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LibImage: Implement (bi)cubic interpolation 

This is kind of slow but yields much nicer results compared to
(bi)linear interpolation. I should probably add gamma correction...
This commit is contained in:
Bananymous 2024-06-15 23:05:10 +03:00
parent 157e05f57c
commit e6549b0fe8
2 changed files with 99 additions and 24 deletions
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118
LibImage/Image.cpp
View File

@ -76,6 +76,37 @@ namespace LibImage
return BAN::Error::from_errno(ENOTSUP);
}
struct FloatingColor
{
double r, g, b, a;
constexpr FloatingColor() {}
constexpr FloatingColor(double r, double g, double b, double a)
: r(r), g(g), b(b), a(a)
{}
constexpr FloatingColor(Image::Color c)
: r(c.r), g(c.g), b(c.b), a(c.a)
{}
constexpr FloatingColor operator*(double value) const
{
return FloatingColor(r * value, g * value, b * value, a * value);
}
constexpr FloatingColor operator+(FloatingColor other) const
{
return FloatingColor(r + other.r, g + other.g, b + other.b, a + other.a);
}
constexpr Image::Color as_color() const
{
return Image::Color {
.r = static_cast<uint8_t>(BAN::Math::clamp<double>(r, 0.0, 255.0)),
.g = static_cast<uint8_t>(BAN::Math::clamp<double>(g, 0.0, 255.0)),
.b = static_cast<uint8_t>(BAN::Math::clamp<double>(b, 0.0, 255.0)),
.a = static_cast<uint8_t>(BAN::Math::clamp<double>(a, 0.0, 255.0)),
};
}
};
BAN::ErrorOr<BAN::UniqPtr<Image>> Image::resize(uint64_t new_width, uint64_t new_height, ResizeAlgorithm algorithm)
{
if (!validate_size(new_width, new_height))
@ -84,26 +115,26 @@ namespace LibImage
const double ratio_x = (double)width() / new_width;
const double ratio_y = (double)height() / new_height;
const auto get_clamped_color =
[this](int64_t x, int64_t y)
{
x = BAN::Math::clamp<int64_t>(x, 0, width() - 1);
y = BAN::Math::clamp<int64_t>(y, 0, height() - 1);
return get_color(x, y);
};
switch (algorithm)
{
case ResizeAlgorithm::Nearest:
{
BAN::Vector<Color> nearest_bitmap;
TRY(nearest_bitmap.resize(new_width * new_height));
for (uint64_t y = 0; y < new_height; y++)
{
for (uint64_t x = 0; x < new_width; x++)
{
const uint64_t nearest_x = BAN::Math::clamp<uint64_t>(x * ratio_x, 0, width() - 1);
const uint64_t nearest_y = BAN::Math::clamp<uint64_t>(y * ratio_y, 0, height() - 1);
nearest_bitmap[y * new_width + x] = get_color(nearest_x, nearest_y);
}
}
nearest_bitmap[y * new_width + x] = get_clamped_color(x * ratio_x, y * ratio_y);
return TRY(BAN::UniqPtr<Image>::create(new_width, new_height, BAN::move(nearest_bitmap)));
}
case ResizeAlgorithm::Bilinear:
case ResizeAlgorithm::Linear:
{
BAN::Vector<Color> bilinear_bitmap;
TRY(bilinear_bitmap.resize(new_width * new_height));
@ -112,25 +143,68 @@ namespace LibImage
{
for (uint64_t x = 0; x < new_width; x++)
{
const double src_x_float = x * ratio_x;
const double src_y_float = y * ratio_y;
const double weight_x = src_x_float - floor(src_x_float);
const double weight_y = src_y_float - floor(src_y_float);
const double src_x = x * ratio_x;
const double src_y = y * ratio_y;
const double weight_x = src_x - floor(src_x);
const double weight_y = src_y - floor(src_y);
const uint64_t src_l = BAN::Math::clamp<uint64_t>(src_x_float, 0, width() - 1);
const uint64_t src_t = BAN::Math::clamp<uint64_t>(src_y_float, 0, height() - 1);
const uint64_t src_r = BAN::Math::clamp<uint64_t>(src_l + 1, 0, width() - 1);
const uint64_t src_b = BAN::Math::clamp<uint64_t>(src_t + 1, 0, height() - 1);
const Color avg_t = Color::average(get_color(src_l, src_t), get_color(src_r, src_t), weight_x);
const Color avg_b = Color::average(get_color(src_l, src_b), get_color(src_r, src_b), weight_x);
const Color avg_t = Color::average(
get_clamped_color(src_x + 0.0, src_y),
get_clamped_color(src_x + 1.0, src_y),
weight_x
);
const Color avg_b = Color::average(
get_clamped_color(src_x + 0.0, src_y + 1.0),
get_clamped_color(src_x + 0.0, src_y + 1.0),
weight_x
);
bilinear_bitmap[y * new_width + x] = Color::average(avg_t, avg_b, weight_y);
}
}
return TRY(BAN::UniqPtr<Image>::create(new_width, new_height, BAN::move(bilinear_bitmap)));
}
case ResizeAlgorithm::Cubic:
{
BAN::Vector<Color> bicubic_bitmap;
TRY(bicubic_bitmap.resize(new_width * new_height));
constexpr auto cubic_interpolate =
[](FloatingColor p[4], double x)
{
const auto a = (p[0] * -0.5) + (p[1] * 1.5) + (p[2] * -1.5) + (p[3] * 0.5);
const auto b = p[0] + (p[1] * -2.5) + (p[2] * 2.0) + (p[3] * -0.5);
const auto c = (p[0] * -0.5) + (p[2] * 0.5);
const auto d = p[1];
return (a * x * x * x) + (b * x * x) + (c * x) + d;
};
for (uint64_t y = 0; y < new_height; y++)
{
for (uint64_t x = 0; x < new_width; x++)
{
const double src_x = x * ratio_x;
const double src_y = y * ratio_y;
const double weight_x = src_x - floor(src_x);
const double weight_y = src_y - floor(src_y);
FloatingColor values[4];
for (int64_t m = -1; m <= 2; m++)
{
FloatingColor p[4];
p[0] = get_clamped_color(src_x - 1.0, src_y + m);
p[1] = get_clamped_color(src_x + 0.0, src_y + m);
p[2] = get_clamped_color(src_x + 1.0, src_y + m);
p[3] = get_clamped_color(src_x + 2.0, src_y + m);
values[m + 1] = cubic_interpolate(p, weight_x);
}
bicubic_bitmap[y * new_width + x] = cubic_interpolate(values, weight_y).as_color();
}
}
return TRY(BAN::UniqPtr<Image>::create(new_width, new_height, BAN::move(bicubic_bitmap)));
}
}
return BAN::Error::from_errno(EINVAL);

5
LibImage/include/LibImage/Image.h
View File

@ -36,13 +36,14 @@ namespace LibImage
enum class ResizeAlgorithm
{
Nearest,
Bilinear,
Linear,
Cubic,
};
public:
static BAN::ErrorOr<BAN::UniqPtr<Image>> load_from_file(BAN::StringView path);
BAN::ErrorOr<BAN::UniqPtr<Image>> resize(uint64_t new_width, uint64_t new_height, ResizeAlgorithm = ResizeAlgorithm::Bilinear);
BAN::ErrorOr<BAN::UniqPtr<Image>> resize(uint64_t new_width, uint64_t new_height, ResizeAlgorithm = ResizeAlgorithm::Cubic);
Color get_color(uint64_t x, uint64_t y) const { return m_bitmap[y * width() + x]; }
const BAN::Vector<Color> bitmap() const { return m_bitmap; }