feat(归并文件): 归并根包文件

ofdgo_compression_images.go

@@ -15,10 +15,17 @@
 package ofdgo
 
 import (
+	"bytes"
 	"context"
+	"encoding/binary"
+	"errors"
 	"fmt"
 	"image"
+	"io"
 	"math"
+
+	baseimage "github.com/xiaoqidun/ofdgo/internal/base/image"
+	"github.com/xiaoqidun/pdfgo"
 )
 
 // compressionPatternImageLimit 限制底纹尺寸分析的变换组合数，超限时保留原图尺寸
@@ -397,3 +404,173 @@ func (v *compressionImages) patternImages(color *FillColor, object Matrix) error
 	}
 	return nil
 }
+
+// outputImageFormat 识别可由资源压缩生成的图片格式
+// 入参: data 图片编码
+// 返回: string 标准资源格式，未识别时为空
+func outputImageFormat(data []byte) string {
+	if baseimage.IsJPEG(data) {
+		return "JPEG"
+	}
+	if baseimage.IsPNG(data) {
+		return "PNG"
+	}
+	return ""
+}
+
+// optimizeImageResource 优化可完整保留的BMP及TIFF，复用图像压缩和降采样策略
+// 原始模式及无法保留的色彩配置不转换，仅采用小于原始编码的结果
+// 入参: ctx 取消上下文, data 图片编码, options 压缩选项, size 像素需求
+// 返回: []byte 图片编码，可能引用输入, error 解码、编码或取消错误
+func optimizeImageResource(ctx context.Context, data []byte, options CompressionOptions, size image.Point) ([]byte, error) {
+	if err := options.Validate(); err != nil {
+		return nil, err
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	if options.Mode != CompressionUnchanged && baseimage.IsTIFF(data) {
+		return optimizeTIFFResource(ctx, data, options, size)
+	}
+	if options.Mode == CompressionUnchanged || !bytes.HasPrefix(data, []byte("BM")) {
+		return pdfgo.OptimizeImageResource(ctx, data, options, size)
+	}
+	return optimizeBMPResource(ctx, data, options, size)
+}
+
+// optimizeBMPResource 压缩可保留色彩与密度的位图，未知元数据及高精度位域保持原样
+// 入参: ctx 取消上下文, data BMP编码, options 压缩选项, size 像素需求
+// 返回: []byte 图片编码, error 解码、编码或取消错误
+func optimizeBMPResource(ctx context.Context, data []byte, options CompressionOptions, size image.Point) ([]byte, error) {
+	offset, width, height, depth, compression, err := baseimage.ParseBMPHeader(data)
+	if err != nil {
+		return data, nil
+	}
+	if height < 0 {
+		height = -height
+	}
+	if int64(width)*int64(height) > outputOptimizationBufferLimit/4 || compression != 0 && compression != 3 {
+		return data, nil
+	}
+	header := binary.LittleEndian.Uint32(data[14:18])
+	if header != 40 && header != 108 && header != 124 {
+		return data, nil
+	}
+	if header >= 108 && binary.LittleEndian.Uint32(data[70:74]) != 0x73524742 {
+		return data, nil
+	}
+	if header == 124 && (binary.LittleEndian.Uint32(data[122:126]) != 0 || binary.LittleEndian.Uint32(data[126:130]) != 0 || binary.LittleEndian.Uint32(data[130:134]) != 0) {
+		return data, nil
+	}
+	stride := (int64(width)*int64(depth) + 31) / 32 * 4
+	if int64(offset)+stride*int64(height) != int64(len(data)) {
+		return data, nil
+	}
+	density, ok := baseimage.BMPDensity(data)
+	if !ok {
+		return data, nil
+	}
+	if depth == 16 || depth == 32 {
+		masks, err := baseimage.BMPColorMasks(data, offset, depth, compression)
+		if err != nil {
+			return data, nil
+		}
+		if options.Mode == CompressionLossless {
+			for _, mask := range masks {
+				if mask.Max > 255 {
