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LibGfx: Add paint styles and allow gradients to be used as them

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Also while here add option to disable pre-multiplied alpha for gradients
(this will be handy later).
This commit is contained in:
MacDue 2023-01-15 22:10:36 +00:00 • committed by Andreas Kling
parent 19ce63babf
commit b31d768e95
3 changed files with 284 additions and 43 deletions
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176
Userland/Libraries/LibGfx/GradientPainting.cpp
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@ -6,11 +6,13 @@
#include <AK/Math.h>
#include <LibGfx/Gradients.h>
#include <LibGfx/PaintStyle.h>
#include <LibGfx/Painter.h>
#if defined(AK_COMPILER_GCC)
# pragma GCC optimize("O3")
#endif
namespace Gfx {
// Note: This file implements the CSS gradients for LibWeb according to the spec.
@ -43,9 +45,14 @@ static float color_stop_step(ColorStop const& previous_stop, ColorStop const& ne
return c;
}
enum class UsePremultipliedAlpha {
Yes,
No
};
class GradientLine {
public:
GradientLine(int gradient_length, Span<ColorStop const> color_stops, Optional<float> repeat_length)
GradientLine(int gradient_length, Span<ColorStop const> color_stops, Optional<float> repeat_length, UsePremultipliedAlpha use_premultiplied_alpha = UsePremultipliedAlpha::Yes)
: m_repeating { repeat_length.has_value() }
, m_start_offset { round_to<int>((m_repeating ? color_stops.first().position : 0.0f) * gradient_length) }
{
@ -55,16 +62,21 @@ public:
// Note: color_count will be < gradient_length for repeating gradients.
auto color_count = round_to<int>(repeat_length.value_or(1.0f) * necessary_length);
m_gradient_line_colors.resize(color_count);
// Note: color.mixed_with() performs premultiplied alpha mixing when necessary as defined in:
// https://drafts.csswg.org/css-images/#coloring-gradient-line
auto color_blend = [&](Color a, Color b, float amount) {
// Note: color.mixed_with() performs premultiplied alpha mixing when necessary as defined in:
// https://drafts.csswg.org/css-images/#coloring-gradient-line
if (use_premultiplied_alpha == UsePremultipliedAlpha::Yes)
return a.mixed_with(b, amount);
return a.interpolate(b, amount);
};
for (int loc = 0; loc < color_count; loc++) {
auto relative_loc = float(loc + m_start_offset) / necessary_length;
Color gradient_color = color_stops[0].color.mixed_with(
color_stops[1].color,
Color gradient_color = color_blend(color_stops[0].color, color_stops[1].color,
color_stop_step(color_stops[0], color_stops[1], relative_loc));
for (size_t i = 1; i < color_stops.size() - 1; i++) {
gradient_color = gradient_color.mixed_with(
color_stops[i + 1].color,
gradient_color = color_blend(gradient_color, color_stops[i + 1].color,
color_stop_step(color_stops[i], color_stops[i + 1], relative_loc));
}
m_gradient_line_colors[loc] = gradient_color;
@ -117,41 +129,59 @@ private:
bool m_requires_blending = false;
};
void Painter::fill_rect_with_linear_gradient(IntRect const& rect, Span<ColorStop const> const& color_stops, float angle, Optional<float> repeat_length)
{
auto a_rect = to_physical(rect);
if (a_rect.intersected(clip_rect() * scale()).is_empty())
return;
template<typename TransformFunction>
struct Gradient {
Gradient(GradientLine gradient_line, TransformFunction transform_function)
: m_gradient_line(move(gradient_line))
, m_transform_function(move(transform_function))
{
}
void paint(Painter& painter, IntRect rect)
{
m_gradient_line.paint_into_physical_rect(painter, rect, m_transform_function);
}
PaintStyle::SamplerFunction sample_function()
{
return [this](IntPoint point) {
return m_gradient_line.sample_color(m_transform_function(point.x(), point.y()));
};
}
private:
GradientLine m_gradient_line;
