mirror of
https://github.com/xiaoqidun/ofdgo.git
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98 lines
3.0 KiB
Go
98 lines
3.0 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 pdf
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import "image"
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// CompositeTileSize 限定单次合成块的像素边长
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const CompositeTileSize = 256
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// CompositeBuffers 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 CompositeBuffers[T any] [8][]T
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// RasterBuffers 保存按像素尺寸复用的独占覆盖画布
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type RasterBuffers [8]*image.RGBA
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// CoverageRow 读取完整范围内的原生覆盖行，其他类型沿用逐点采样
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// 入参: coverage 覆盖图像, y 行坐标, left 起始列, right 结束列
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// 返回: []byte RGBA像素或空值
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func CoverageRow(coverage image.Image, y, left, right int) []byte {
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buffer, ok := coverage.(*image.RGBA)
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if !ok || y < buffer.Rect.Min.Y || y >= buffer.Rect.Max.Y || left < buffer.Rect.Min.X || right > buffer.Rect.Max.X || left >= right {
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return nil
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}
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start := buffer.PixOffset(left, y)
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return buffer.Pix[start : start+4*(right-left)]
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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 *CompositeBuffers[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 *CompositeBuffers[T]) Release(buffer []T) {
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if len(buffer) == 0 || cap(buffer) > CompositeTileSize*CompositeTileSize {
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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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// Acquire 借用尺寸相同的独占画布，不清空已有像素
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// 入参: rect 输出像素范围
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// 返回: *image.RGBA 当前调用独占的画布
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func (s *RasterBuffers) Acquire(rect image.Rectangle) *image.RGBA {
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for i, stored := range s {
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if stored != nil && stored.Rect == rect {
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s[i] = nil
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return stored
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}
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}
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return image.NewRGBA(rect)
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}
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// Release 归还块容量内的画布，超出容量或空闲槽数量时直接释放
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// 入参: buffer 当前调用借用的画布
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func (s *RasterBuffers) Release(buffer *image.RGBA) {
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if buffer == nil || cap(buffer.Pix) > 4*CompositeTileSize*CompositeTileSize {
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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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