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https://github.com/RGBCube/serenity
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b31d768e95
Also while here add option to disable pre-multiplied alpha for gradients (this will be handy later).
282 lines
12 KiB
C++
282 lines
12 KiB
C++
/*
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* Copyright (c) 2022-2023, MacDue <macdue@dueutil.tech>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Math.h>
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#include <LibGfx/Gradients.h>
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#include <LibGfx/PaintStyle.h>
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#include <LibGfx/Painter.h>
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#if defined(AK_COMPILER_GCC)
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# pragma GCC optimize("O3")
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#endif
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namespace Gfx {
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// Note: This file implements the CSS gradients for LibWeb according to the spec.
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// Please do not make ad-hoc changes that may break spec compliance!
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static float color_stop_step(ColorStop const& previous_stop, ColorStop const& next_stop, float position)
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{
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if (position < previous_stop.position)
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return 0;
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if (position > next_stop.position)
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return 1;
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// For any given point between the two color stops,
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// determine the point’s location as a percentage of the distance between the two color stops.
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// Let this percentage be P.
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auto stop_length = next_stop.position - previous_stop.position;
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// FIXME: Avoids NaNs... Still not quite correct?
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if (stop_length <= 0)
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return 1;
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auto p = (position - previous_stop.position) / stop_length;
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if (!next_stop.transition_hint.has_value())
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return p;
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if (*next_stop.transition_hint >= 1)
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return 0;
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if (*next_stop.transition_hint <= 0)
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return 1;
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// Let C, the color weighting at that point, be equal to P^(logH(.5)).
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auto c = AK::pow(p, AK::log<float>(0.5) / AK::log(*next_stop.transition_hint));
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// The color at that point is then a linear blend between the colors of the two color stops,
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// blending (1 - C) of the first stop and C of the second stop.
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return c;
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}
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enum class UsePremultipliedAlpha {
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Yes,
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No
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};
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class GradientLine {
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public:
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GradientLine(int gradient_length, Span<ColorStop const> color_stops, Optional<float> repeat_length, UsePremultipliedAlpha use_premultiplied_alpha = UsePremultipliedAlpha::Yes)
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: m_repeating { repeat_length.has_value() }
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, m_start_offset { round_to<int>((m_repeating ? color_stops.first().position : 0.0f) * gradient_length) }
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{
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// Avoid generating excessive amounts of colors when the not enough shades to fill that length.
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auto necessary_length = min<int>((color_stops.size() - 1) * 255, gradient_length);
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m_sample_scale = float(necessary_length) / gradient_length;
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// Note: color_count will be < gradient_length for repeating gradients.
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auto color_count = round_to<int>(repeat_length.value_or(1.0f) * necessary_length);
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m_gradient_line_colors.resize(color_count);
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auto color_blend = [&](Color a, Color b, float amount) {
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// Note: color.mixed_with() performs premultiplied alpha mixing when necessary as defined in:
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// https://drafts.csswg.org/css-images/#coloring-gradient-line
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if (use_premultiplied_alpha == UsePremultipliedAlpha::Yes)
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return a.mixed_with(b, amount);
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return a.interpolate(b, amount);
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};
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for (int loc = 0; loc < color_count; loc++) {
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auto relative_loc = float(loc + m_start_offset) / necessary_length;
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Color gradient_color = color_blend(color_stops[0].color, color_stops[1].color,
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color_stop_step(color_stops[0], color_stops[1], relative_loc));
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for (size_t i = 1; i < color_stops.size() - 1; i++) {
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gradient_color = color_blend(gradient_color, color_stops[i + 1].color,
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color_stop_step(color_stops[i], color_stops[i + 1], relative_loc));
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}
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m_gradient_line_colors[loc] = gradient_color;
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if (gradient_color.alpha() < 255)
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m_requires_blending = true;
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}
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}
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Color get_color(i64 index) const
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{
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return m_gradient_line_colors[clamp(index, 0, m_gradient_line_colors.size() - 1)];
