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SIMD ColorLUT. Fix color overflow
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# Conflicts:
#	src/PIL/_version.py
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homm committed Sep 23, 2024
1 parent 2fb111d commit f5aa988
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Showing 4 changed files with 14 additions and 8 deletions.
6 changes: 5 additions & 1 deletion CHANGES.SIMD.rst
Original file line number Diff line number Diff line change
@@ -1,13 +1,17 @@
Changelog (Pillow-SIMD)
=======================

9.5.0.post2 & 9.4.0.post2 & 9.3.0.post2 & 9.2.0.post2 & 9.1.1.post2 & 9.0.0.post3
---------------------------------------------------------------------------------

- Fixed color ovrflow in LUT processing

9.0.0.post1
-----------

- Fixed possible overflow in LUT processing
- Restored compatibility with Visual C Compiler


7.0.0.post4
-----------

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2 changes: 1 addition & 1 deletion src/PIL/_version.py
Original file line number Diff line number Diff line change
@@ -1,2 +1,2 @@
# Master version for Pillow
__version__ = "9.4.0.post1"
__version__ = "9.4.0.post2"
6 changes: 4 additions & 2 deletions src/_imaging.c
Original file line number Diff line number Diff line change
Expand Up @@ -723,6 +723,7 @@ _prepare_lut_table(PyObject *table, Py_ssize_t table_size) {

/* NOTE: This value should be the same as in ColorLUT.c */
#define PRECISION_BITS (16 - 8 - 2)
#define PRECISION_ROUNDING (1 << (PRECISION_BITS - 1))

const char *wrong_size =
("The table should have table_channels * "
Expand Down Expand Up @@ -787,8 +788,8 @@ _prepare_lut_table(PyObject *table, Py_ssize_t table_size) {
break;
}
/* Max value for INT16 */
if (item >= (0x7fff - 0.5) / (255 << PRECISION_BITS)) {
prepared[i] = 0x7fff;
if (item >= (0x7fff - 0.5 - PRECISION_ROUNDING) / (255 << PRECISION_BITS)) {
prepared[i] = 0x7fff - PRECISION_ROUNDING;
continue;
}
/* Min value for INT16 */
Expand All @@ -804,6 +805,7 @@ _prepare_lut_table(PyObject *table, Py_ssize_t table_size) {
}

#undef PRECISION_BITS
#undef PRECISION_ROUNDING
if (free_table_data) {
free(table_data);
}
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8 changes: 4 additions & 4 deletions src/libImaging/ColorLUT.c
Original file line number Diff line number Diff line change
Expand Up @@ -233,7 +233,7 @@ ImagingColorLUT3D_linear(
__m128i source = _mm_loadu_si128((__m128i *) &rowIn[x]);
// scale up to 16 bits, but scale * 255 * 256 up to 31 bits
// bi, gi and ri - 6 bits index
// rs, rs and rs - 9 bits shift
// bs, gs and rs - 9 bits shift
// 00 bi3.bs3 gi3.gs3 ri3.rs3 00 bi2.bs2 gi2.gs2 ri2.rs2
// 00 bi1.bs1 gi1.gs1 ri1.rs1 00 bi0.bs0 gi0.gs0 ri0.rs0
__m256i index = _mm256_mulhi_epu16(scale256,
Expand All @@ -248,7 +248,7 @@ ImagingColorLUT3D_linear(
__m128i next_source = _mm_loadu_si128((__m128i *) &rowIn[x + 4]);
// scale up to 16 bits, but scale * 255 * 256 up to 31 bits
// bi, gi and ri - 6 bits index
// rs, rs and rs - 9 bits shift
// bs, gs and rs - 9 bits shift
// 00 bi3.bs3 gi3.gs3 ri3.rs3 00 bi2.bs2 gi2.gs2 ri2.rs2
// 00 bi1.bs1 gi1.gs1 ri1.rs1 00 bi0.bs0 gi0.gs0 ri0.rs0
__m256i next_index = _mm256_mulhi_epu16(scale256,
Expand Down Expand Up @@ -332,7 +332,7 @@ ImagingColorLUT3D_linear(
__m128i source = _mm_loadl_epi64((__m128i *) &rowIn[x]);
// scale up to 16 bits, but scale * 255 * 256 up to 31 bits
// bi, gi and ri - 6 bits index
// rs, rs and rs - 9 bits shift
// bs, gs and rs - 9 bits shift
// 00 bi1.bs1 gi1.gs1 ri1.rs1 00 bi0.bs0 gi0.gs0 ri0.rs0
__m128i index = _mm_mulhi_epu16(scale,
_mm_unpacklo_epi8(_mm_setzero_si128(), source));
Expand Down Expand Up @@ -402,7 +402,7 @@ ImagingColorLUT3D_linear(
__m128i source = _mm_cvtsi32_si128(rowIn[x]);
// scale up to 16 bits, but scale * 255 * 256 up to 31 bits
// bi, gi and ri - 6 bits index
// rs, rs and rs - 9 bits shift
// bs, gs and rs - 9 bits shift
// 00 00 00 00 00 bi.bs gi.gs ri.rs
__m128i index = _mm_mulhi_epu16(scale,
_mm_unpacklo_epi8(_mm_setzero_si128(), source));
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