feat(文件拆分): 拆分PDF格式适配模块

internal/codec/pdf/color.go

@@ -0,0 +1,37 @@
+// 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 pdf
+
+import (
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// OutputColor 将合成结果映射到OFD输出，与保留的设备四色对象使用相同显示换算
+// 入参: space 合成空间, values 非预乘分量
+// 返回: [3]float64 显示颜色, error 校准颜色转换错误
+func OutputColor(space *pdfgo.ColorSpace, values [4]float64) ([3]float64, error) {
+	if space.Model == "DeviceCMYK" && !space.Calibrated() {
+		black := 1 - values[3]
+		return [3]float64{(1 - values[0]) * black, (1 - values[1]) * black, (1 - values[2]) * black}, nil
+	}
+	return space.RGB(values[:space.Components()], "RelativeColorimetric")
+}
+
+// NormalBlend 判断混合模式是否为普通覆盖
+// 入参: mode 混合模式
+// 返回: bool 是否普通覆盖
+func NormalBlend(mode pdfgo.Name) bool {
+	return mode == "" || mode == "Normal" || mode == "Compatible"
+}