TransformFunction m_transform_function;
};
static auto create_linear_gradient(IntRect const& physical_rect, Span<ColorStop const> const& color_stops, float angle, Optional<float> repeat_length)
{
float normalized_angle = normalized_gradient_angle_radians(angle);
float sin_angle, cos_angle;
AK::sincos(normalized_angle, sin_angle, cos_angle);
// Full length of the gradient
auto gradient_length = calculate_gradient_length(a_rect.size(), sin_angle, cos_angle);
auto gradient_length = calculate_gradient_length(physical_rect.size(), sin_angle, cos_angle);
IntPoint offset { cos_angle * (gradient_length / 2), sin_angle * (gradient_length / 2) };
auto center = a_rect.translated(-a_rect.location()).center();
auto center = physical_rect.translated(-physical_rect.location()).center();
auto start_point = center - offset;
// Rotate gradient line to be horizontal
auto rotated_start_point_x = start_point.x() * cos_angle - start_point.y() * -sin_angle;
GradientLine gradient_line(gradient_length, color_stops, repeat_length);
gradient_line.paint_into_physical_rect(*this, a_rect, [&](int x, int y) {
return (x * cos_angle - (a_rect.height() - y) * -sin_angle) - rotated_start_point_x;
});
return Gradient {
move(gradient_line),
[=](int x, int y) {
return (x * cos_angle - (physical_rect.height() - y) * -sin_angle) - rotated_start_point_x;
}
};
}
void Painter::fill_rect_with_conic_gradient(IntRect const& rect, Span<ColorStop const> const& color_stops, IntPoint center, float start_angle, Optional<float> repeat_length)
static auto create_conic_gradient(Span<ColorStop const> const& color_stops, FloatPoint center_point, float start_angle, Optional<float> repeat_length, UsePremultipliedAlpha use_premultiplied_alpha = UsePremultipliedAlpha::Yes)
{
auto a_rect = to_physical(rect);
if (a_rect.intersected(clip_rect() * scale()).is_empty())
return;
// FIXME: Do we need/want sub-degree accuracy for the gradient line?
GradientLine gradient_line(360, color_stops, repeat_length);
GradientLine gradient_line(360, color_stops, repeat_length, use_premultiplied_alpha);
float normalized_start_angle = (360.0f - start_angle) + 90.0f;
// Translate position/center to the center of the pixel (avoids some funky painting)
auto center_point = FloatPoint { center * scale() }.translated(0.5, 0.5);
// The flooring can make gradients that want soft edges look worse, so only floor if we have hard edges.
// Which makes sure the hard edge stay hard edges :^)
bool should_floor_angles = false;
@ -161,12 +191,59 @@ void Painter::fill_rect_with_conic_gradient(IntRect const& rect, Span<ColorStop
break;
}
}
gradient_line.paint_into_physical_rect(*this, a_rect, [&](int x, int y) {
auto point = FloatPoint { x, y } - center_point;
// FIXME: We could probably get away with some approximation here:
auto loc = fmod((AK::atan2(point.y(), point.x()) * 180.0f / AK::Pi<float> + 360.0f + normalized_start_angle), 360.0f);
return should_floor_angles ? floor(loc) : loc;
});
return Gradient {
move(gradient_line),
[=](int x, int y) {
auto point = FloatPoint { x, y } - center_point;
// FIXME: We could probably get away with some approximation here:
auto loc = fmod((AK::atan2(point.y(), point.x()) * 180.0f / AK::Pi<float> + 360.0f + normalized_start_angle), 360.0f);
return should_floor_angles ? floor(loc) : loc;
}
};
}
static auto create_radial_gradient(IntRect const& physical_rect, Span<ColorStop const> const& color_stops, IntPoint center, IntSize size, Optional<float> repeat_length)
{
// A conservative guesstimate on how many colors we need to generate:
auto max_dimension = max(physical_rect.width(), physical_rect.height());
auto max_visible_gradient = max(max_dimension / 2, min(size.width(), max_dimension));
GradientLine gradient_line(max_visible_gradient, color_stops, repeat_length);