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}
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Color sample_color(float loc) const
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{
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if (m_sample_scale != 1.0f)
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loc *= m_sample_scale;
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auto repeat_wrap_if_required = [&](i64 loc) {
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if (m_repeating)
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return (loc + m_start_offset) % static_cast<i64>(m_gradient_line_colors.size());
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return loc;
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};
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auto int_loc = static_cast<i64>(floor(loc));
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auto blend = loc - int_loc;
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auto color = get_color(repeat_wrap_if_required(int_loc));
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// Blend between the two neighbouring colors (this fixes some nasty aliasing issues at small angles)
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if (blend >= 0.004f)
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color = color.mixed_with(get_color(repeat_wrap_if_required(int_loc + 1)), blend);
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return color;
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}
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void paint_into_physical_rect(Painter& painter, IntRect rect, auto location_transform)
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{
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auto clipped_rect = rect.intersected(painter.clip_rect() * painter.scale());
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auto start_offset = clipped_rect.location() - rect.location();
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for (int y = 0; y < clipped_rect.height(); y++) {
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for (int x = 0; x < clipped_rect.width(); x++) {
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auto pixel = sample_color(location_transform(x + start_offset.x(), y + start_offset.y()));
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painter.set_physical_pixel(clipped_rect.location().translated(x, y), pixel, m_requires_blending);
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}
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}
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}
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private:
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bool m_repeating;
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int m_start_offset;
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float m_sample_scale { 1 };
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Vector<Color, 1024> m_gradient_line_colors;
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bool m_requires_blending = false;
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};
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template<typename TransformFunction>
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struct Gradient {
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Gradient(GradientLine gradient_line, TransformFunction transform_function)
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: m_gradient_line(move(gradient_line))
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, m_transform_function(move(transform_function))
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{
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}
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void paint(Painter& painter, IntRect rect)
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{
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m_gradient_line.paint_into_physical_rect(painter, rect, m_transform_function);
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}
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PaintStyle::SamplerFunction sample_function()
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{
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return [this](IntPoint point) {
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return m_gradient_line.sample_color(m_transform_function(point.x(), point.y()));
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};
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}
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private:
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GradientLine m_gradient_line;
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TransformFunction m_transform_function;
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};
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static auto create_linear_gradient(IntRect const& physical_rect, Span<ColorStop const> const& color_stops, float angle, Optional<float> repeat_length)
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{
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float normalized_angle = normalized_gradient_angle_radians(angle);
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float sin_angle, cos_angle;
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AK::sincos(normalized_angle, sin_angle, cos_angle);
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// Full length of the gradient
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auto gradient_length = calculate_gradient_length(physical_rect.size(), sin_angle, cos_angle);
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IntPoint offset { cos_angle * (gradient_length / 2), sin_angle * (gradient_length / 2) };
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auto center = physical_rect.translated(-physical_rect.location()).center();
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auto start_point = center - offset;
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// Rotate gradient line to be horizontal
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auto rotated_start_point_x = start_point.x() * cos_angle - start_point.y() * -sin_angle;
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GradientLine gradient_line(gradient_length, color_stops, repeat_length);
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return Gradient {
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move(gradient_line),
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[=](int x, int y) {
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return (x * cos_angle - (physical_rect.height() - y) * -sin_angle) - rotated_start_point_x;
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}
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};
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}
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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)
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{
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// FIXME: Do we need/want sub-degree accuracy for the gradient line?
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GradientLine gradient_line(360, color_stops, repeat_length, use_premultiplied_alpha);
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float normalized_start_angle = (360.0f - start_angle) + 90.0f;
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// The flooring can make gradients that want soft edges look worse, so only floor if we have hard edges.
