/* * jidctred.c * * Copyright (C) 1994-1998, Thomas G. Lane. * * ARM NEON optimizations * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). All rights reserved. * Contact: Alexander Bokovoy * * 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. */ #if defined(WITH_SIMD) && defined(__ARM_NEON__) && (BITS_IN_JSAMPLE == 8) /* ARM NEON optimized version of 'jpeg_idct_4x4' */ GLOBAL(void) jpeg_idct_4x4_neon (j_decompress_ptr cinfo, jpeg_component_info * compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col) { JCOEFPTR inptr = coef_block; ISLOW_MULT_TYPE * quantptr = compptr->dct_table; int tmp; const static short c[12] = { FIX_1_847759065, /* d0[0] */ -FIX_0_765366865, /* d0[1] */ -FIX_0_211164243, /* d0[2] */ FIX_1_451774981, /* d0[3] */ -FIX_2_172734803, /* d1[0] */ FIX_1_061594337, /* d1[1] */ -FIX_0_509795579, /* d1[2] */ -FIX_0_601344887, /* d1[3] */ FIX_0_899976223, /* d2[0] */ FIX_2_562915447, /* d2[1] */ 1 << (CONST_BITS+1), /* d2[2] */ 0}; /* d2[3] */ asm volatile ( /* load constants */ "vld1.16 {d0, d1, d2}, [%[c]]\n" /* load all coef block: * 0 | d4 d5 * 1 | d6 d7 * 2 | d8 d9 * 3 | d10 d11 * 4 | * 5 | d12 d13 * 6 | d14 d15 * 7 | d16 d17 */ "vld1.16 {d4, d5, d6, d7}, [%[inptr]]!\n" "vld1.16 {d8, d9, d10, d11}, [%[inptr]]!\n" "add %[inptr], %[inptr], #16\n" "vld1.16 {d12, d13, d14, d15}, [%[inptr]]!\n" "vld1.16 {d16, d17}, [%[inptr]]!\n" /* dequantize */ "vld1.16 {d18, d19, d20, d21}, [%[quantptr]]!\n" "vmul.s16 q2, q2, q9\n" "vld1.16 {d22, d23, d24, d25}, [%[quantptr]]!\n" "vmul.s16 q3, q3, q10\n" "vmul.s16 q4, q4, q11\n" "add %[quantptr], %[quantptr], #16\n" "vld1.16 {d26, d27, d28, d29}, [%[quantptr]]!\n" "vmul.s16 q5, q5, q12\n" "vmul.s16 q6, q6, q13\n" "vld1.16 {d30, d31}, [%[quantptr]]!\n" "vmul.s16 q7, q7, q14\n" "vmul.s16 q8, q8, q15\n" /* * tmp0 : q12 * tmp2 : q13 * tmp10 : q14 * tmp12 : q15 */ ".macro idct_helper x4, x6, x8, x10, x12, x14, x16, shift," " y26, y27, y28, y29\n" "vmull.s16 q14, \\x4, d2[2]\n" "vmlal.s16 q14, \\x8, d0[0]\n" "vmlal.s16 q14, \\x14, d0[1]\n" "vmull.s16 q13, \\x16, d1[2]\n" "vmlal.s16 q13, \\x12, d1[3]\n" "vmlal.s16 q13, \\x10, d2[0]\n" "vmlal.s16 q13, \\x6, d2[1]\n" "vmull.s16 q15, \\x4, d2[2]\n" "vmlsl.s16 q15, \\x8, d0[0]\n" "vmlsl.s16 q15, \\x14, d0[1]\n" "vmull.s16 q12, \\x16, d0[2]\n" "vmlal.s16 q12, \\x12, d0[3]\n" "vmlal.s16 q12, \\x10, d1[0]\n" "vmlal.s16 q12, \\x6, d1[1]\n" "vadd.s32 q10, q14, q13\n" "vsub.s32 q14, q14, q13\n" ".if \\shift > 16\n" " vrshr.s32 q10, q10, #\\shift\n" " vrshr.s32 q14, q14, #\\shift\n" " vmovn.s32 \\y26, q10\n" " vmovn.s32 \\y27, q14\n" ".else\n" " vrshrn.s32 \\y26, q10, #\\shift\n" " vrshrn.s32 \\y27, q14, #\\shift\n" ".endif\n" "vadd.s32 q10, q15, q12\n" "vsub.s32 q15, q15, q12\n" ".if \\shift > 16\n" " vrshr.s32 q10, q10, #\\shift\n" " vrshr.s32 q15, q15, #\\shift\n" " vmovn.s32 \\y28, q10\n" " vmovn.s32 \\y29, q15\n" ".else\n" " vrshrn.s32 \\y28, q10, #\\shift\n" " vrshrn.s32 \\y29, q15, #\\shift\n" ".endif\n" ".endm\n" /* do idct, transposing results after each step */ /* pass 1 */ "idct_helper d4, d6, d8, d10, d12, d14, d16, 12, d4, d6, d8, d10\n" "vtrn.16 d4, d8\n" "vtrn.16 d10, d6\n" "vtrn.32 d4, d10\n" "vtrn.32 d8, d6\n" "idct_helper d5, d7, d9, d11, d13, d15, d17, 12, d5, d7, d9, d11\n" "vtrn.16 d5, d9\n" "vtrn.16 d11, d7\n" "vtrn.32 d5, d11\n" "vtrn.32 d9, d7\n" /* pass 2 */ "idct_helper d4, d8, d10, d6, d9, d11, d7, 19, d26, d27, d28, d29\n" "vtrn.16 d26, d28\n" "vtrn.16 d29, d27\n" "vtrn.32 d26, d29\n" "vtrn.32 d28, d27\n" /* range limit */ "vmov.u16 q15, #0x80\n" "vadd.s16 q13, q13, q15\n" "vadd.s16 q14, q14, q15\n" "vqmovun.s16 d26, q13\n" "vqmovun.s16 d27, q14\n" /* store results to the output buffer */ "ldr %[tmp], [%[output_buf]], #4\n" "add %[tmp], %[tmp], %[output_col]\n" "vst1.8 {d26[0]}, [%[tmp]]!\n" "vst1.8 {d26[1]}, [%[tmp]]!\n" "vst1.8 {d26[2]}, [%[tmp]]!\n" "vst1.8 {d26[3]}, [%[tmp]]!\n" "ldr %[tmp], [%[output_buf]], #4\n" "add %[tmp], %[tmp], %[output_col]\n" "vst1.8 {d27[0]}, [%[tmp]]!\n" "vst1.8 {d27[1]}, [%[tmp]]!\n" "vst1.8 {d27[2]}, [%[tmp]]!\n" "vst1.8 {d27[3]}, [%[tmp]]!\n" "ldr %[tmp], [%[output_buf]], #4\n" "add %[tmp], %[tmp], %[output_col]\n" "vst1.8 {d27[4]}, [%[tmp]]!\n" "vst1.8 {d27[5]}, [%[tmp]]!\n" "vst1.8 {d27[6]}, [%[tmp]]!\n" "vst1.8 {d27[7]}, [%[tmp]]!\n" "ldr %[tmp], [%[output_buf]], #4\n" "add %[tmp], %[tmp], %[output_col]\n" "vst1.8 {d26[4]}, [%[tmp]]!\n" "vst1.8 {d26[5]}, [%[tmp]]!\n" "vst1.8 {d26[6]}, [%[tmp]]!\n" "vst1.8 {d26[7]}, [%[tmp]]!\n" : [inptr] "+&r" (inptr), [quantptr] "+&r" (quantptr), [tmp] "=&r" (tmp), [output_buf] "+&r" (output_buf) : [c] "r" (c), [output_col] "r" (output_col) : "cc", "memory", "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7", "d8", "d9", "d10", "d11", "d12", "d13", "d14", "d15", "d16", "d17", "d18", "d19", "d20", "d21", "d22", "d23", "d24", "d25", "d26", "d27", "d28", "d29", "d30", "d31"); } #if 0 /* * A slightly modified C code (which maps to NEON instructions better), * which was used as a reference implementation for converting to NEON. */ 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; short * wsptr; JSAMPROW outptr; JSAMPLE *range_limit = IDCT_range_limit(cinfo); int ctr; short workspace[DCTSIZE*8]; /* buffers data between passes */ JCOEF dequantized_input[DCTSIZE*8]; int i, tmp; SHIFT_TEMPS /* Pass 0: dequantize data. */ quantptr = compptr->dct_table; inptr = coef_block; for (ctr = 0; ctr < 64; ctr++) dequantized_input[ctr] = DEQUANTIZE(inptr[ctr], quantptr[ctr]); /* Pass 