| /* |
| * jidctred.c |
| * |
| * This file was part of the Independent JPEG Group's software. |
| * Copyright (C) 1994-1998, Thomas G. Lane. |
| * libjpeg-turbo Modifications: |
| * Copyright (C) 2015, D. R. Commander. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * 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 ((JLONG)1730) /* FIX(0.211164243) */ |
| #define FIX_0_509795579 ((JLONG)4176) /* FIX(0.509795579) */ |
| #define FIX_0_601344887 ((JLONG)4926) /* FIX(0.601344887) */ |
| #define FIX_0_720959822 ((JLONG)5906) /* FIX(0.720959822) */ |
| #define FIX_0_765366865 ((JLONG)6270) /* FIX(0.765366865) */ |
| #define FIX_0_850430095 ((JLONG)6967) /* FIX(0.850430095) */ |
| #define FIX_0_899976223 ((JLONG)7373) /* FIX(0.899976223) */ |
| #define FIX_1_061594337 ((JLONG)8697) /* FIX(1.061594337) */ |
| #define FIX_1_272758580 ((JLONG)10426) /* FIX(1.272758580) */ |
| #define FIX_1_451774981 ((JLONG)11893) /* FIX(1.451774981) */ |
| #define FIX_1_847759065 ((JLONG)15137) /* FIX(1.847759065) */ |
| #define FIX_2_172734803 ((JLONG)17799) /* FIX(2.172734803) */ |
| #define FIX_2_562915447 ((JLONG)20995) /* FIX(2.562915447) */ |
| #define FIX_3_624509785 ((JLONG)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 a JLONG variable by a JLONG constant to yield a JLONG 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) |
| { |
| JLONG tmp0, tmp2, tmp10, tmp12; |
| JLONG 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] == 0 && inptr[DCTSIZE * 2] == 0 && |
| inptr[DCTSIZE * 3] == 0 && inptr[DCTSIZE * 5] == 0 && |
| inptr[DCTSIZE * 6] == 0 && inptr[DCTSIZE * 7] == 0) { |
| /* AC terms all zero; we need not examine term 4 for 4x4 output */ |
| int dcval = LEFT_SHIFT(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 = LEFT_SHIFT(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] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && |
| wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) { |
| /* AC terms all zero */ |
| JSAMPLE dcval = range_limit[(int)DESCALE((JLONG)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 = LEFT_SHIFT((JLONG)wsptr[0], CONST_BITS + 1); |
| |
| tmp2 = MULTIPLY((JLONG)wsptr[2], FIX_1_847759065) + |
| MULTIPLY((JLONG)wsptr[6], -FIX_0_765366865); |
| |
| tmp10 = tmp0 + tmp2; |
| tmp12 = tmp0 - tmp2; |
| |
| /* Odd part */ |
| |
| z1 = (JLONG)wsptr[7]; |
| z2 = (JLONG)wsptr[5]; |
| z3 = (JLONG)wsptr[3]; |
| z4 = (JLONG)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) |
| { |
| JLONG 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] == 0 && inptr[DCTSIZE * 3] == 0 && |
| inptr[DCTSIZE * 5] == 0 && inptr[DCTSIZE * 7] == 0) { |
| /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */ |
| int dcval = LEFT_SHIFT(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 = LEFT_SHIFT(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] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) { |
| /* AC terms all zero */ |
| JSAMPLE dcval = range_limit[(int)DESCALE((JLONG)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 = LEFT_SHIFT((JLONG)wsptr[0], CONST_BITS + 2); |
| |
| /* Odd part */ |
| |
| tmp0 = MULTIPLY((JLONG)wsptr[7], -FIX_0_720959822) + /* sqrt(2) * ( c7-c5+c3-c1) */ |
| MULTIPLY((JLONG)wsptr[5], FIX_0_850430095) + /* sqrt(2) * (-c1+c3+c5+c7) */ |
| MULTIPLY((JLONG)wsptr[3], -FIX_1_272758580) + /* sqrt(2) * (-c1+c3-c5-c7) */ |
| MULTIPLY((JLONG)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((JLONG)dcval, 3); |
| |
| output_buf[0][output_col] = range_limit[dcval & RANGE_MASK]; |
| } |
| |
| #endif /* IDCT_SCALING_SUPPORTED */ |
