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57 lines
2.1 KiB
C++
57 lines
2.1 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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namespace Gfx {
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// Note: This file implements the CSS/Canvas 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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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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void SVGGradientPaintStyle::set_gradient_transform(AffineTransform transform)
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{
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// Note: The scaling is removed so enough points on the gradient line are generated.
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// Otherwise, if you scale a tiny path the gradient looks pixelated.
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m_scale = 1.0f;
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if (auto inverse = transform.inverse(); inverse.has_value()) {
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auto transform_scale = transform.scale();
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m_scale = max(transform_scale.x(), transform_scale.y());
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m_inverse_transform = AffineTransform {}.scale(m_scale, m_scale).multiply(*inverse);
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} else {
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m_inverse_transform = OptionalNone {};
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}
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}
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}
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