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AK: Make FixedPoint(FloatingPoint) ctor round instead of truncating

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This is needed to have code for creating an in-memory sRGB profile using
the (floating-ppoint) numbers from the sRGB spec and having the
fixed-point values in the profile match what they are in other software
(such as GIMP).

It has the side effect of making the FixedPoint ctor no longer constexpr
(which seems fine; nothing was currently relying on that).

Some of FixedPoint's member functions don't round yet, which requires
tweaking a test.
This commit is contained in:
Nico Weber 2023-03-01 18:34:01 -05:00 committed by Linus Groh
parent 62f2f0a081
commit b898a46d7f
Notes: sideshowbarker 2024-07-16 23:34:26 +09:00 
Author: https://github.com/nico
Commit: https://github.com/SerenityOS/serenity/commit/b898a46d7f
Pull-request: https://github.com/SerenityOS/serenity/pull/17691
Reviewed-by: https://github.com/linusg
3 changed files with 33 additions and 12 deletions
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6
AK/FixedPoint.h
View file

@ -36,11 +36,13 @@ public:
{
}
#ifndef KERNEL
template<FloatingPoint F>
constexpr FixedPoint(F value)
: m_value(static_cast<Underlying>(value * (static_cast<Underlying>(1) << precision)))
FixedPoint(F value)
: m_value(round_to<Underlying>(value * (static_cast<Underlying>(1) << precision)))
{
}
#endif
template<size_t P, typename U>
explicit constexpr FixedPoint(FixedPoint<P, U> const& other)

22
Tests/AK/TestFixedPoint.cpp
View file

@ -72,6 +72,16 @@ TEST_CASE(rounding)
EXPECT_EQ(Type(-1.5).lfloor(), -2);
EXPECT_EQ(Type(-1.5).lceil(), -1);
EXPECT_EQ(Type(-1.5).ltrunk(), -1);
// Check that sRGB TRC curve parameters match the s15fixed16 values stored in Gimp's built-in profile.
// (This only requires that the FixedPoint<> constructor rounds before truncating to the fixed-point value,
// as it should anyways.)
using S15Fixed16 = FixedPoint<16, i32>;
EXPECT_EQ(S15Fixed16(2.4).raw(), 0x26666);
EXPECT_EQ(S15Fixed16(1 / 1.055).raw(), 0xf2a7);
EXPECT_EQ(S15Fixed16(0.055 / 1.055).raw(), 0xd59);
EXPECT_EQ(S15Fixed16(1 / 12.92).raw(), 0x13d0);
EXPECT_EQ(S15Fixed16(0.04045).raw(), 0xa5b);
}
TEST_CASE(logarithm)
@ -115,7 +125,7 @@ TEST_CASE(cast)
{
FixedPoint<16, u32> downcast_value1(FixedPoint<32, u64>(123.4567));
EXPECT((double)downcast_value1 >= 123.4566 && (double)downcast_value1 <= 123.4568);
static constexpr FixedPoint<32, u64> value1(321.7654);
static FixedPoint<32, u64> const value1(321.7654);
downcast_value1 = value1;
EXPECT((double)downcast_value1 >= 321.7653 && (double)downcast_value1 <= 321.7655);
FixedPoint<6, u32> downcast_value2(FixedPoint<32, u64>(4567.123456));
@ -150,12 +160,12 @@ TEST_CASE(formatter)
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<4>(123.456)), "123.4375"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<4>(-123.456)), "-123.4375"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16> {}), "0"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.1)), "0.09999"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.02)), "0.019989"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.003)), "0.00299"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.1)), "0.100006"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.02)), "0.020004"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.003)), "0.003005"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.0004)), "0.000396"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(0.0000000005)), "0"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(-0.1)), "-0.099991"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(-0.02)), "-0.01999"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(-0.1)), "-0.100007"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(-0.02)), "-0.020005"sv);
EXPECT_EQ(DeprecatedString::formatted("{}", FixedPoint<16>(-0.0000000005)), "0"sv);
}

17
Tests/LibEDID/TestEDID.cpp
View file

@ -520,10 +520,19 @@ TEST_CASE(dmt_frequency)
{
auto* dmt = EDID::DMT::find_timing_by_dmt_id(0x4);
EXPECT(dmt);
static constexpr FixedPoint<16, u32> expected_vertical_frequency(59.940);
EXPECT(dmt->vertical_frequency_hz() == expected_vertical_frequency);
static constexpr FixedPoint<16, u32> expected_horizontal_frequency(31.469);
EXPECT(dmt->horizontal_frequency_khz() == expected_horizontal_frequency);
// FIXME: Use the FixedPoint(double) ctor like `expected_vertical_frequency(59.940)` instead of
// dividing by 1000 in the next line once FixedPoint::operator/ rounds.
// 1. DMT.cpp is built as part of the kernel (despite being in Userland/)
// 2. The Kernel can't use floating point
// 3. So it has to use FixedPoint(59940) / 1000
// 4. The FixedPoint(double) ctor rounds, but FixedPoint::operator/ currently doesn't,
// so FixedPoint(59.940) has a different lowest bit than
// FixedPoint(59940) / 1000. So the test can't use the FixedPoint(double) ctor at the moment.
static FixedPoint<16, u32> const expected_vertical_frequency(59940);
EXPECT(dmt->vertical_frequency_hz() == expected_vertical_frequency / 1000);
static FixedPoint<16, u32> const expected_horizontal_frequency(31469);
EXPECT(dmt->horizontal_frequency_khz() == expected_horizontal_frequency / 1000);
}
TEST_CASE(vic)