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Rescaler: fix rounding error

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We saturate the result to [0..255]
It's the easiest and safest, given the wide variety of scaling
range we cover: we're not using floats, so precision is always
an issue at one end or the other of the scaling spectrum.

we also use:
  round(a - floor(b))
instead of:
  floor(a - round(b))
to handle difficult cases (ratio ~= .99, e.g.)

MIPS code is still disabled (and wrong)

Change-Id: I18d3f5ddc4c524879c257b928329b1c648fa7fb5
This commit is contained in:
Pascal Massimino 2019-03-28 19:44:39 +01:00
parent aa65f89a8f
commit ab2dc8939f
5 changed files with 43 additions and 97 deletions
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16
src/dsp/rescaler.c
View File

@ -109,8 +109,7 @@ void WebPRescalerExportRowExpand_C(WebPRescaler* const wrk) {
for (x_out = 0; x_out < x_out_max; ++x_out) { for (x_out = 0; x_out < x_out_max; ++x_out) {
const uint32_t J = frow[x_out]; const uint32_t J = frow[x_out];
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} else { } else {
const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub); const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub);
@ -120,8 +119,7 @@ void WebPRescalerExportRowExpand_C(WebPRescaler* const wrk) {
+ (uint64_t)B * irow[x_out]; + (uint64_t)B * irow[x_out];
const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX); const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX);
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} }
} }
@ -138,17 +136,15 @@ void WebPRescalerExportRowShrink_C(WebPRescaler* const wrk) {
assert(!wrk->y_expand); assert(!wrk->y_expand);
if (yscale) { if (yscale) {
for (x_out = 0; x_out < x_out_max; ++x_out) { for (x_out = 0; x_out < x_out_max; ++x_out) {
const uint32_t frac = (uint32_t)MULT_FIX(frow[x_out], yscale); const uint32_t frac = (uint32_t)MULT_FIX_FLOOR(frow[x_out], yscale);
const int v = (int)MULT_FIX_FLOOR(irow[x_out] - frac, wrk->fxy_scale); const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = frac; // new fractional start irow[x_out] = frac; // new fractional start
} }
} else { } else {
for (x_out = 0; x_out < x_out_max; ++x_out) { for (x_out = 0; x_out < x_out_max; ++x_out) {
const int v = (int)MULT_FIX(irow[x_out], wrk->fxy_scale); const int v = (int)MULT_FIX(irow[x_out], wrk->fxy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = 0; irow[x_out] = 0;
} }
} }

16
src/dsp/rescaler_mips_dsp_r2.c
View File

@ -107,10 +107,9 @@ static void ExportRowShrink_MIPSdspR2(WebPRescaler* const wrk) {
); );
} }
for (i = 0; i < (x_out_max & 0x3); ++i) { for (i = 0; i < (x_out_max & 0x3); ++i) {
const uint32_t frac = (uint32_t)MULT_FIX(*frow++, yscale); const uint32_t frac = (uint32_t)MULT_FIX_FLOOR(*frow++, yscale);
const int v = (int)MULT_FIX_FLOOR(*irow - frac, wrk->fxy_scale); const int v = (int)MULT_FIX(*irow - frac, wrk->fxy_scale);
assert(v >= 0 && v <= 255); *dst++ = (v > 255) ? 255u : (uint8_t)v;
*dst++ = v;
*irow++ = frac; // new fractional start *irow++ = frac; // new fractional start
} }
} else { } else {
@ -157,8 +156,7 @@ static void ExportRowShrink_MIPSdspR2(WebPRescaler* const wrk) {
} }
for (i = 0; i < (x_out_max & 0x3); ++i) { for (i = 0; i < (x_out_max & 0x3); ++i) {
const int v = (int)MULT_FIX_FLOOR(*irow, wrk->fxy_scale); const int v = (int)MULT_FIX_FLOOR(*irow, wrk->fxy_scale);
assert(v >= 0 && v <= 255); *dst++ = (v > 255) ? 255u : (uint8_t)v;
*dst++ = v;
*irow++ = 0; *irow++ = 0;
} }
} }
@ -219,8 +217,7 @@ static void ExportRowExpand_MIPSdspR2(WebPRescaler* const wrk) {
for (i = 0; i < (x_out_max & 0x3); ++i) { for (i = 0; i < (x_out_max & 0x3); ++i) {
const uint32_t J = *frow++; const uint32_t J = *frow++;
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); *dst++ = (v > 255) ? 255u : (uint8_t)v;
*dst++ = v;
} }
} else { } else {
const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub); const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub);
@ -291,8 +288,7 @@ static void ExportRowExpand_MIPSdspR2(WebPRescaler* const wrk) {
+ (uint64_t)B * *irow++; + (uint64_t)B * *irow++;
const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX); const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX);
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); *dst++ = (v > 255) ? 255u : (uint8_t)v;
*dst++ = v;
} }
} }
} }