1: process columns from input, store into work array. */ inptr = dequantized_input; wsptr = workspace; for (ctr = DCTSIZE; ctr > 0; inptr++, wsptr+=DCTSIZE, ctr--) { /* Even part */ tmp10 = (inptr[DCTSIZE*0] << (CONST_BITS+1)) + MULTIPLY(inptr[DCTSIZE*2], FIX_1_847759065) + MULTIPLY(inptr[DCTSIZE*6], - FIX_0_765366865); tmp12 = (inptr[DCTSIZE*0] << (CONST_BITS+1)) - MULTIPLY(inptr[DCTSIZE*2], FIX_1_847759065) - MULTIPLY(inptr[DCTSIZE*6], - FIX_0_765366865); /* Odd part */ tmp0 = MULTIPLY(inptr[DCTSIZE*7], - FIX_0_211164243) + MULTIPLY(inptr[DCTSIZE*5], FIX_1_451774981) + MULTIPLY(inptr[DCTSIZE*3], - FIX_2_172734803) + MULTIPLY(inptr[DCTSIZE*1], FIX_1_061594337); tmp2 = MULTIPLY(inptr[DCTSIZE*7], - FIX_0_509795579) + MULTIPLY(inptr[DCTSIZE*5], - FIX_0_601344887) + MULTIPLY(inptr[DCTSIZE*3], FIX_0_899976223) + MULTIPLY(inptr[DCTSIZE*1], FIX_2_562915447); /* Final output stage */ wsptr[0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1); wsptr[3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1); wsptr[1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1); wsptr[2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1); } /* Pass 2: process 4 rows from work array, store into output array. */ inptr = workspace; for (ctr = 0; ctr < 4; ctr++, inptr++) { outptr = output_buf[ctr] + output_col; /* Even part */ tmp10 = (inptr[DCTSIZE*0] << (CONST_BITS+1)) + MULTIPLY(inptr[DCTSIZE*2], FIX_1_847759065) + MULTIPLY(inptr[DCTSIZE*6], - FIX_0_765366865); tmp12 = (inptr[DCTSIZE*0] << (CONST_BITS+1)) - MULTIPLY(inptr[DCTSIZE*2], FIX_1_847759065) - MULTIPLY(inptr[DCTSIZE*6], - FIX_0_765366865); /* Odd part */ tmp0 = MULTIPLY(inptr[DCTSIZE*7], - FIX_0_211164243) + MULTIPLY(inptr[DCTSIZE*5], FIX_1_451774981) + MULTIPLY(inptr[DCTSIZE*3], - FIX_2_172734803) + MULTIPLY(inptr[DCTSIZE*1], FIX_1_061594337); tmp2 = MULTIPLY(inptr[DCTSIZE*7], - FIX_0_509795579) + MULTIPLY(inptr[DCTSIZE*5], - FIX_0_601344887) + MULTIPLY(inptr[DCTSIZE*3], FIX_0_899976223) + MULTIPLY(inptr[DCTSIZE*1], FIX_2_562915447); /* 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]; } } #endif #else 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] == 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 = 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] == 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((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 */ } } #endif /* * 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] == 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 = 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] == 0 && wsptr[3] == 0 && wsptr[5] == 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; 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 */