mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 15:06:46 +08:00
114 lines
3.8 KiB
Go
114 lines
3.8 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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"crypto/sha256"
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"encoding/binary"
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"fmt"
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"image"
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"image/color"
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"math"
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)
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// rasterClipKey 区分页面尺寸、分辨率和裁剪路径
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// 入参: page 页面, path 页面坐标路径
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// 返回: [32]byte 缓存键
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func rasterClipKey(page *RasterPage, path []RasterSegment) [32]byte {
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hash := sha256.New()
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var data [8]byte
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number := func(v float64) {
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binary.LittleEndian.PutUint64(data[:], math.Float64bits(v))
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hash.Write(data[:])
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}
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number(page.Width)
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number(page.Height)
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number(page.DPI)
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for _, s := range path {
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hash.Write([]byte{byte(s.Verb)})
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for _, p := range []RasterPoint{s.End, s.Control1, s.Control2} {
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number(p.X)
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number(p.Y)
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}
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}
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var key [32]byte
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copy(key[:], hash.Sum(nil))
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return key
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}
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// rasterClipMask 使用所选后端生成区域化透明度蒙版，同页相同裁剪可复用
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// 入参: backend 光栅后端, page 页面, path 页面坐标裁剪, cache 蒙版缓存
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// 返回: *image.Alpha 页面像素坐标蒙版, error 绘制错误
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func rasterClipMask(backend RasterBackend, page *RasterPage, path []RasterSegment, cache *renderCache[[32]byte, *image.Alpha]) (*image.Alpha, error) {
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key := rasterClipKey(page, path)
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if mask, ok := cache.get(key); ok {
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return mask, nil
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}
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w, h, err := page.PixelSize()
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if err != nil {
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return nil, err
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}
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matrix := page.PixelTransform(RasterMatrix{1, 0, 0, 1, 0, 0}, h)
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minX, minY, maxX, maxY := math.Inf(1), math.Inf(1), math.Inf(-1), math.Inf(-1)
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include := func(p RasterPoint) {
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p = matrix.Apply(p)
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minX = math.Min(minX, p.X)
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minY = math.Min(minY, p.Y)
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maxX = math.Max(maxX, p.X)
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maxY = math.Max(maxY, p.Y)
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}
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for _, s := range path {
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switch s.Verb {
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case RasterMove, RasterLine:
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include(s.End)
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case RasterQuad:
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include(s.End)
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include(s.Control1)
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case RasterCubic:
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include(s.End)
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include(s.Control1)
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include(s.Control2)
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case RasterClose:
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default:
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return nil, fmt.Errorf("invalid clip path command %d", s.Verb)
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}
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}
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if len(path) == 0 || minX > maxX || minY > maxY {
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return image.NewAlpha(image.Rectangle{}), nil
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}
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if !finite(minX) || !finite(minY) || !finite(maxX) || !finite(maxY) {
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return nil, fmt.Errorf("invalid clip coordinates")
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}
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bounds := image.Rect(int(math.Max(0, math.Min(float64(w), math.Floor(minX)-1))), int(math.Max(0, math.Min(float64(h), math.Floor(minY)-1))), int(math.Max(0, math.Min(float64(w), math.Ceil(maxX)+1))), int(math.Max(0, math.Min(float64(h), math.Ceil(maxY)+1))))
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mask := image.NewAlpha(bounds)
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if !bounds.Empty() {
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scale := page.DPI / 25.4
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local := &RasterPage{Width: float64(bounds.Dx()) / scale, Height: float64(bounds.Dy()) / scale, DPI: page.DPI}
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local.Commands = []RasterCommand{{Path: path, Paint: RasterPaint{Color: color.RGBA{255, 255, 255, 255}}, Transform: RasterMatrix{1, 0, 0, 1, -float64(bounds.Min.X) / scale, (matrix[5] - float64(bounds.Min.Y)) / scale}}}
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pixels, err := backend.Render(local)
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if err != nil {
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return nil, err
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}
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for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
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for x := bounds.Min.X; x < bounds.Max.X; x++ {
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_, _, _, alpha := pixels.At(x-bounds.Min.X, y-bounds.Min.Y).RGBA()
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mask.SetAlpha(x, y, color.Alpha{uint8(alpha >> 8)})
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}
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}
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}
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cache.put(key, mask, len(mask.Pix)+256)
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return mask, nil
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}
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