16
src/dsp/rescaler_msa.c
View File

@ -166,8 +166,7 @@ static WEBP_INLINE void ExportRowExpand_0(const uint32_t* frow, uint8_t* dst,
for (x_out = 0; x_out < length; ++x_out) { for (x_out = 0; x_out < length; ++x_out) {
const uint32_t J = frow[x_out]; const uint32_t J = frow[x_out];
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} }
} }
@ -241,8 +240,7 @@ static WEBP_INLINE void ExportRowExpand_1(const uint32_t* frow, uint32_t* irow,
+ (uint64_t)B * irow[x_out]; + (uint64_t)B * irow[x_out];
const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX); const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX);
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} }
} }
@ -342,10 +340,9 @@ static WEBP_INLINE void ExportRowShrink_0(const uint32_t* frow, uint32_t* irow,
length -= 4; length -= 4;
} }
for (x_out = 0; x_out < length; ++x_out) { for (x_out = 0; x_out < length; ++x_out) {
const uint32_t frac = (uint32_t)MULT_FIX(frow[x_out], yscale); const uint32_t frac = (uint32_t)MULT_FIX_FLOOR(frow[x_out], yscale);
const int v = (int)MULT_FIX_FLOOR(irow[x_out] - frac, wrk->fxy_scale); const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = frac; irow[x_out] = frac;
} }
} }
@ -406,8 +403,7 @@ static WEBP_INLINE void ExportRowShrink_1(uint32_t* irow, uint8_t* dst,
} }
for (x_out = 0; x_out < length; ++x_out) { for (x_out = 0; x_out < length; ++x_out) {
const int v = (int)MULT_FIX(irow[x_out], wrk->fxy_scale); const int v = (int)MULT_FIX(irow[x_out], wrk->fxy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = 0; irow[x_out] = 0;
} }
} }

