mirror of
https://github.com/xiaoqidun/ofdgo.git
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59 lines
2.4 KiB
Go
59 lines
2.4 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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"image"
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"image/color"
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"golang.org/x/image/draw"
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"golang.org/x/image/math/f64"
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)
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// drawRasterImage 按页面变换采样图像，两后端共享相同的高质量图像插值
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// 入参: dst 目标图像, src 源图像, m 像素坐标变换
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func drawRasterImage(dst draw.Image, src image.Image, m RasterMatrix) {
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draw.CatmullRom.Transform(dst, f64.Aff3{m[0], m[2], m[4], m[1], m[3], m[5]}, src, src.Bounds(), draw.Over, nil)
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}
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// drawRasterImageCommand 使用当前后端生成裁剪蒙版，共用高质量图像采样
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// 入参: backend 当前后端, page 页面, dst 目标图像, src 原始图像, command 图像指令
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// 返回: error 裁剪绘制错误
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func drawRasterImageCommand(backend RasterBackend, page *RasterPage, dst draw.Image, src image.Image, command RasterCommand) error {
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m := page.PixelTransform(command.Transform, dst.Bounds().Dy())
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if command.Clip == nil {
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drawRasterImage(dst, src, m)
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return nil
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}
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mask, err := backend.Render(&RasterPage{Width: page.Width, Height: page.Height, DPI: page.DPI, Commands: []RasterCommand{{Path: command.Clip, Paint: RasterPaint{Color: color.RGBA{255, 255, 255, 255}}, Transform: RasterMatrix{1, 0, 0, 1, 0, 0}}}})
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if err != nil {
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return err
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}
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draw.CatmullRom.Transform(dst, f64.Aff3{m[0], m[2], m[4], m[1], m[3], m[5]}, imagePixelSource(src), src.Bounds(), draw.Over, &draw.Options{DstMask: mask})
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return nil
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}
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// PixelTransform 将页面毫米变换转换为像素变换，保留尺寸取整后的原点位置
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// 入参: m 局部到页面变换, height 目标像素高度
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// 返回: RasterMatrix 局部到像素变换
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func (p *RasterPage) PixelTransform(m RasterMatrix, height int) RasterMatrix {
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scale := p.DPI / 25.4
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for i := range m {
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m[i] *= scale
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}
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m[5] += float64(height) - p.Height*scale
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return m
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}
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