Replacing the deprecated Java JPEG classes for Java 7

最新推荐文章于 2021-02-23 18:39:08 发布

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最新推荐文章于 2021-02-23 18:39:08 发布

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原文链接：http://www.cnblogs.com/sanshizi/p/4590618.html

本文探讨了Java7更新中关于JPEG图像处理的变化，包括旧JPEG类的移除及新ImageIO类的使用，提供了从旧版到新版的代码转换示例。

[src: https://blog.idrsolutions.com/2012/05/replacing-the-deprecated-java-jpeg-classes-for-java-7/]

In the early days of Java, Sun produced a really handy set of classes to handle JPEG images. These included some really nifty little features like the ability to easily set the amount of compression and the resolution. When ImageIO came along, the class was deprecated. This means that it is still in Java but not guaranteed to be in any later releases. ImageIO was more complicated to use for JPEG images and we felt the earlier code produced better results so we continued to use it.

I have been checking our code against the new Java 7 (release 4) build for the Mac and it now appears that the old JPEG classes have finally been removed. So I have updated my code to use ImageIO. Here is my updated version with both old and new versions so you can see the changes if you are still using these classes.

public static void saveAsJPEG(String jpgFlag,BufferedImage image_to_save, float JPEGcompression, FileOutputStream fos) throws IOException {
 
    //useful documentation at http://docs.oracle.com/javase/7/docs/api/javax/imageio/metadata/doc-files/jpeg_metadata.html
    //useful example program at http://johnbokma.com/java/obtaining-image-metadata.html to output JPEG data
 
    //old jpeg class
    //com.sun.image.codec.jpeg.JPEGImageEncoder jpegEncoder = com.sun.image.codec.jpeg.JPEGCodec.createJPEGEncoder(fos);
    //com.sun.image.codec.jpeg.JPEGEncodeParam jpegEncodeParam = jpegEncoder.getDefaultJPEGEncodeParam(image_to_save);
 
    // Image writer
    JPEGImageWriter imageWriter = (JPEGImageWriter) ImageIO.getImageWritersBySuffix(“jpeg”).next();
    ImageOutputStream ios = ImageIO.createImageOutputStream(fos);
    imageWriter.setOutput(ios);
 
    //and metadata
    IIOMetadata imageMetaData = imageWriter.getDefaultImageMetadata(new ImageTypeSpecifier(image_to_save), null);
 
    if (jpgFlag != null){
 
        int dpi = 96;
 
        try {
            dpi = Integer.parseInt(jpgFlag);
        } catch (Exception e) {
            e.printStackTrace();
        }
 
        //old metadata
        //jpegEncodeParam.setDensityUnit(com.sun.image.codec.jpeg.JPEGEncodeParam.DENSITY_UNIT_DOTS_INCH);
        //jpegEncodeParam.setXDensity(dpi);
        //jpegEncodeParam.setYDensity(dpi);
 
        //new metadata
        Element tree = (Element) imageMetaData.getAsTree(“javax_imageio_jpeg_image_1.0?);
        Element jfif = (Element)tree.getElementsByTagName(“app0JFIF”).item(0);
        jfif.setAttribute(“Xdensity”, Integer.toString(dpi));
        jfif.setAttribute(“Ydensity”, Integer.toString(dpi));
 
    }
 
    if(JPEGcompression>=0 && JPEGcompression<=1f){
 
        //old compression
        //jpegEncodeParam.setQuality(JPEGcompression,false);
 
        // new Compression
        JPEGImageWriteParam jpegParams = (JPEGImageWriteParam) imageWriter.getDefaultWriteParam();
        jpegParams.setCompressionMode(JPEGImageWriteParam.MODE_EXPLICIT);
        jpegParams.setCompressionQuality(JPEGcompression);
 
    }
 
    //old write and clean
    //jpegEncoder.encode(image_to_save, jpegEncodeParam);
 
    //new Write and clean up
    imageWriter.write(imageMetaData, new IIOImage(image_to_save, null, null), null);
    ios.close();
    imageWriter.dispose();
 
}

　　Otherwise, Java 7 looks to be a definite progression over Java 6. What do you think of it?

转载于:https://www.cnblogs.com/sanshizi/p/4590618.html