auto center_point = FloatPoint { center }.translated(0.5, 0.5);
return Gradient {
move(gradient_line),
[=](int x, int y) {
// FIXME: See if there's a more efficient calculation we do there :^)
auto point = FloatPoint(x, y) - center_point;
auto gradient_x = point.x() / size.width();
auto gradient_y = point.y() / size.height();
return AK::sqrt(gradient_x * gradient_x + gradient_y * gradient_y) * max_visible_gradient;
}
};
}
void Painter::fill_rect_with_linear_gradient(IntRect const& rect, Span<ColorStop const> const& color_stops, float angle, Optional<float> repeat_length)
{
auto a_rect = to_physical(rect);
if (a_rect.intersected(clip_rect() * scale()).is_empty())
return;
auto linear_gradient = create_linear_gradient(a_rect, color_stops, angle, repeat_length);
linear_gradient.paint(*this, a_rect);
}
static FloatPoint pixel_center(IntPoint point)
{
return point.to_type<float>().translated(0.5f, 0.5f);
}
void Painter::fill_rect_with_conic_gradient(IntRect const& rect, Span<ColorStop const> const& color_stops, IntPoint center, float start_angle, Optional<float> repeat_length)
{
auto a_rect = to_physical(rect);
if (a_rect.intersected(clip_rect() * scale()).is_empty())
return;
// Translate position/center to the center of the pixel (avoids some funky painting)
auto center_point = pixel_center(center * scale());
auto conic_gradient = create_conic_gradient(color_stops, center_point, start_angle, repeat_length);
conic_gradient.paint(*this, a_rect);
}
void Painter::fill_rect_with_radial_gradient(IntRect const& rect, Span<ColorStop const> const& color_stops, IntPoint center, IntSize size, Optional<float> repeat_length)
@ -174,19 +251,32 @@ void Painter::fill_rect_with_radial_gradient(IntRect const& rect, Span<ColorStop
auto a_rect = to_physical(rect);
if (a_rect.intersected(clip_rect() * scale()).is_empty())
return;
auto radial_gradient = create_radial_gradient(a_rect, color_stops, center * scale(), size * scale(), repeat_length);
radial_gradient.paint(*this, a_rect);
}
// A conservative guesstimate on how many colors we need to generate:
auto max_dimension = max(a_rect.width(), a_rect.height());
auto max_visible_gradient = max(max_dimension / 2, min(size.width(), max_dimension));
GradientLine gradient_line(max_visible_gradient, color_stops, repeat_length);
auto center_point = FloatPoint { center * scale() }.translated(0.5, 0.5);
gradient_line.paint_into_physical_rect(*this, a_rect, [&](int x, int y) {
// FIXME: See if there's a more efficient calculation we do there :^)
auto point = FloatPoint(x, y) - center_point;
auto gradient_x = point.x() / size.width();
auto gradient_y = point.y() / size.height();
return AK::sqrt(gradient_x * gradient_x + gradient_y * gradient_y) * max_visible_gradient;
});
// TODO: Figure out how to handle scale() here... Not important while not supported by fill_path()
void LinearGradientPaintStyle::paint(IntRect physical_bounding_box, PaintFunction paint) const
{
VERIFY(color_stops().size() > 2);
auto linear_gradient = create_linear_gradient(physical_bounding_box, color_stops(), m_angle, repeat_length());
paint(linear_gradient.sample_function());
}
void ConicGradientPaintStyle::paint(IntRect physical_bounding_box, PaintFunction paint) const
{
VERIFY(color_stops().size() > 2);
(void)physical_bounding_box;
auto conic_gradient = create_conic_gradient(color_stops(), pixel_center(m_center), m_start_angle, repeat_length());
paint(conic_gradient.sample_function());
}
void RadialGradientPaintStyle::paint(IntRect physical_bounding_box, PaintFunction paint) const
{
VERIFY(color_stops().size() > 2);
auto radial_gradient = create_radial_gradient(physical_bounding_box, color_stops(), m_center, m_size, repeat_length());
paint(radial_gradient.sample_function());
}
}