将 dpi 元数据写入 Java 中的 jpeg 图像
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Write dpi metadata to a jpeg image in Java
提问by dasp
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.
我正在尝试以编程方式设置 Java 中 jpeg 图像的 dpi 元数据。图像的来源是扫描仪，因此我从 TWAIN 获得了水平/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) 保存到 JPEG 文件，但它忽略了我通过 IIOMetadata 指定的 X/Y密度信息。任何建议我做错了什么？
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!
谢谢！
回答by
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:
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.set the meta data as
IOMetadataof theIOImage. These meta data are used by JPEGImageWriter. The correct write call then isimageWriter.write(null, new IIOImage(F_scaledImg, null, data), jpegParams);
树没有直接映射到 IOMetaData。要应用树中的数据，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);不要在 write 调用中使用元数据作为第一个参数。见
JPEGImageWriter#write(IIOMetaData, IIOImage, ImageWriteParam)。如果 streamMetaData 不为 NULL，则会生成警告 (WARNING_STREAM_METADATA_IGNORED)。设置的元数据
IOMetadata的IOImage。这些元数据由 JPEGImageWriter 使用。正确的写调用然后是imageWriter.write(null, new IIOImage(F_scaledImg, null, data), jpegParams);
回答by branchgabriel
I would seem this could be a bug.
我认为这可能是一个错误。
I found this post from a few google searches
我从一些谷歌搜索中找到了这篇文章
Apparently there are alot more that point to a bug as well.
显然还有很多指向错误的地方。
The post above talks about using JMagick as a third party work around.
上面的帖子讨论了使用 JMagick 作为第三方解决方法。
