blob: 8bdfbe2cb250788d1fde1fa6903b19b741cc8254 [file] [log] [blame]
// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <algorithm>
#include "flutter/fml/logging.h"
#include "impeller/geometry/gradient.h"
namespace impeller {
static void AppendColor(const Color& color, GradientData* data) {
auto converted = color.ToR8G8B8A8();
data->color_bytes.push_back(converted[0]);
data->color_bytes.push_back(converted[1]);
data->color_bytes.push_back(converted[2]);
data->color_bytes.push_back(converted[3]);
}
GradientData CreateGradientBuffer(const std::vector<Color>& colors,
const std::vector<Scalar>& stops) {
FML_DCHECK(stops.size() == colors.size());
uint32_t texture_size;
if (stops.size() == 2) {
texture_size = colors.size();
} else {
auto minimum_delta = 1.0;
for (size_t i = 1; i < stops.size(); i++) {
auto value = stops[i] - stops[i - 1];
// Smaller than kEhCloseEnough
if (value < 0.0001) {
continue;
}
if (value < minimum_delta) {
minimum_delta = value;
}
}
// Avoid creating textures that are absurdly large due to stops that are
// very close together.
// TODO(jonahwilliams): this should use a platform specific max texture
// size.
texture_size = std::min(
static_cast<uint32_t>(std::round(1.0 / minimum_delta)) + 1, 1024u);
}
GradientData data = {
.color_bytes = {},
.texture_size = texture_size,
};
data.color_bytes.reserve(texture_size * 4);
if (texture_size == colors.size() && colors.size() <= 1024) {
for (auto i = 0u; i < colors.size(); i++) {
AppendColor(colors[i], &data);
}
} else {
Color previous_color = colors[0];
auto previous_stop = 0.0;
auto previous_color_index = 0;
// The first index is always equal to the first color, exactly.
AppendColor(previous_color, &data);
for (auto i = 1u; i < texture_size - 1; i++) {
auto scaled_i = i / (texture_size - 1.0);
Color next_color = colors[previous_color_index + 1];
auto next_stop = stops[previous_color_index + 1];
// We're almost exactly equal to the next stop.
if (ScalarNearlyEqual(scaled_i, next_stop)) {
AppendColor(next_color, &data);
previous_color = next_color;
previous_stop = next_stop;
previous_color_index += 1;
} else if (scaled_i < next_stop) {
// We're still between the current stop and the next stop.
auto t = (scaled_i - previous_stop) / (next_stop - previous_stop);
auto mixed_color = Color::Lerp(previous_color, next_color, t);
AppendColor(mixed_color, &data);
} else {
// We've slightly overshot the previous stop.
previous_color = next_color;
previous_stop = next_stop;
previous_color_index += 1;
next_color = colors[previous_color_index + 1];
auto next_stop = stops[previous_color_index + 1];
auto t = (scaled_i - previous_stop) / (next_stop - previous_stop);
auto mixed_color = Color::Lerp(previous_color, next_color, t);
AppendColor(mixed_color, &data);
}
}
// The last index is always equal to the last color, exactly.
AppendColor(colors.back(), &data);
}
return data;
}
} // namespace impeller