+					return data, nil
+				}
+			}
+		}
+	}
+	var pixels image.Image
+	if depth == 16 || compression == 3 {
+		pixels, err = baseimage.DecodeBMPContext(ctx, data)
+	} else {
+		pixels, _, err = image.Decode(imageInput{ReadCloser: io.NopCloser(bytes.NewReader(data)), ctx: ctx})
+	}
+	if err != nil {
+		return nil, err
+	}
+	return optimizeRasterResource(ctx, data, pixels, options, size, density)
+}
+
+// optimizeRasterResource 编码已解码的资源图片，同步降采样后的像素密度，仅采用更小结果
+// 先降采样再编码，绝对密度按最终尺寸量化，相对密度保留精确比例
+// 有密度时保留PNG，未知密度按最终像素选择编码格式
+// 入参: ctx 取消上下文, data 原编码, pixels 像素, options 压缩选项, size 像素需求, density 像素密度
+// 返回: []byte 图片编码, error 编码或取消错误
+func optimizeRasterResource(ctx context.Context, data []byte, pixels image.Image, options CompressionOptions, size image.Point, density baseimage.Density) ([]byte, error) {
+	hasDensity := density.X != 0 || density.Y != 0
+	before := pixels.Bounds().Size()
+	if options.Mode == CompressionLossy {
+		var err error
+		pixels, err = pdfgo.ResizeImage(ctx, pixels, size)
+		if err != nil {
+			return nil, err
+		}
+	}
+	var ok bool
+	density, ok = density.Scale(before, pixels.Bounds().Size())
+	if !ok {
+		return data, ctx.Err()
+	}
+	var candidate []byte
+	var err error
+	if hasDensity {
+		var encoded bytes.Buffer
+		err = pdfgo.EncodePNGWithOptions(ctx, &encoded, pixels, options)
+		candidate = encoded.Bytes()
+	} else {
+		candidate, err = pdfgo.EncodeImageResource(ctx, pixels, options)
+	}
+	if err != nil {
+		if errors.Is(err, io.ErrShortBuffer) {
+			return data, ctx.Err()
+		}
+		return nil, err
+	}
+	if hasDensity {
+		if len(candidate) > outputOptimizationBufferLimit-baseimage.PNGDensityChunkSize {
+			return data, ctx.Err()
+		}
+		candidate, ok = baseimage.WithPNGDensity(candidate, density)
+		if !ok {
+			return data, ctx.Err()
+		}
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	if len(candidate) < len(data) {
+		return candidate, nil
+	}
+	return data, nil
+}
+
+// optimizeTIFFResource 压缩单目录TIFF，保留方向、透明度、采样精度及像素密度
+// 主图或单个瓦片的预计缓冲超限时保留原编码
+// 入参: ctx 取消上下文, data TIFF编码, options 压缩选项, size 显示像素需求
+// 返回: []byte 图片编码，不可完整转换时保留原文, error 编码或取消错误
+func optimizeTIFFResource(ctx context.Context, data []byte, options CompressionOptions, size image.Point) ([]byte, error) {
+	layout, err := baseimage.ReadTIFFLayoutContext(ctx, bytes.NewReader(data))
+	if err != nil {
+		return data, ctx.Err()
+	}
+	pixelSize := int64(layout.DecodedPixelBytes())
+	if int64(layout.Width) > outputOptimizationBufferLimit/pixelSize/int64(layout.Height) {
+		return data, ctx.Err()
+	}
+	if layout.TileWidth != 0 && int64(layout.TileWidth) > outputOptimizationBufferLimit/pixelSize/int64(layout.TileHeight) {
+		return data, ctx.Err()
+	}
+	density, ok := baseimage.TIFFConversionDensity(data, layout)
+	if !ok {
+		return data, ctx.Err()
+	}
+	pixels, err := baseimage.DecodeTIFF(ctx, data, layout)
+	if err != nil {
+		return data, ctx.Err()
+	}
+	return optimizeRasterResource(ctx, data, pixels, options, size, density)
+}