mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 15:06:46 +08:00
230 lines
7.9 KiB
Go
230 lines
7.9 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 (
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"bytes"
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"compress/zlib"
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"context"
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"encoding/binary"
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"fmt"
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"image"
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"image/color"
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"math"
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baseimage "github.com/xiaoqidun/ofdgo/internal/base/image"
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"github.com/xiaoqidun/pdfgo"
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)
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// StencilImage 按当前填充色读取模板图像，不分配整幅彩色样本
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type StencilImage struct {
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Source image.Image
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Fill color.NRGBA64
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}
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// NativeImage 按源像素输出原生过程色，不分配完整显示颜色缓冲
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type NativeImage struct {
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Source *pdfgo.ImageProcess
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Space *pdfgo.ColorSpace
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}
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// EncodeCMYKTIFF 将直接四色图像保存为十六位无损TIFF，不经过显示颜色转换
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// 入参: ctx 取消上下文, source PDF源图像
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// 返回: []byte 含ICC和非预乘透明度的TIFF，非四色图像为nil, error 解码或编码错误
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func EncodeCMYKTIFF(ctx context.Context, source *pdfgo.Image) ([]byte, error) {
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if ctx == nil || source == nil {
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return nil, fmt.Errorf("missing CMYK image context or source")
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}
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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if source.ImageMask {
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return nil, nil
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}
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family, err := source.ColorSpaceFamily()
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if err != nil || family != "DeviceCMYK" && family != "ICCBased" {
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return nil, err
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}
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if family == "ICCBased" {
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count, err := source.ColorSpaceComponents()
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if err != nil || count != 4 {
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return nil, err
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}
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}
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components, err := source.DecodeComponentsViewContext(ctx)
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if err != nil {
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return nil, err
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}
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if components.Space == nil || components.Space.Model != "DeviceCMYK" || components.Space.Components() != 4 || components.ColorantSpace != nil {
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return nil, nil
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}
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bounds := components.Rect
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width, height := bounds.Dx(), bounds.Dy()
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if width <= 0 || height <= 0 || width > int(^uint(0)>>1)/10 || uint64(width) > uint64(^uint32(0))/10 || uint64(height) > uint64(^uint32(0)) {
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return nil, fmt.Errorf("invalid CMYK TIFF dimensions")
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}
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profile := components.Space.ICCProfile(source.Intent)
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count := 12
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if len(profile) != 0 {
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count++
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}
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bitsOffset := uint64(8 + 2 + count*12 + 4)
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profileOffset := bitsOffset + 10
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stripOffset := (profileOffset + uint64(len(profile)) + 1) &^ uint64(1)
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if stripOffset > uint64(^uint32(0)) {
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return nil, fmt.Errorf("CMYK TIFF profile exceeds size limit")
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}
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var compressed bytes.Buffer
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writer := zlib.NewWriter(&compressed)
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row := make([]byte, width*10)
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for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
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for x := bounds.Min.X; x < bounds.Max.X; x++ {
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if (x-bounds.Min.X)%1024 == 0 {
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if err := ctx.Err(); err != nil {
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writer.Close()
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return nil, err
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}
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}
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values, alpha := components.ValuesAt(x, y)
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pixel := row[(x-bounds.Min.X)*10:]
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for channel, value := range [5]float64{values[0], values[1], values[2], values[3], alpha} {
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if math.IsNaN(value) || math.IsInf(value, 0) || value < 0 || value > 1 {
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writer.Close()
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return nil, fmt.Errorf("invalid CMYK TIFF component")
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}
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binary.LittleEndian.PutUint16(pixel[channel*2:], uint16(math.Round(value*65535)))
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}
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}
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if _, err := writer.Write(row); err != nil {
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writer.Close()
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return nil, err
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}
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if stripOffset+uint64(compressed.Len()) > uint64(^uint32(0)) {
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writer.Close()
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return nil, fmt.Errorf("CMYK TIFF exceeds size limit")
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}
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}
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if err := writer.Close(); err != nil {
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return nil, err
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}
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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total := stripOffset + uint64(compressed.Len())
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if total > uint64(^uint32(0)) || total > uint64(int(^uint(0)>>1)) {