32
src/dsp/rescaler_neon.c
View File

@ -81,14 +81,13 @@ static void RescalerExportRowExpand_NEON(WebPRescaler* const wrk) {
const uint32x4_t B1 = MULT_FIX(A1, fy_scale_half); const uint32x4_t B1 = MULT_FIX(A1, fy_scale_half);
const uint16x4_t C0 = vmovn_u32(B0); const uint16x4_t C0 = vmovn_u32(B0);
const uint16x4_t C1 = vmovn_u32(B1); const uint16x4_t C1 = vmovn_u32(B1);
const uint8x8_t D = vmovn_u16(vcombine_u16(C0, C1)); const uint8x8_t D = vqmovn_u16(vcombine_u16(C0, C1));
vst1_u8(dst + x_out, D); vst1_u8(dst + x_out, D);
} }
for (; x_out < x_out_max; ++x_out) { for (; x_out < x_out_max; ++x_out) {
const uint32_t J = frow[x_out]; const uint32_t J = frow[x_out];
const int v = (int)MULT_FIX_C(J, fy_scale); const int v = (int)MULT_FIX_C(J, fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} else { } else {
const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub); const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub);
@ -102,7 +101,7 @@ static void RescalerExportRowExpand_NEON(WebPRescaler* const wrk) {
const uint32x4_t D1 = MULT_FIX(C1, fy_scale_half); const uint32x4_t D1 = MULT_FIX(C1, fy_scale_half);
const uint16x4_t E0 = vmovn_u32(D0); const uint16x4_t E0 = vmovn_u32(D0);
const uint16x4_t E1 = vmovn_u32(D1); const uint16x4_t E1 = vmovn_u32(D1);
const uint8x8_t F = vmovn_u16(vcombine_u16(E0, E1)); const uint8x8_t F = vqmovn_u16(vcombine_u16(E0, E1));
vst1_u8(dst + x_out, F); vst1_u8(dst + x_out, F);
} }
for (; x_out < x_out_max; ++x_out) { for (; x_out < x_out_max; ++x_out) {
@ -110,8 +109,7 @@ static void RescalerExportRowExpand_NEON(WebPRescaler* const wrk) {
+ (uint64_t)B * irow[x_out]; + (uint64_t)B * irow[x_out];
const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX); const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX);
const int v = (int)MULT_FIX_C(J, fy_scale); const int v = (int)MULT_FIX_C(J, fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} }
} }
@ -135,23 +133,22 @@ static void RescalerExportRowShrink_NEON(WebPRescaler* const wrk) {
for (x_out = 0; x_out < max_span; x_out += 8) { for (x_out = 0; x_out < max_span; x_out += 8) {
LOAD_32x8(frow + x_out, in0, in1); LOAD_32x8(frow + x_out, in0, in1);
LOAD_32x8(irow + x_out, in2, in3); LOAD_32x8(irow + x_out, in2, in3);
const uint32x4_t A0 = MULT_FIX(in0, yscale_half); const uint32x4_t A0 = MULT_FIX_FLOOR(in0, yscale_half);
const uint32x4_t A1 = MULT_FIX(in1, yscale_half); const uint32x4_t A1 = MULT_FIX_FLOOR(in1, yscale_half);
const uint32x4_t B0 = vqsubq_u32(in2, A0); const uint32x4_t B0 = vqsubq_u32(in2, A0);
const uint32x4_t B1 = vqsubq_u32(in3, A1); const uint32x4_t B1 = vqsubq_u32(in3, A1);
const uint32x4_t C0 = MULT_FIX_FLOOR(B0, fxy_scale_half); const uint32x4_t C0 = MULT_FIX(B0, fxy_scale_half);
const uint32x4_t C1 = MULT_FIX_FLOOR(B1, fxy_scale_half); const uint32x4_t C1 = MULT_FIX(B1, fxy_scale_half);
const uint16x4_t D0 = vmovn_u32(C0); const uint16x4_t D0 = vmovn_u32(C0);
const uint16x4_t D1 = vmovn_u32(C1); const uint16x4_t D1 = vmovn_u32(C1);
const uint8x8_t E = vmovn_u16(vcombine_u16(D0, D1)); const uint8x8_t E = vqmovn_u16(vcombine_u16(D0, D1));
vst1_u8(dst + x_out, E); vst1_u8(dst + x_out, E);
STORE_32x8(A0, A1, irow + x_out); STORE_32x8(A0, A1, irow + x_out);
} }
for (; x_out < x_out_max; ++x_out) { for (; x_out < x_out_max; ++x_out) {
const uint32_t frac = (uint32_t)MULT_FIX_C(frow[x_out], yscale); const uint32_t frac = (uint32_t)MULT_FIX_FLOOR_C(frow[x_out], yscale);
const int v = (int)MULT_FIX_FLOOR_C(irow[x_out] - frac, fxy_scale); const int v = (int)MULT_FIX_C(irow[x_out] - frac, fxy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = frac; // new fractional start irow[x_out] = frac; // new fractional start
} }
} else { } else {
@ -161,14 +158,13 @@ static void RescalerExportRowShrink_NEON(WebPRescaler* const wrk) {
const uint32x4_t A1 = MULT_FIX(in1, fxy_scale_half); const uint32x4_t A1 = MULT_FIX(in1, fxy_scale_half);
const uint16x4_t B0 = vmovn_u32(A0); const uint16x4_t B0 = vmovn_u32(A0);
const uint16x4_t B1 = vmovn_u32(A1); const uint16x4_t B1 = vmovn_u32(A1);
const uint8x8_t C = vmovn_u16(vcombine_u16(B0, B1)); const uint8x8_t C = vqmovn_u16(vcombine_u16(B0, B1));
vst1_u8(dst + x_out, C); vst1_u8(dst + x_out, C);
STORE_32x8(zero, zero, irow + x_out); STORE_32x8(zero, zero, irow + x_out);
} }
for (; x_out < x_out_max; ++x_out) { for (; x_out < x_out_max; ++x_out) {
const int v = (int)MULT_FIX_C(irow[x_out], fxy_scale); const int v = (int)MULT_FIX_C(irow[x_out], fxy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = 0; irow[x_out] = 0;
} }
} }

