mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 08:46:55 +08:00
133 lines
4.1 KiB
Go
133 lines
4.1 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 "image"
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// pdfCompositeTileSize 限定单次合成块的像素边长
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const pdfCompositeTileSize = 256
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// pdfCompositeBuffers 在一次局部合成中保留至多八个块容量内的空闲缓冲
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type pdfCompositeBuffers[T any] [8][]T
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// pdfCompositeScratch 复用像素及蒙版缓冲，不跨页持有活动内容
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type pdfCompositeScratch struct {
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pixels pdfCompositeBuffers[pdfCompositePixel]
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masks pdfCompositeBuffers[float64]
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rasters [8]*image.RGBA
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}
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// acquireCoverage 借用当前块的独占画布，保留活动画布供嵌套合成读取
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// 返回: *image.RGBA 未清空画布，不支持缓冲绘制的后端返回nil, error 无效绘制区域
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func (c *pdfCompositor) acquireCoverage() (*image.RGBA, error) {
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if _, ok := c.importer.editor.Backends().Raster.(RasterBufferBackend); !ok {
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return nil, nil
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}
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page := RasterPage{Width: c.box.W, Height: c.box.H, DPI: c.importer.rasterDPI}
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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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if c.scratch == nil {
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c.scratch = &pdfCompositeScratch{}
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}
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rect := image.Rect(0, 0, w, h)
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for i, stored := range c.scratch.rasters {
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if stored != nil && stored.Rect == rect {
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c.scratch.rasters[i] = nil
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return stored, nil
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}
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}
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return image.NewRGBA(rect), nil
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}
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// releaseCoverage 归还当前调用不再读取的画布，限制单次合成保留的内存
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// 入参: coverage 当前调用的覆盖图像
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func (c *pdfCompositor) releaseCoverage(coverage image.Image) {
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if _, ok := c.importer.editor.Backends().Raster.(RasterBufferBackend); !ok || c.scratch == nil {
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return
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}
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buffer, ok := coverage.(*image.RGBA)
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if !ok || buffer == nil || cap(buffer.Pix) > 4*pdfCompositeTileSize*pdfCompositeTileSize {
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return
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}
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for i, stored := range c.scratch.rasters {
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if stored == nil {
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c.scratch.rasters[i] = buffer
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return
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}
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}
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}
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// acquire 借用尚未初始化的独立缓冲，嵌套调用不复用活动缓冲
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// 入参: count 所需元素数量
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// 返回: []T 可由当前调用独占的缓冲
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func (s *pdfCompositeBuffers[T]) acquire(count int) []T {
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selected := -1
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for i, buffer := range s {
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if cap(buffer) >= count && (selected < 0 || cap(buffer) < cap(s[selected])) {
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selected = i
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}
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}
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if selected < 0 {
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return make([]T, count)
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}
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buffer := s[selected]
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s[selected] = nil
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return buffer[:count]
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}
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// release 归还已不再访问的缓冲，超出块容量或空闲槽数量时直接释放
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// 入参: buffer 当前调用借用的缓冲
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func (s *pdfCompositeBuffers[T]) release(buffer []T) {
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if len(buffer) == 0 || cap(buffer) > pdfCompositeTileSize*pdfCompositeTileSize {
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return
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}
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for i, stored := range s {
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if stored == nil {
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s[i] = buffer
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return
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}
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}
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}
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// acquirePixels 为当前合成器借用独立像素缓冲
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// 入参: count 所需像素数量
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// 返回: []pdfCompositePixel 尚未初始化的独占缓冲
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func (c *pdfCompositor) acquirePixels(count int) []pdfCompositePixel {
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if c.scratch == nil {
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c.scratch = &pdfCompositeScratch{}
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}
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return c.scratch.pixels.acquire(count)
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}
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// releasePixels 归还当前调用已不再访问的像素缓冲
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// 入参: pixels 当前调用借用的缓冲
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func (c *pdfCompositor) releasePixels(pixels []pdfCompositePixel) {
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if c.scratch != nil {
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c.scratch.pixels.release(pixels)
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}
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}
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// releaseMasks 在当前块绘制结束后归还蒙版结果，不复用其他块的坐标缓存
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func (c *pdfCompositor) releaseMasks() {
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if c.scratch != nil {
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for _, mask := range c.masks {
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c.scratch.masks.release(mask)
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}
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}
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clear(c.masks)
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}
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