mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 16:44:23 +08:00
112 lines
3.6 KiB
Go
112 lines
3.6 KiB
Go
// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ofdgo
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import "math"
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// reflectShdPosition 获取镜像周期内的位置
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// 入参: position 渐变位置
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// 返回: float64 周期内的位置
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func reflectShdPosition(position float64) float64 {
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index := math.Floor(position)
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position -= index
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if math.Mod(index, 2) != 0 {
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return 1 - position
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}
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return position
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}
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// shadingClip 按渐变延伸规则裁剪绘制与选区，避免只在采样时隐藏区间外像素
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// 入参: path 页面路径, paint 渐变画刷, matrix 渐变父矩阵
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// 返回: GeometryPath 可见路径, error 几何错误
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func (c *semanticCompiler) shadingClip(path GeometryPath, paint Paint, matrix Matrix) (GeometryPath, error) {
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gradient, view := semanticGradient(paint, matrix)
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spread := gradient.Spread
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if gradient.Kind == RasterRadial && math.Hypot(gradient.End.X-gradient.Start.X, gradient.End.Y-gradient.Start.Y) >= math.Abs(gradient.R1-gradient.R0) {
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return path, nil
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}
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if spread == nil || spread.Extend == 3 {
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return path, nil
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}
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inverse, ok := view.Invert()
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if !ok {
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return nil, nil
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}
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local, err := c.geometry.Transform(path, inverse)
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if err != nil {
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return nil, err
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}
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if gradient.Kind == RasterLinear {
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dx, dy := gradient.End.X-gradient.Start.X, gradient.End.Y-gradient.Start.Y
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axis := Matrix{a: dx, b: dy, c: -dy, d: dx, e: gradient.Start.X, f: gradient.Start.Y}
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inv, _ := axis.Invert()
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box, err := c.geometry.Bounds(local)
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if err != nil {
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return nil, err
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}
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box = inv.TransformBox(box)
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end := box.X + box.W
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if spread.Extend&1 == 0 {
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box.X = math.Max(box.X, 0)
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}
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if spread.Extend&2 == 0 {
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end = math.Min(end, 1)
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}
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box.W = end - box.X
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if box.W <= 0 {
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return nil, nil
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}
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clip, err := c.geometry.Transform(geometryRectangle(box), axis)
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if err != nil {
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return nil, err
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}
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local, err = c.geometry.Combine(local, clip, GeometryIntersect)
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if err != nil {
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return nil, err
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}
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} else {
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inner, outer, r0, r1, extend := gradient.Start, gradient.End, gradient.R0, gradient.R1, spread.Extend
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if r1 < r0 {
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inner, outer, r0, r1 = outer, inner, r1, r0
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extend = (extend&1)<<1 | (extend&2)>>1
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}
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if extend&2 == 0 {
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local, err = c.geometry.Combine(local, geometryCircle(outer, r1), GeometryIntersect)
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if err != nil {
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return nil, err
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}
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}
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if extend&1 == 0 && r0 > 0 {
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local, err = c.geometry.Combine(local, geometryCircle(inner, r0), GeometrySubtract)
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if err != nil {
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return nil, err
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}
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}
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}
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return c.geometry.Transform(local, view)
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}
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// geometryCircle 构建标准圆弧，不提前折线化
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// 入参: center 圆心, radius 半径
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// 返回: GeometryPath 圆路径
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func geometryCircle(center RasterPoint, radius float64) GeometryPath {
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return GeometryPath{
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{Verb: GeometryMove, End: Point{X: center.X + radius, Y: center.Y}},
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{Verb: GeometryArc, RadiusX: radius, RadiusY: radius, Sweep: true, End: Point{X: center.X - radius, Y: center.Y}},
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{Verb: GeometryArc, RadiusX: radius, RadiusY: radius, Sweep: true, End: Point{X: center.X + radius, Y: center.Y}},
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{Verb: GeometryClose},
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}
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}
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