mirror of
https://github.com/xiaoqidun/ofdgo.git
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102 lines
3.5 KiB
Go
102 lines
3.5 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 (
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"fmt"
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"math"
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"github.com/tdewolff/canvas"
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)
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// InkPoint 手写采样点，X和Y为毫米，Pressure为0到1的压力
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type InkPoint struct {
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X float64 `json:"x"`
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Y float64 `json:"y"`
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Pressure float64 `json:"pressure"`
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}
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// NewInk 将采样点转为标准矢量路径，等宽笔保留中心线，压感笔使用一次填充的连续轮廓
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// 不推测笔压、不修改输入；单点生成圆点，页面外路径由页面边界裁切
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// 入参: points 采样点, width 等宽线宽或压感最大线宽，单位毫米, pressure 是否使用压力
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// 返回: PathObject 黑色笔迹，可修改颜色和透明度后插入页面或注解, error 错误信息
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func NewInk(points []InkPoint, width float64, pressure bool) (PathObject, error) {
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if len(points) == 0 || !finite(width) || width <= 0 {
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return PathObject{}, fmt.Errorf("ink requires points and a positive finite width")
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}
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path := &canvas.Path{}
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stationary := true
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for i, point := range points {
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if !finite(point.X) || !finite(point.Y) || !finite(point.Pressure) || point.Pressure < 0 || point.Pressure > 1 {
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return PathObject{}, fmt.Errorf("invalid ink point %d", i)
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}
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stationary = stationary && point.X == points[0].X && point.Y == points[0].Y
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if !pressure {
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if i == 0 {
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path.MoveTo(point.X, point.Y)
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} else {
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path.LineTo(point.X, point.Y)
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}
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continue
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}
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radius := width * point.Pressure / 2
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if radius > 0 {
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path = path.Append(canvas.Circle(radius).Translate(point.X, point.Y))
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}
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if i == 0 {
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continue
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}
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previous := points[i-1]
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r := width * previous.Pressure / 2
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dx, dy := point.X-previous.X, point.Y-previous.Y
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length := math.Hypot(dx, dy)
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if radius == 0 && r == 0 || length <= math.Abs(radius-r) {
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continue
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}
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x, y := dx/length, dy/length
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a := (r - radius) / length
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b := math.Sqrt(1 - a*a)
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nx, ny, mx, my := a*x-b*y, a*y+b*x, a*x+b*y, a*y-b*x
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segment := &canvas.Path{}
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segment.MoveTo(previous.X+r*mx, previous.Y+r*my)
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segment.LineTo(point.X+radius*mx, point.Y+radius*my)
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segment.LineTo(point.X+radius*nx, point.Y+radius*ny)
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segment.LineTo(previous.X+r*nx, previous.Y+r*ny)
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segment.Close()
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path = path.Append(segment)
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}
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filled := pressure || stationary
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if !pressure && stationary {
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path = canvas.Circle(width/2).Translate(points[0].X, points[0].Y)
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}
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if path.Empty() {
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return PathObject{}, fmt.Errorf("ink has no visible stroke")
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}
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box := path.Bounds()
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padding := width / 2
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boundary := Box{X: box.X0 - padding, Y: box.Y0 - padding, W: math.Max(box.W(), width) + width, H: math.Max(box.H(), width) + width}
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object := editorClipPath(path.Translate(-boundary.X, -boundary.Y))
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object.Boundary = editorBoxString(boundary)
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stroke := !filled
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object.Fill, object.Stroke = &filled, &stroke
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object.Cap, object.Join, object.LineWidth = "Round", "Round", width
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if filled {
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object.FillColor = &FillColor{Value: "0 0 0"}
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} else {
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object.StrokeColor = &StrokeColor{Value: "0 0 0"}
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}
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return object, nil
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}
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