Java 如何在图像中设置 DPI 信息？
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How to set DPI information in an image?
提问by David Koelle
I have an application that I want to export high-resolution (or rather, high pixel density?) images for printing - for example, I want images that print at 250 dots per inch (DPI), instead of the default, which I understand to be 72 DPI.
我有一个应用程序，我想导出高分辨率（或更确切地说，高像素密度？）图像进行打印 - 例如，我想要以每英寸 250 点 (DPI) 打印的图像，而不是我理解的默认值为 72 DPI。
I'm using a BufferedImage with a Graphics2D object to draw the image, then ImageIO.write() to save the image.
我使用带有 Graphics2D 对象的 BufferedImage 来绘制图像，然后使用 ImageIO.write() 来保存图像。
Any idea how I can set the DPI?
知道如何设置 DPI 吗？
采纳答案by Peter Kofler
Kurt's answer showed the way, still it took me quite some time to get it run, so here is the code that sets DPI when saving a PNG. There is a lot to do to get the proper writers and such...
Kurt 的回答指明了方向，但我还是花了很长时间才让它运行，所以这里是保存 PNG 时设置 DPI 的代码。要找到合适的作家，还有很多工作要做……
private BufferedImage gridImage;
...
private void saveGridImage(File output) throws IOException {
output.delete();
final String formatName = "png";
for (Iterator<ImageWriter> iw = ImageIO.getImageWritersByFormatName(formatName); iw.hasNext();) {
ImageWriter writer = iw.next();
ImageWriteParam writeParam = writer.getDefaultWriteParam();
ImageTypeSpecifier typeSpecifier = ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_RGB);
IIOMetadata metadata = writer.getDefaultImageMetadata(typeSpecifier, writeParam);
if (metadata.isReadOnly() || !metadata.isStandardMetadataFormatSupported()) {
continue;
}
setDPI(metadata);
final ImageOutputStream stream = ImageIO.createImageOutputStream(output);
try {
writer.setOutput(stream);
writer.write(metadata, new IIOImage(gridImage, null, metadata), writeParam);
} finally {
stream.close();
}
break;
}
}
private void setDPI(IIOMetadata metadata) throws IIOInvalidTreeException {
// for PMG, it's dots per millimeter
double dotsPerMilli = 1.0 * DPI / 10 / INCH_2_CM;
IIOMetadataNode horiz = new IIOMetadataNode("HorizontalPixelSize");
horiz.setAttribute("value", Double.toString(dotsPerMilli));
IIOMetadataNode vert = new IIOMetadataNode("VerticalPixelSize");
vert.setAttribute("value", Double.toString(dotsPerMilli));
IIOMetadataNode dim = new IIOMetadataNode("Dimension");
dim.appendChild(horiz);
dim.appendChild(vert);
IIOMetadataNode root = new IIOMetadataNode("javax_imageio_1.0");
root.appendChild(dim);
metadata.mergeTree("javax_imageio_1.0", root);
}
回答by David Koelle
First Google link:
第一个谷歌链接：
http://www.tracemodeler.com/articles/aging-bugs-and-setting-dpi-with-java-image-io/
http://www.tracemodeler.com/articles/aging-bugs-and-setting-dpi-with-java-image-io/
And it looks like it has the information you need.
看起来它有你需要的信息。
回答by David Koelle
I found this thread on the Oracle Community Directory:
我在 Oracle Community Directory 上找到了这个帖子：
https://community.oracle.com/thread/1265028?tstart=0
https://community.oracle.com/thread/1265028?tstart=0
So, looks like it's not as easy as image.setDPI(200, 400).
所以，看起来不像image.setDPI(200, 400).
回答by rj27
i am using this code for tiff file in my project and it works well..
我在我的项目中将此代码用于 tiff 文件，它运行良好..
