使用Java将dpi元数据写入jpeg图像

I am trying to programatically set the dpi metadata of an jpeg image in Java. The source of the image is a scanner, so I get the horizontal/vertical resolution from TWAIN, along with the image raw data. I'd like to save this info for better print results.

我试图以编程方式在Java中设置jpeg图像的dpi元数据。图像的来源是扫描仪,因此我从TWAIN获得水平/垂直分辨率以及图像原始数据。我想保存此信息以获得更好的打印效果。

Here's the code I have so far. It saves the raw image (byteArray) to a JPEG file, but it ignores the X/Ydensity information I specify via IIOMetadata. Any advice what I'm doing wrong?

这是我到目前为止的代码。它将原始图像(byteArray)保存为JPEG文件,但忽略了我通过IIOMetadata指定的X / Ydensity信息。我有什么建议我做错了吗?

Any other solution (third-party library, etc) would be welcome too.

任何其他解决方案(第三方库等)也将受到欢迎。

import java.awt.image.BufferedImage;
import java.awt.image.WritableRaster;
import java.io.File;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageTypeSpecifier;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.plugins.jpeg.JPEGImageWriteParam;
import javax.imageio.stream.ImageOutputStream    

import org.w3c.dom.Element;    
import com.sun.imageio.plugins.jpeg.JPEGImageWriter;

public boolean saveJpeg(int[] byteArray, int width, int height, int dpi, String file)
{
    BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

    WritableRaster wr = bufferedImage.getRaster();
    wr.setPixels(0, 0, width, height, byteArray);

    try
    {           
        // Image writer 
        JPEGImageWriter imageWriter = (JPEGImageWriter) ImageIO.getImageWritersBySuffix("jpeg").next();
        ImageOutputStream ios = ImageIO.createImageOutputStream(new File(file));
        imageWriter.setOutput(ios);

        // Compression
        JPEGImageWriteParam jpegParams = (JPEGImageWriteParam) imageWriter.getDefaultWriteParam();
        jpegParams.setCompressionMode(JPEGImageWriteParam.MODE_EXPLICIT);
        jpegParams.setCompressionQuality(0.85f);

        // Metadata (dpi)
        IIOMetadata data = imageWriter.getDefaultImageMetadata(new ImageTypeSpecifier(bufferedImage), jpegParams);
        Element tree = (Element)data.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));
        jfif.setAttribute("resUnits", "1"); // density is dots per inch         

        // Write and clean up
        imageWriter.write(data, new IIOImage(bufferedImage, null, null), jpegParams);
        ios.close();
        imageWriter.dispose();
    }
    catch (Exception e)
    {
       return false;
    }

    return true;
}

Thanks!

2 个解决方案

#1

Some issues that were not considered here:

这里没有考虑的一些问题:

The tree is not directly mapped to the IOMetaData. To apply data from tree, add following call after setting the densities and raster parameters:

树未直接映射到IOMetaData。要从树应用数据,请在设置密度和栅格参数后添加以下调用:
```
data.setFromTree("javax_imageio_jpeg_image_1.0", tree);
```
don't use the meta data as first parameter in the write call. See JPEGImageWriter#write(IIOMetaData, IIOImage, ImageWriteParam). If streamMetaData is not NULL, a warning (WARNING_STREAM_METADATA_IGNORED) will be generated.

不要将元数据用作写调用中的第一个参数。请参阅JPEGImageWriter#write(IIOMetaData,IIOImage,ImageWriteParam)。如果streamMetaData不为NULL,则将生成警告(WARNING_STREAM_METADATA_IGNORED)。
set the meta data as IOMetadata of the IOImage. These meta data are used by JPEGImageWriter. The correct write call then is

将元数据设置为IOImage的IOMetadata。 JPEGImageWriter使用这些元数据。然后是正确的写入调用
```
imageWriter.write(null, new IIOImage(F_scaledImg, null, data), jpegParams);
```

#2

I would seem this could be a bug.

我觉得这可能是个错误。

I found this post from a few google searches

我从一些谷歌搜索中发现了这篇文章

Apparently there are alot more that point to a bug as well.

显然,还有更多指向错误。

The post above talks about using JMagick as a third party work around.

上面的帖子讨论了如何使用JMagick作为第三方解决方案。

#1