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modules/javafx.graphics/src/main/native-iio/libjpeg7/jidctflt.c
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@@ -1,9 +1,10 @@
/*
* jidctflt.c
*
* Copyright (C) 1994-1998, Thomas G. Lane.
+ * Modified 2010-2017 by Guido Vollbeding.
* 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 floating-point implementation of the
* inverse DCT (Discrete Cosine Transform). In the IJG code, this routine
@@ -47,11 +48,11 @@
/*
* This module is specialized to the case DCTSIZE = 8.
*/
#if DCTSIZE != 8
- Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
+ Sorry, this code only copes with 8x8 DCT blocks. /* deliberate syntax err */
#endif
/* Dequantize a coefficient by multiplying it by the multiplier-table
* entry; produce a float result.
@@ -60,10 +61,12 @@
#define DEQUANTIZE(coef,quantval) (((FAST_FLOAT) (coef)) * (quantval))
/*
* Perform dequantization and inverse DCT on one block of coefficients.
+ *
+ * cK represents cos(K*pi/16).
*/
GLOBAL(void)
jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
JCOEFPTR coef_block,
@@ -77,11 +80,10 @@
FAST_FLOAT * wsptr;
JSAMPROW outptr;
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
int ctr;
FAST_FLOAT workspace[DCTSIZE2]; /* buffers data between passes */
- SHIFT_TEMPS
/* Pass 1: process columns from input, store into work array. */
inptr = coef_block;
quantptr = (FLOAT_MULT_TYPE *) compptr->dct_table;
@@ -150,33 +152,32 @@
tmp7 = z11 + z13; /* phase 5 */
tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562); /* 2*c4 */
z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */
- tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */
- tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */
+ tmp10 = z5 - z12 * ((FAST_FLOAT) 1.082392200); /* 2*(c2-c6) */
+ tmp12 = z5 - z10 * ((FAST_FLOAT) 2.613125930); /* 2*(c2+c6) */
tmp6 = tmp12 - tmp7; /* phase 2 */
tmp5 = tmp11 - tmp6;
- tmp4 = tmp10 + tmp5;
+ tmp4 = tmp10 - tmp5;
wsptr[DCTSIZE*0] = tmp0 + tmp7;
wsptr[DCTSIZE*7] = tmp0 - tmp7;
wsptr[DCTSIZE*1] = tmp1 + tmp6;
wsptr[DCTSIZE*6] = tmp1 - tmp6;
wsptr[DCTSIZE*2] = tmp2 + tmp5;
wsptr[DCTSIZE*5] = tmp2 - tmp5;
- wsptr[DCTSIZE*4] = tmp3 + tmp4;
- wsptr[DCTSIZE*3] = tmp3 - tmp4;
+ wsptr[DCTSIZE*3] = tmp3 + tmp4;
+ wsptr[DCTSIZE*4] = 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. */
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.
@@ -185,15 +186,18 @@
* And testing floats for zero is relatively expensive, so we don't bother.
*/
/* Even part */
- tmp10 = wsptr[0] + wsptr[4];
- tmp11 = wsptr[0] - wsptr[4];
+ /* Prepare range-limit and float->int conversion */
+ z5 = wsptr[0] + (((FAST_FLOAT) RANGE_CENTER) + ((FAST_FLOAT) 0.5));
+ tmp10 = z5 + wsptr[4];
+ tmp11 = z5 - wsptr[4];
tmp13 = wsptr[2] + wsptr[6];
- tmp12 = (wsptr[2] - wsptr[6]) * ((FAST_FLOAT) 1.414213562) - tmp13;
+ tmp12 = (wsptr[2] - wsptr[6]) *
+ ((FAST_FLOAT) 1.414213562) - tmp13; /* 2*c4 */
tmp0 = tmp10 + tmp13;
tmp3 = tmp10 - tmp13;
tmp1 = tmp11 + tmp12;
tmp2 = tmp11 - tmp12;
@@ -203,39 +207,31 @@
z13 = wsptr[5] + wsptr[3];
z10 = wsptr[5] - wsptr[3];
z11 = wsptr[1] + wsptr[7];
z12 = wsptr[1] - wsptr[7];
- tmp7 = z11 + z13;
- tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562);
+ tmp7 = z11 + z13; /* phase 5 */
+ tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562); /* 2*c4 */
z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */
- tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */
- tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */
+ tmp10 = z5 - z12 * ((FAST_FLOAT) 1.082392200); /* 2*(c2-c6) */
+ tmp12 = z5 - z10 * ((FAST_FLOAT) 2.613125930); /* 2*(c2+c6) */
- tmp6 = tmp12 - tmp7;
+ tmp6 = tmp12 - tmp7; /* phase 2 */
tmp5 = tmp11 - tmp6;
- tmp4 = tmp10 + tmp5;
+ tmp4 = tmp10 - tmp5;
- /* Final output stage: scale down by a factor of 8 and range-limit */
+ /* Final output stage: float->int conversion and range-limit */
- outptr[0] = range_limit[(int) DESCALE((INT32) (tmp0 + tmp7), 3)
- & RANGE_MASK];
- outptr[7] = range_limit[(int) DESCALE((INT32) (tmp0 - tmp7), 3)
- & RANGE_MASK];
- outptr[1] = range_limit[(int) DESCALE((INT32) (tmp1 + tmp6), 3)
- & RANGE_MASK];
- outptr[6] = range_limit[(int) DESCALE((INT32) (tmp1 - tmp6), 3)
- & RANGE_MASK];
- outptr[2] = range_limit[(int) DESCALE((INT32) (tmp2 + tmp5), 3)
- & RANGE_MASK];
- outptr[5] = range_limit[(int) DESCALE((INT32) (tmp2 - tmp5), 3)
- & RANGE_MASK];
- outptr[4] = range_limit[(int) DESCALE((INT32) (tmp3 + tmp4), 3)
- & RANGE_MASK];
- outptr[3] = range_limit[(int) DESCALE((INT32) (tmp3 - tmp4), 3)
- & RANGE_MASK];
+ outptr[0] = range_limit[(int) (tmp0 + tmp7) & RANGE_MASK];
+ outptr[7] = range_limit[(int) (tmp0 - tmp7) & RANGE_MASK];
+ outptr[1] = range_limit[(int) (tmp1 + tmp6) & RANGE_MASK];
+ outptr[6] = range_limit[(int) (tmp1 - tmp6) & RANGE_MASK];
+ outptr[2] = range_limit[(int) (tmp2 + tmp5) & RANGE_MASK];
+ outptr[5] = range_limit[(int) (tmp2 - tmp5) & RANGE_MASK];
+ outptr[3] = range_limit[(int) (tmp3 + tmp4) & RANGE_MASK];
+ outptr[4] = range_limit[(int) (tmp3 - tmp4) & RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
}
}
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