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return nil, fmt.Errorf("CMYK TIFF exceeds size limit")
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}
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data := make([]byte, int(total))
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copy(data, "II")
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binary.LittleEndian.PutUint16(data[2:], 42)
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binary.LittleEndian.PutUint32(data[4:], 8)
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binary.LittleEndian.PutUint16(data[8:], uint16(count))
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entries := [][4]uint32{
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{256, 4, 1, uint32(width)}, {257, 4, 1, uint32(height)},
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{258, 3, 5, uint32(bitsOffset)}, {259, 3, 1, 8}, {262, 3, 1, 5},
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{273, 4, 1, uint32(stripOffset)}, {277, 3, 1, 5}, {278, 4, 1, uint32(height)},
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{279, 4, 1, uint32(compressed.Len())}, {284, 3, 1, 1}, {332, 3, 1, 1}, {338, 3, 1, 2},
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}
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if len(profile) != 0 {
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entries = append(entries, [4]uint32{34675, 7, uint32(len(profile)), uint32(profileOffset)})
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}
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for i, entry := range entries {
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p := data[10+i*12:]
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binary.LittleEndian.PutUint16(p, uint16(entry[0]))
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binary.LittleEndian.PutUint16(p[2:], uint16(entry[1]))
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binary.LittleEndian.PutUint32(p[4:], entry[2])
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binary.LittleEndian.PutUint32(p[8:], entry[3])
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}
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for i := range 5 {
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binary.LittleEndian.PutUint16(data[int(bitsOffset)+2*i:], 16)
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}
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copy(data[int(profileOffset):], profile)
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copy(data[int(stripOffset):], compressed.Bytes())
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return data, nil
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}
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// ColorModel 保留填充色和模板的有效采样精度
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// 返回: color.Model 非预乘颜色模型
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func (s *StencilImage) ColorModel() color.Model {
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model := s.Source.ColorModel()
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if s.Fill.R%257 == 0 && s.Fill.G%257 == 0 && s.Fill.B%257 == 0 && (model == color.GrayModel || model == color.NRGBAModel || model == color.RGBAModel) {
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return color.NRGBAModel
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}
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return color.NRGBA64Model
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}
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// Bounds 返回模板图像的采样边界
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// 返回: image.Rectangle 图像边界
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func (s *StencilImage) Bounds() image.Rectangle { return s.Source.Bounds() }
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// At 以模板灰度计算填充覆盖率，不重复变换颜色
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// 入参: x 横向坐标, y 纵向坐标
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// 返回: color.Color 非预乘颜色
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func (s *StencilImage) At(x, y int) color.Color {
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return s.NRGBA64At(x, y)
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}
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// NRGBA64At 直接读取模板覆盖率，保留填充色的有效精度
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// 入参: x 横向坐标, y 纵向坐标
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// 返回: color.NRGBA64 非预乘颜色
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func (s *StencilImage) NRGBA64At(x, y int) color.NRGBA64 {
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if !image.Pt(x, y).In(s.Bounds()) {
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return color.NRGBA64{}
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}
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gray := baseimage.NRGBA64At(s.Source, x, y)
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pixel := s.Fill
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pixel.A = uint16(65535 - gray.R)
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return pixel
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}
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// ColorModel 保留16位原生分量与源透明度
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// 返回: color.Model 非预乘颜色模型
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func (s *NativeImage) ColorModel() color.Model { return color.NRGBA64Model }
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// Bounds 返回源图像的完整采样边界
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// 返回: image.Rectangle 原始像素边界
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func (s *NativeImage) Bounds() image.Rectangle { return s.Source.Bounds() }
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// At 获取按OFD输出映射的原生颜色
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// 入参: x 横坐标, y 纵坐标
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// 返回: color.Color 非预乘颜色
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func (s *NativeImage) At(x, y int) color.Color { return s.NRGBA64At(x, y) }
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// NRGBA64At 按原始精度转换设备过程色，不进行页面采样或备用变换
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// 入参: x 横坐标, y 纵坐标
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// 返回: color.NRGBA64 非预乘颜色
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func (s *NativeImage) NRGBA64At(x, y int) color.NRGBA64 {
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if !image.Pt(x, y).In(s.Bounds()) {
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return color.NRGBA64{}
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}
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values, alpha := s.Source.ValuesAt(x, y)
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rgb, _ := OutputColor(s.Space, values)
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return color.NRGBA64{R: uint16(math.Round(rgb[0] * 65535)), G: uint16(math.Round(rgb[1] * 65535)), B: uint16(math.Round(rgb[2] * 65535)), A: uint16(math.Round(alpha * 65535))}
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}
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// ImageProcessColorants 识别可在四色设备上直接绘制的专色色料
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// 入参: image PDF图像
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// 返回: [4]bool 参与绘制的四色通道, bool 是否全部属于印刷原色, error 色空间错误
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func ImageProcessColorants(image *pdfgo.Image) ([4]bool, bool, error) {
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source, err := image.ColorantSpace()
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if err != nil {
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return [4]bool{}, false, err
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}
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space := &pdfgo.ColorSpace{Model: "DeviceCMYK"}
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process := source.PrepareProcess(&pdfgo.ColorantDevice{Space: space}, space, false)
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mask := process.Mask()
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return mask, mask != ([4]bool{}), nil
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}
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