add compress raw data

internal/pkg/epubzip/image.go

@@ -66,3 +66,39 @@ func CompressImage(filename string, format string, img image.Image, quality int)
 		cdata.Bytes(),
 	}, nil
 }
+
+func CompressRaw(filename string, uncompressedData []byte) (Image, error) {
+	var (
+		cdata bytes.Buffer
+		err   error
+	)
+	wcdata, err := flate.NewWriter(&cdata, flate.BestCompression)
+	if err != nil {
+		return Image{}, err
+	}
+
+	_, err = wcdata.Write(uncompressedData)
+	if err != nil {
+		return Image{}, err
+	}
+
+	err = wcdata.Close()
+	if err != nil {
+		return Image{}, err
+	}
+
+	t := time.Now()
+	//goland:noinspection GoDeprecation
+	return Image{
+		&zip.FileHeader{
+			Name:               filename,
+			CompressedSize64:   uint64(cdata.Len()),
+			UncompressedSize64: uint64(len(uncompressedData)),
+			CRC32:              crc32.Checksum(uncompressedData, crc32.IEEETable),
+			Method:             zip.Deflate,
+			ModifiedTime:       uint16(t.Second()/2 + t.Minute()<<5 + t.Hour()<<11),
+			ModifiedDate:       uint16(t.Day() + int(t.Month())<<5 + (t.Year()-1980)<<9),
+		},
+		cdata.Bytes(),
+	}, nil
+}