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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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10
src/dsp/rescaler_mips_dsp_r2.c
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@ -20,10 +20,12 @@
#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)
//------------------------------------------------------------------------------
// Row export
#if 0 // disabled for now. TODO(skal): make match the C-code
static void ExportRowShrink_MIPSdspR2(WebPRescaler* const wrk) {
int i;
const int x_out_max = wrk->dst_width * wrk->num_channels;
@ -106,7 +108,7 @@ static void ExportRowShrink_MIPSdspR2(WebPRescaler* const wrk) {
}
for (i = 0; i < (x_out_max & 0x3); ++i) {
const uint32_t frac = (uint32_t)MULT_FIX(*frow++, yscale);
const int v = (int)MULT_FIX(*irow - frac, wrk->fxy_scale);
const int v = (int)MULT_FIX_FLOOR(*irow - frac, wrk->fxy_scale);
assert(v >= 0 && v <= 255);
*dst++ = v;
*irow++ = frac; // new fractional start
@ -154,13 +156,14 @@ static void ExportRowShrink_MIPSdspR2(WebPRescaler* const wrk) {
);
}
for (i = 0; i < (x_out_max & 0x3); ++i) {
const int v = (int)MULT_FIX(*irow, wrk->fxy_scale);
const int v = (int)MULT_FIX_FLOOR(*irow, wrk->fxy_scale);
assert(v >= 0 && v <= 255);
*dst++ = v;
*irow++ = 0;
}
}
}
#endif // 0
static void ExportRowExpand_MIPSdspR2(WebPRescaler* const wrk) {
int i;
@ -294,6 +297,7 @@ static void ExportRowExpand_MIPSdspR2(WebPRescaler* const wrk) {
}
}
#undef MULT_FIX_FLOOR
#undef MULT_FIX
#undef ROUNDER
@ -304,7 +308,7 @@ extern void WebPRescalerDspInitMIPSdspR2(void);
WEBP_TSAN_IGNORE_FUNCTION void WebPRescalerDspInitMIPSdspR2(void) {
WebPRescalerExportRowExpand = ExportRowExpand_MIPSdspR2;
WebPRescalerExportRowShrink = ExportRowShrink_MIPSdspR2;
// WebPRescalerExportRowShrink = ExportRowShrink_MIPSdspR2;
}
#else // !WEBP_USE_MIPS_DSP_R2