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.ImageIO;
import javax.media.jai.NullOpImage;
import javax.media.jai.OpImage;
import javax.media.jai.PlanarImage;
import com.sun.media.jai.codec.FileSeekableStream;
import com.sun.media.jai.codec.ImageCodec;
import com.sun.media.jai.codec.ImageDecoder;
import com.sun.media.jai.codec.ImageEncoder;
import com.sun.media.jai.codec.SeekableStream;
import com.sun.media.jai.codec.TIFFEncodeParam;
import com.sun.media.jai.codec.TIFFField;
class SetDDPI
{
static void tiff_Maker(List<BufferedImage> output, String result) throws IOException
{
TIFFEncodeParam params = new TIFFEncodeParam();
OutputStream out = new FileOutputStream(result);
List<BufferedImage> imageList = new ArrayList<BufferedImage>();
for (int i = 1; i < output.size(); i++)
{
imageList.add(output.get(i));
}
params.setWriteTiled(true);
params.setCompression(TIFFEncodeParam.COMPRESSION_GROUP4);
params.setExtraImages(imageList.iterator());
TIFFField[] extras = new TIFFField[2];
extras[0] = new TIFFField(282, TIFFField.TIFF_RATIONAL, 1, (Object) new long[][] { { (long) 300, (long) 1 },
{ (long) 0, (long) 0 } });
extras[1] = new TIFFField(283, TIFFField.TIFF_RATIONAL, 1, (Object) new long[][] { { (long) 300, (long) 1 },
{ (long) 0, (long) 0 } });
params.setExtraFields(extras);
ImageEncoder encoder = ImageCodec.createImageEncoder("tiff", out, params);
encoder.encode(output.get(0));
out.close();
}
static List<BufferedImage> tiff_Extractor(File tiff) throws IOException
{
List<BufferedImage> images = new ArrayList<BufferedImage>();
SeekableStream ss = new FileSeekableStream(tiff);
ImageDecoder decoder = ImageCodec.createImageDecoder("tiff", ss, null);
int numPages = decoder.getNumPages();
for (int j = 0; j < numPages; j++)
{
PlanarImage op = new NullOpImage(decoder.decodeAsRenderedImage(j), null, null, OpImage.OP_IO_BOUND);
images.add(op.getAsBufferedImage());
}
return images;
}
}
this is to set 300 DPI of Tiff image. you can change it according to your need.
这是设置 300 DPI 的 Tiff 图像。您可以根据需要更改它。
extras[0] = new TIFFField(282, TIFFField.TIFF_RATIONAL, 1, (Object) new
long[][] { { (long) 300, (long) 1 },{ (long) 0, (long) 0 } });
extras[1] = new TIFFField(283, TIFFField.TIFF_RATIONAL, 1, (Object) new
long[][] { { (long) 300, (long) 1 },{ (long) 0, (long) 0 } });
回答by XIII-th
Seting up TIFF DPI
设置 TIFF DPI
If you want to set dpi for TIFF, try to do that by next steps:
如果要为 TIFF 设置 dpi，请尝试按照以下步骤进行操作：
private static IIOMetadata createMetadata(ImageWriter writer, ImageWriteParam writerParams, int resolution) throws
IIOInvalidTreeException
{
// Get default metadata from writer
ImageTypeSpecifier type = ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_BYTE_GRAY);
IIOMetadata meta = writer.getDefaultImageMetadata(type, writerParams);
// Convert default metadata to TIFF metadata
TIFFDirectory dir = TIFFDirectory.createFromMetadata(meta);
// Get {X,Y} resolution tags
BaselineTIFFTagSet base = BaselineTIFFTagSet.getInstance();
TIFFTag tagXRes = base.getTag(BaselineTIFFTagSet.TAG_X_RESOLUTION);
TIFFTag tagYRes = base.getTag(BaselineTIFFTagSet.TAG_Y_RESOLUTION);
// Create {X,Y} resolution fields
TIFFField fieldXRes = new TIFFField(tagXRes, TIFFTag.TIFF_RATIONAL, 1, new long[][] { { resolution, 1 } });
TIFFField fieldYRes = new TIFFField(tagYRes, TIFFTag.TIFF_RATIONAL, 1, new long[][] { { resolution, 1 } });
// Add {X,Y} resolution fields to TIFFDirectory
dir.addTIFFField(fieldXRes);
dir.addTIFFField(fieldYRes);
// Add unit field to TIFFDirectory (change to RESOLUTION_UNIT_CENTIMETER if necessary)
dir.addTIFFField(new TIFFField(base.getTag(BaselineTIFFTagSet.TAG_RESOLUTION_UNIT), BaselineTIFFTagSet.RESOLUTION_UNIT_INCH));
// Return TIFF metadata so it can be picked up by the IIOImage
return dir.getAsMetadata();
}
Also, similar way you can setting up any TIFF tag.
此外，您可以通过类似的方式设置任何 TIFF 标签。
Read more at the source
在源头阅读更多