60
src/dsp/rescaler_sse2.c
View File

@ -225,35 +225,6 @@ static WEBP_INLINE void ProcessRow_SSE2(const __m128i* const A0,
_mm_storel_epi64((__m128i*)dst, G); _mm_storel_epi64((__m128i*)dst, G);
} }
static WEBP_INLINE void ProcessRow_Floor_SSE2(const __m128i* const A0,
const __m128i* const A1,
const __m128i* const A2,
const __m128i* const A3,
const __m128i* const mult,
uint8_t* const dst) {
const __m128i mask = _mm_set_epi32(0xffffffffu, 0, 0xffffffffu, 0);
const __m128i B0 = _mm_mul_epu32(*A0, *mult);
const __m128i B1 = _mm_mul_epu32(*A1, *mult);
const __m128i B2 = _mm_mul_epu32(*A2, *mult);
const __m128i B3 = _mm_mul_epu32(*A3, *mult);
const __m128i D0 = _mm_srli_epi64(B0, WEBP_RESCALER_RFIX);
const __m128i D1 = _mm_srli_epi64(B1, WEBP_RESCALER_RFIX);
#if (WEBP_RESCALER_RFIX < 32)
const __m128i D2 =
_mm_and_si128(_mm_slli_epi64(B2, 32 - WEBP_RESCALER_RFIX), mask);
const __m128i D3 =
_mm_and_si128(_mm_slli_epi64(B3, 32 - WEBP_RESCALER_RFIX), mask);
#else
const __m128i D2 = _mm_and_si128(B2, mask);
const __m128i D3 = _mm_and_si128(B3, mask);
#endif
const __m128i E0 = _mm_or_si128(D0, D2);
const __m128i E1 = _mm_or_si128(D1, D3);
const __m128i F = _mm_packs_epi32(E0, E1);
const __m128i G = _mm_packus_epi16(F, F);
_mm_storel_epi64((__m128i*)dst, G);
}
static void RescalerExportRowExpand_SSE2(WebPRescaler* const wrk) { static void RescalerExportRowExpand_SSE2(WebPRescaler* const wrk) {
int x_out; int x_out;
uint8_t* const dst = wrk->dst; uint8_t* const dst = wrk->dst;
@ -274,8 +245,7 @@ static void RescalerExportRowExpand_SSE2(WebPRescaler* const wrk) {
for (; x_out < x_out_max; ++x_out) { for (; x_out < x_out_max; ++x_out) {
const uint32_t J = frow[x_out]; const uint32_t J = frow[x_out];
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} else { } else {
const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub); const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub);
@ -308,8 +278,7 @@ static void RescalerExportRowExpand_SSE2(WebPRescaler* const wrk) {
+ (uint64_t)B * irow[x_out]; + (uint64_t)B * irow[x_out];
const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX); const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX);
const int v = (int)MULT_FIX(J, wrk->fy_scale); const int v = (int)MULT_FIX(J, wrk->fy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
} }
} }
} }
@ -328,20 +297,15 @@ static void RescalerExportRowShrink_SSE2(WebPRescaler* const wrk) {
const int scale_xy = wrk->fxy_scale; const int scale_xy = wrk->fxy_scale;
const __m128i mult_xy = _mm_set_epi32(0, scale_xy, 0, scale_xy); const __m128i mult_xy = _mm_set_epi32(0, scale_xy, 0, scale_xy);
const __m128i mult_y = _mm_set_epi32(0, yscale, 0, yscale); const __m128i mult_y = _mm_set_epi32(0, yscale, 0, yscale);
const __m128i rounder = _mm_set_epi32(0, ROUNDER, 0, ROUNDER);
