mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 08:46:55 +08:00
128 lines
5.2 KiB
Go
128 lines
5.2 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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"math"
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baseimage "github.com/xiaoqidun/ofdgo/internal/base/image"
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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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// rasterScaleBufferLimit 限制整像素缩放器的浮点中间缓冲，超出时使用逐行采样
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const rasterScaleBufferLimit = 8 << 20
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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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// drawRasterImage 按页面变换对图像执行高质量采样
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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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drawRasterImagePixels(dst, src, m, draw.Over)
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}
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// drawRasterImagePixels 对轴向缩小使用可分离采样，其余变换保留通用路径
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// 入参: dst 目标图像, src 源图像, m 像素变换, op 合成操作
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func drawRasterImagePixels(dst draw.Image, src image.Image, m RasterMatrix, op draw.Op) {
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b := src.Bounds()
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if dr, ok := rasterScaleBounds(b, m); ok {
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if dr.Intersect(dst.Bounds()).Empty() {
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return
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}
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draw.CatmullRom.Scale(dst, dr, src, b, op, nil)
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return
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}
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if drawRasterAxisImage(dst, src, m, op) {
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return
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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]}, src, b, op, nil)
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}
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// rasterScaleBounds 检查变换是否可无几何取整地使用缩放器，并限制其中间缓冲
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// 入参: b 源边界, m 像素变换
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// 返回: image.Rectangle 缩放边界, bool 是否适用
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func rasterScaleBounds(b image.Rectangle, m RasterMatrix) (image.Rectangle, bool) {
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if b.Empty() || m[1] != 0 || m[2] != 0 || m[0] <= 0 || m[0] > 1 || m[3] <= 0 || m[3] > 1 || m[0] == 1 && m[3] == 1 {
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return image.Rectangle{}, false
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}
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x0, y0 := float64(m[0]*float64(b.Min.X))+m[4], float64(m[3]*float64(b.Min.Y))+m[5]
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x1, y1 := float64(m[0]*float64(b.Max.X))+m[4], float64(m[3]*float64(b.Max.Y))+m[5]
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for _, v := range [4]float64{x0, y0, x1, y1} {
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if v != math.Floor(v) || v < math.MinInt32 || v > math.MaxInt32 {
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return image.Rectangle{}, false
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}
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}
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if x1 <= x0 || y1 <= y0 || b.Dx() > math.MaxInt32 || b.Dy() > math.MaxInt32 || (x1-x0)*float64(b.Dy()) > rasterScaleBufferLimit/32 {
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return image.Rectangle{}, false
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}
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return image.Rect(int(x0), int(y0), int(x1), int(y1)), true
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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, cache 蒙版缓存
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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, cache *renderCache[[32]byte, *image.Alpha]) 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 := rasterClipMask(backend, page, command.Clip, cache)
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if err != nil {
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return err
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}
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if mask.Rect.Empty() {
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return nil
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}
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bounds := mask.Rect.Intersect(dst.Bounds()).Intersect(rasterImageBounds(src.Bounds(), m, dst.Bounds()))
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if bounds.Empty() {
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return nil
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}
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layer := image.NewRGBA64(bounds)
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drawRasterImagePixels(layer, baseimage.PixelSource(src), m, draw.Src)
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draw.DrawMask(dst, bounds, layer, bounds.Min, mask, bounds.Min, draw.Over)
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return nil
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}
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// rasterImageBounds 计算采样器可能写入的像素范围，并在整数转换前裁至目标边界
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// 入参: source 原始像素边界, m 像素变换, target 目标边界
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// 返回: image.Rectangle 受影响的目标像素区域
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func rasterImageBounds(source image.Rectangle, m RasterMatrix, target image.Rectangle) image.Rectangle {
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minX, minY, maxX, maxY := math.Inf(1), math.Inf(1), math.Inf(-1), math.Inf(-1)
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for _, p := range [4]image.Point{source.Min, {X: source.Max.X, Y: source.Min.Y}, {X: source.Min.X, Y: source.Max.Y}, source.Max} {
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x := math.Floor(float64(m[0]*float64(p.X)) + float64(m[2]*float64(p.Y)) + m[4])
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y := math.Floor(float64(m[1]*float64(p.X)) + float64(m[3]*float64(p.Y)) + m[5])
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minX, minY = math.Min(minX, x), math.Min(minY, y)
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maxX, maxY = math.Max(maxX, x+1), math.Max(maxY, y+1)
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}
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minX, minY = math.Max(minX, float64(target.Min.X)), math.Max(minY, float64(target.Min.Y))
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maxX, maxY = math.Min(maxX, float64(target.Max.X)), math.Min(maxY, float64(target.Max.Y))
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if minX >= maxX || minY >= maxY {
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return image.Rectangle{}
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}
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return image.Rect(int(minX), int(minY), int(maxX), int(maxY))
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}
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