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fix rescaling rounding inaccuracy

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We should be using 'floor' when doing the final divide.

-> new MACRO is MULT_FIX_FLOOR()

     XXX*** Mips code is DISABLED for now ***XXX

I'll update and re-enable it in a later
patch, since this code needs some refactoring first.

BUG=oss-fuzz:9179

Change-Id: Ic0693cdca4e71f5beab1029475e35c4d06b12d13
This commit is contained in:
Pascal Massimino
2018-07-10 17:27:21 -07:00
committed by James Zern
parent 211f37ee63
commit 2563db4759
6 changed files with 65 additions and 13 deletions
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7
src/dsp/rescaler_msa.c
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@ -22,6 +22,7 @@
#define ROUNDER (WEBP_RESCALER_ONE >> 1)
#define MULT_FIX(x, y) (((uint64_t)(x) * (y) + ROUNDER) >> WEBP_RESCALER_RFIX)
#define MULT_FIX_FLOOR(x, y) (((uint64_t)(x) * (y)) >> WEBP_RESCALER_RFIX)
#define CALC_MULT_FIX_16(in0, in1, in2, in3, scale, shift, dst) do { \
v4u32 tmp0, tmp1, tmp2, tmp3; \
@ -262,6 +263,7 @@ static void RescalerExportRowExpand_MIPSdspR2(WebPRescaler* const wrk) {
}
}
#if 0 // disabled for now. TODO(skal): make match the C-code
static WEBP_INLINE void ExportRowShrink_0(const uint32_t* frow, uint32_t* irow,
uint8_t* dst, int length,
const uint32_t yscale,
@ -341,7 +343,7 @@ static WEBP_INLINE void ExportRowShrink_0(const uint32_t* frow, uint32_t* irow,
}
for (x_out = 0; x_out < length; ++x_out) {
const uint32_t frac = (uint32_t)MULT_FIX(frow[x_out], yscale);
const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
const int v = (int)MULT_FIX_FLOOR(irow[x_out] - frac, wrk->fxy_scale);
assert(v >= 0 && v <= 255);
dst[x_out] = v;
irow[x_out] = frac;
@ -426,6 +428,7 @@ static void RescalerExportRowShrink_MIPSdspR2(WebPRescaler* const wrk) {
ExportRowShrink_1(irow, dst, x_out_max, wrk);
}
}
#endif // 0
//------------------------------------------------------------------------------
// Entry point
@ -434,7 +437,7 @@ extern void WebPRescalerDspInitMSA(void);
WEBP_TSAN_IGNORE_FUNCTION void WebPRescalerDspInitMSA(void) {
WebPRescalerExportRowExpand = RescalerExportRowExpand_MIPSdspR2;
WebPRescalerExportRowShrink = RescalerExportRowShrink_MIPSdspR2;
// WebPRescalerExportRowShrink = RescalerExportRowShrink_MIPSdspR2;
}
#else // !WEBP_USE_MSA