feat(渲染编辑): 优化渲染编辑完善资源保存

ofdgo_pdf_composite_scratch.go

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+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+// pdfCompositeTileSize 限定单次合成块的像素边长
+const pdfCompositeTileSize = 256
+
+// pdfCompositeBuffers 在一次局部合成中保留至多八个块容量内的空闲缓冲
+type pdfCompositeBuffers[T any] [8][]T
+
+// pdfCompositeScratch 复用像素及蒙版缓冲，不跨页持有活动内容
+type pdfCompositeScratch struct {
+	pixels pdfCompositeBuffers[pdfCompositePixel]
+	masks  pdfCompositeBuffers[float64]
+}
+
+// acquire 借用尚未初始化的独立缓冲，嵌套调用不复用活动缓冲
+// 入参: count 所需元素数量
+// 返回: []T 可由当前调用独占的缓冲
+func (s *pdfCompositeBuffers[T]) acquire(count int) []T {
+	selected := -1
+	for i, buffer := range s {
+		if cap(buffer) >= count && (selected < 0 || cap(buffer) < cap(s[selected])) {
+			selected = i
+		}
+	}
+	if selected < 0 {
+		return make([]T, count)
+	}
+	buffer := s[selected]
+	s[selected] = nil
+	return buffer[:count]
+}
+
+// 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
+// 入参: buffer 当前调用借用的缓冲
+func (s *pdfCompositeBuffers[T]) release(buffer []T) {
+	if len(buffer) == 0 || cap(buffer) > pdfCompositeTileSize*pdfCompositeTileSize {
+		return
+	}
+	for i, stored := range s {
+		if stored == nil {
+			s[i] = buffer
+			return
+		}
+	}
+}
+
+// acquirePixels 为当前合成器借用独立像素缓冲
+// 入参: count 所需像素数量
+// 返回: []pdfCompositePixel 尚未初始化的独占缓冲
+func (c *pdfCompositor) acquirePixels(count int) []pdfCompositePixel {
+	if c.scratch == nil {
+		c.scratch = &pdfCompositeScratch{}
+	}
+	return c.scratch.pixels.acquire(count)
+}
+
+// releasePixels 归还当前调用已不再访问的像素缓冲
+// 入参: pixels 当前调用借用的缓冲
+func (c *pdfCompositor) releasePixels(pixels []pdfCompositePixel) {
+	if c.scratch != nil {
+		c.scratch.pixels.release(pixels)
+	}
+}
+
+// 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
+func (c *pdfCompositor) releaseMasks() {
+	if c.scratch != nil {
+		for _, mask := range c.masks {
+			c.scratch.masks.release(mask)
+		}
+	}
+	clear(c.masks)
+}