for (x_out = 0; x_out + 8 <= x_out_max; x_out += 8) { for (x_out = 0; x_out + 8 <= x_out_max; x_out += 8) {
__m128i A0, A1, A2, A3, B0, B1, B2, B3; __m128i A0, A1, A2, A3, B0, B1, B2, B3;
LoadDispatchAndMult_SSE2(irow + x_out, NULL, &A0, &A1, &A2, &A3); LoadDispatchAndMult_SSE2(irow + x_out, NULL, &A0, &A1, &A2, &A3);
LoadDispatchAndMult_SSE2(frow + x_out, &mult_y, &B0, &B1, &B2, &B3); LoadDispatchAndMult_SSE2(frow + x_out, &mult_y, &B0, &B1, &B2, &B3);
{ {
const __m128i C0 = _mm_add_epi64(B0, rounder); const __m128i D0 = _mm_srli_epi64(B0, WEBP_RESCALER_RFIX); // = frac
const __m128i C1 = _mm_add_epi64(B1, rounder); const __m128i D1 = _mm_srli_epi64(B1, WEBP_RESCALER_RFIX);
const __m128i C2 = _mm_add_epi64(B2, rounder); const __m128i D2 = _mm_srli_epi64(B2, WEBP_RESCALER_RFIX);
const __m128i C3 = _mm_add_epi64(B3, rounder); const __m128i D3 = _mm_srli_epi64(B3, WEBP_RESCALER_RFIX);
const __m128i D0 = _mm_srli_epi64(C0, WEBP_RESCALER_RFIX); // = frac
const __m128i D1 = _mm_srli_epi64(C1, WEBP_RESCALER_RFIX);
const __m128i D2 = _mm_srli_epi64(C2, WEBP_RESCALER_RFIX);
const __m128i D3 = _mm_srli_epi64(C3, WEBP_RESCALER_RFIX);
const __m128i E0 = _mm_sub_epi64(A0, D0); // irow[x] - frac const __m128i E0 = _mm_sub_epi64(A0, D0); // irow[x] - frac
const __m128i E1 = _mm_sub_epi64(A1, D1); const __m128i E1 = _mm_sub_epi64(A1, D1);
const __m128i E2 = _mm_sub_epi64(A2, D2); const __m128i E2 = _mm_sub_epi64(A2, D2);
@ -352,14 +316,13 @@ static void RescalerExportRowShrink_SSE2(WebPRescaler* const wrk) {
const __m128i G1 = _mm_or_si128(D1, F3); const __m128i G1 = _mm_or_si128(D1, F3);
_mm_storeu_si128((__m128i*)(irow + x_out + 0), G0); _mm_storeu_si128((__m128i*)(irow + x_out + 0), G0);
_mm_storeu_si128((__m128i*)(irow + x_out + 4), G1); _mm_storeu_si128((__m128i*)(irow + x_out + 4), G1);
ProcessRow_Floor_SSE2(&E0, &E1, &E2, &E3, &mult_xy, dst + x_out); ProcessRow_SSE2(&E0, &E1, &E2, &E3, &mult_xy, dst + x_out);
} }
} }
for (; x_out < x_out_max; ++x_out) { for (; x_out < x_out_max; ++x_out) {
const uint32_t frac = (int)MULT_FIX(frow[x_out], yscale); const uint32_t frac = (int)MULT_FIX_FLOOR(frow[x_out], yscale);
const int v = (int)MULT_FIX_FLOOR(irow[x_out] - frac, wrk->fxy_scale); const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = frac; // new fractional start irow[x_out] = frac; // new fractional start
} }
} else { } else {
@ -375,8 +338,7 @@ static void RescalerExportRowShrink_SSE2(WebPRescaler* const wrk) {
} }
for (; x_out < x_out_max; ++x_out) { for (; x_out < x_out_max; ++x_out) {
const int v = (int)MULT_FIX(irow[x_out], scale); const int v = (int)MULT_FIX(irow[x_out], scale);
assert(v >= 0 && v <= 255); dst[x_out] = (v > 255) ? 255u : (uint8_t)v;
dst[x_out] = v;
irow[x_out] = 0; irow[x_out] = 0;
} }
} }