX(3.624509785) +#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, + * producing a reduced-size 4x4 output block. + */ + +GLOBAL void +jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr, + JCOEFPTR coef_block, + JSAMPARRAY output_buf, JDIMENSION output_col) +{ + INT32 tmp0, tmp2, tmp10, tmp12; + INT32 z1, z2, z3, z4; + JCOEFPTR inptr; + ISLOW_MULT_TYPE * quantptr; + int * wsptr; + JSAMPROW outptr; + JSAMPLE *range_limit = IDCT_range_limit(cinfo); + int ctr; + int workspace[DCTSIZE*4]; /* buffers data between passes */ + SHIFT_TEMPS + + /* Pass 1: process columns from input, store into work array. */ + + inptr = coef_block; + quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; + wsptr = workspace; + for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { + /* Don't bother to process column 4, because second pass won't use it */ + if (ctr == DCTSIZE-4) + continue; + if ((inptr[DCTSIZE*1] | inptr[DCTSIZE*2] | inptr[DCTSIZE*3] | + inptr[DCTSIZE*5] | inptr[DCTSIZE*6] | inptr[DCTSIZE*7]) == 0) { + /* AC terms all zero; we need not examine term 4 for 4x4 output */ + 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; + + continue; + } + + /* Even part */ + + tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); + tmp0 <<= (CONST_BITS+1); + + z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]); + z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]); + + tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865); + + tmp10 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + + /* Odd part */ + + z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); + z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); + z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); + z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); + + tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ + + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ + + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ + + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ + + tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ + + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ + + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ + + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ + + /* Final output stage */ + + wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1); + wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1); + wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1); + wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1); + } + + /* Pass 2: process 4 rows from work array, store into output array. */ + + wsptr = workspace; + for (ctr = 0; ctr < 4; ctr++) { + outptr = output_buf[ctr] + output_col; + /* It's not clear whether a zero row test is worthwhile here ... */ + +#ifndef NO_ZERO_ROW_TEST + if ((wsptr[1] | wsptr[2] | wsptr[3] | wsptr[5] | wsptr[6] | + 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; + + wsptr += DCTSIZE; /* advance pointer to next row */ + continue; + } +#endif + + /* Even part */ + + tmp0 = ((INT32) wsptr[0]) << (CONST_BITS+1); + + tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065) + + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865); + + tmp10 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + + /* Odd part */ + + z1 = (INT32) wsptr[7]; + z2 = (INT32) wsptr[5]; + z3 = (INT32) wsptr[3]; + z4 = (INT32) wsptr[1]; + + tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */ + + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */ + + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */ + + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */ + + tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */ + + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */ + + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */ + + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */ + + /* Final output stage */ + + outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2, + CONST_BITS+PASS1_BITS+3+1) + & RANGE_MASK]; + outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2, + CONST_BITS+PASS1_BITS+3+1) + & RANGE_MASK]; + outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0, + CONST_BITS+PASS1_BITS+3+1) + & RANGE_MASK]; + outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0, + CONST_BITS+PASS1_BITS+3+1) + & RANGE_MASK]; + + wsptr += DCTSIZE; /* advance pointer to next row */ + } +} + + +/* + * Perform dequantization and inverse DCT on one block of coefficients, + * producing a reduced-size 2x2 output block. + */ + +GLOBAL void +jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr, + JCOEFPTR coef_block, + JSAMPARRAY output_buf, JDIMENSION output_col) +{ + INT32 tmp0, tmp10, z1; + JCOEFPTR inptr; + ISLOW_MULT_TYPE * quantptr; + int * wsptr; + JSAMPROW outptr; + JSAMPLE *range_limit = IDCT_range_limit(cinfo); + int ctr; + int workspace[DCTSIZE*2]; /* buffers data between passes */ + SHIFT_TEMPS + + /* Pass 1: process columns from input, store into work array. */ + + inptr = coef_block; + quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; + wsptr = workspace; + for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) { + /* Don't bother to process columns 2,4,6 */ + if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6) + continue; + if ((inptr[DCTSIZE*1] | inptr[DCTSIZE*3] | + inptr[DCTSIZE*5] | inptr[DCTSIZE*7]) == 0) { + /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */ + int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS; + + wsptr[DCTSIZE*0] = dcval; + wsptr[DCTSIZE*1] = dcval; + + continue; + } + + /* Even part */ + + z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]); + tmp10 = z1 << (CONST_BITS+2); + + /* Odd part */ + + z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]); + tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */ + z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]); + tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */ + z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]); + tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */ + z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]); + tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ + + /* Final output stage */ + + wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2); + wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2); + } + + /* Pass 2: process 2 rows from work array, store into output array. */ + + wsptr = workspace; + for (ctr = 0; ctr < 2; ctr++) { + outptr = output_buf[ctr] + output_col; + /* It's not clear whether a zero row test is worthwhile here ... */ + +#ifndef NO_ZERO_ROW_TEST + if ((wsptr[1] | wsptr[3] | wsptr[5] | 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; + + wsptr += DCTSIZE; /* advance pointer to next row */ + continue; + } +#endif + + /* Even part */ + + tmp10 = ((INT32) wsptr[0]) << (CONST_BITS+2); + + /* Odd part */ + + tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */ + + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */ + + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */ + + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */ + + /* Final output stage */ + + outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0, + CONST_BITS+PASS1_BITS+3+2) + & RANGE_MASK]; + outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0, + CONST_BITS+PASS1_BITS+3+2) + & RANGE_MASK]; + + wsptr += DCTSIZE; /* advance pointer to next row */ + } +} + + +/* + * Perform dequantization and inverse DCT on one block of coefficients, + * producing a reduced-size 1x1 output block. + */ + +GLOBAL void +jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr, + JCOEFPTR coef_block, + JSAMPARRAY output_buf, JDIMENSION output_col) +{ + int dcval; + ISLOW_MULT_TYPE * quantptr; + JSAMPLE *range_limit = IDCT_range_limit(cinfo); + SHIFT_TEMPS + + /* We hardly need an inverse DCT routine for this: just take the + * average pixel value, which is one-eighth of the DC coefficient. + */ + quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table; + dcval = DEQUANTIZE(coef_block[0], quantptr[0]); + dcval = (int) DESCALE((INT32) dcval, 3); + + output_buf[0][output_col] = range_limit[dcval & RANGE_MASK]; +} + +#endif /* IDCT_SCALING_SUPPORTED */ |