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// Which makes sure the hard edge stay hard edges :^)
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bool should_floor_angles = false;
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for (size_t i = 0; i < color_stops.size() - 1; i++) {
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if (color_stops[i + 1].position - color_stops[i].position <= 0.01f) {
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should_floor_angles = true;
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break;
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}
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}
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return Gradient {
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move(gradient_line),
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[=](int x, int y) {
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auto point = FloatPoint { x, y } - center_point;
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// FIXME: We could probably get away with some approximation here:
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auto loc = fmod((AK::atan2(point.y(), point.x()) * 180.0f / AK::Pi<float> + 360.0f + normalized_start_angle), 360.0f);
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return should_floor_angles ? floor(loc) : loc;
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}
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};
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}
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static auto create_radial_gradient(IntRect const& physical_rect, Span<ColorStop const> const& color_stops, IntPoint center, IntSize size, Optional<float> repeat_length)
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{
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// A conservative guesstimate on how many colors we need to generate:
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auto max_dimension = max(physical_rect.width(), physical_rect.height());
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auto max_visible_gradient = max(max_dimension / 2, min(size.width(), max_dimension));
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GradientLine gradient_line(max_visible_gradient, color_stops, repeat_length);
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auto center_point = FloatPoint { center }.translated(0.5, 0.5);
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return Gradient {
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move(gradient_line),
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[=](int x, int y) {
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// FIXME: See if there's a more efficient calculation we do there :^)
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auto point = FloatPoint(x, y) - center_point;
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auto gradient_x = point.x() / size.width();
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auto gradient_y = point.y() / size.height();
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return AK::sqrt(gradient_x * gradient_x + gradient_y * gradient_y) * max_visible_gradient;
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}
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};
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}
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void Painter::fill_rect_with_linear_gradient(IntRect const& rect, Span<ColorStop const> const& color_stops, float angle, Optional<float> repeat_length)
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{
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auto a_rect = to_physical(rect);
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if (a_rect.intersected(clip_rect() * scale()).is_empty())
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return;
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auto linear_gradient = create_linear_gradient(a_rect, color_stops, angle, repeat_length);
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linear_gradient.paint(*this, a_rect);
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}
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static FloatPoint pixel_center(IntPoint point)
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{
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return point.to_type<float>().translated(0.5f, 0.5f);
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}
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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)
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{
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auto a_rect = to_physical(rect);
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if (a_rect.intersected(clip_rect() * scale()).is_empty())
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return;
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// Translate position/center to the center of the pixel (avoids some funky painting)
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auto center_point = pixel_center(center * scale());
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auto conic_gradient = create_conic_gradient(color_stops, center_point, start_angle, repeat_length);
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conic_gradient.paint(*this, a_rect);
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}
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void Painter::fill_rect_with_radial_gradient(IntRect const& rect, Span<ColorStop const> const& color_stops, IntPoint center, IntSize size, Optional<float> repeat_length)
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{
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auto a_rect = to_physical(rect);
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if (a_rect.intersected(clip_rect() * scale()).is_empty())
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return;
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auto radial_gradient = create_radial_gradient(a_rect, color_stops, center * scale(), size * scale(), repeat_length);
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radial_gradient.paint(*this, a_rect);
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}
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// TODO: Figure out how to handle scale() here... Not important while not supported by fill_path()
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void LinearGradientPaintStyle::paint(IntRect physical_bounding_box, PaintFunction paint) const
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{
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VERIFY(color_stops().size() > 2);
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auto linear_gradient = create_linear_gradient(physical_bounding_box, color_stops(), m_angle, repeat_length());
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paint(linear_gradient.sample_function());
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}
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void ConicGradientPaintStyle::paint(IntRect physical_bounding_box, PaintFunction paint) const
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{
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VERIFY(color_stops().size() > 2);
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(void)physical_bounding_box;
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auto conic_gradient = create_conic_gradient(color_stops(), pixel_center(m_center), m_start_angle, repeat_length());
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paint(conic_gradient.sample_function());
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}
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void RadialGradientPaintStyle::paint(IntRect physical_bounding_box, PaintFunction paint) const
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{
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VERIFY(color_stops().size() > 2);
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auto radial_gradient = create_radial_gradient(physical_bounding_box, color_stops(), m_center, m_size, repeat_length());
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paint(radial_gradient.sample_function());
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}
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}
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