java 多张jpg合成tif后避免tif文件过大的方法

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这几天突然有个需求要求把之前的通过扫描仪扫出来的jpg图片给合成一个tif文件，乍一看这个需求还是没啥问题的，于是乎直接上网找一个方法下来就好啦，百度“多张jpg合成tif”得到如下方法：

	/*** 合并成一个tif* @param bookFilePaths 要合并的图片集合，字符串为图片的全路径* @param toPath 目的文件夹路径* @param distFileName 合成的文件名（带后缀）*/public static void many2one(List<String> bookFilePaths, String toPath, String distFileName) {if (bookFilePaths != null && bookFilePaths.size() > 0) {File[] files = new File[bookFilePaths.size()];for (int i = 0; i < bookFilePaths.size(); i++) {files[i] = new File(bookFilePaths.get(i));}if (files != null && files.length > 0) {try {ArrayList pages = new ArrayList(files.length - 1);FileSeekableStream[] stream = new FileSeekableStream[files.length];for (int i = 0; i < files.length; i++) {stream[i] = new FileSeekableStream(files[i].getPath());}ParameterBlock pb = (new ParameterBlock());PlanarImage firstPage = JAI.create("stream", stream[0]);for (int i = 1; i < files.length; i++) {PlanarImage page = JAI.create("stream", stream[i]);pages.add(page);}TIFFEncodeParam param = new TIFFEncodeParam();File f = new File(toPath);if (!f.exists()) {f.mkdirs();}OutputStream os = new FileOutputStream(toPath + File.separator + distFileName);ImageEncoder enc = ImageCodec.createImageEncoder("tiff", os, param);param.setExtraImages(pages.iterator());enc.encode(firstPage);for (int i = 0; i < files.length; i++) {stream[i].close();if (files[i].isFile() && files[i].exists()) {files[i].delete();}}os.close();} catch (IOException e) {e.printStackTrace();}}}}

参数意义明确，感觉胜利就在眼前，迅速把图片放上去试一下，结果发现30张300K左右的jpg图片合成完之后却有340M！这个是肯定不接受的。上网找了一个软件来合成这30张jpg大小为9M，与30张的大小之和基本一致。

想了以下几个办法解决：

1.直接压缩340M的tif

2.先压缩jpg再合成tif

3.先把30张jpg转为pdf再转tif

4.重新review方法找原因

第一种方法压缩之后离要求的大小还是相差很大；第二种先压缩再合成也是这样，而且还改变了原jpg的dpi，这种方案也是不行；第三种方案，pdf转tif有问题，不是对于中文pdf支持有问题就是转不出多页tif，也pass；最后一种方案，好好研究了一下TIFFEncodeParam，TIFFField这两个类，先贴成功之后的代码

	public static void many2one(List<String> bookFilePaths, String toPath, String distFileName) {if (bookFilePaths != null && bookFilePaths.size() > 0) {File[] files = new File[bookFilePaths.size()];for (int i = 0; i < bookFilePaths.size(); i++) {files[i] = new File(bookFilePaths.get(i));}if (files != null && files.length > 0) {try {ArrayList pages = new ArrayList(files.length - 1);FileSeekableStream[] stream = new FileSeekableStream[files.length];for (int i = 0; i < files.length; i++) {stream[i] = new FileSeekableStream(files[i].getCanonicalPath());}ParameterBlock pb = (new ParameterBlock());PlanarImage firstPage = JAI.create("stream", stream[0]);for (int i = 1; i < files.length; i++) {PlanarImage page = JAI.create("stream", stream[i]);pages.add(page);}TIFFEncodeParam param = new TIFFEncodeParam();param.setCompression(TIFFEncodeParam.COMPRESSION_JPEG_TTN2);
//					param.setCompression(TIFFEncodeParam.COMPRESSION_DEFLATE);
//					param.setDeflateLevel(9);
//					param.setWriteTiled(true);
//					param.setReverseFillOrder(true);TIFFField[] extras = new TIFFField[4];extras[0] = new TIFFField(262, TIFFField.TIFF_SHORT, 1, (Object) new short[] { 6 });extras[1] = new TIFFField(282, TIFFTag.TIFF_RATIONAL, 1, (Object) new long[][]{{(long) 200, 1}, {0, 0}});  extras[2] = new TIFFField(283, TIFFTag.TIFF_RATIONAL, 1, (Object) new long[][]{{(long) 200, 1}, {0, 0}});extras[3] = new TIFFField(258, TIFFField.TIFF_SHORT, 1, (Object) new char[] { 8 });param.setExtraFields(extras);param.setExtraImages(pages.iterator());File f = new File(toPath);if (!f.exists()) {f.mkdirs();}OutputStream os = new FileOutputStream(toPath + File.separator + distFileName);ImageEncoder enc = ImageCodec.createImageEncoder("tiff", os, param);enc.encode(firstPage);os.close();System.out.println("over");} catch (IOException e) {e.printStackTrace();}}}}

TIFFEncodeParam类

https://docs.oracle.com/cd/E17802_01/products/products/java-media/jai/forDevelopers/jai-apidocs/com/sun/media/jai/codec/TIFFEncodeParam.html#COMPRESSION_DEFLATE