所谓图片元数据,就是除了我们肉眼看到的图片内容外,隐藏在这些内容背后的一些技术数据。
本文介绍如何使用Java代码将一张图片的隐藏信息读取出来。
首先不需要下载任何额外的Java库,用JDK自带的库就能工作。
import java.io.ByteArrayInputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import javax.imageio.ImageIO;import javax.imageio.ImageReader;import javax.imageio.metadata.IIOMetadata;import javax.imageio.metadata.IIOMetadataNode;import org.w3c.dom.NamedNodeMap;import org.w3c.dom.Node;import org.w3c.dom.NodeList;import com.sun.imageio.plugins.png.PNGMetadata; 新建一个Java类,这个类的main方法也是非常直接的:static public void main(String[] arg) throws IOException{byte[] content = getContent("C:\Users\i042416\Desktop\test\clipboard1.png"); readCustomData(content); }
首先把桌面上名叫clipboard1.png的图片文件的内容读到字节数组content中。
getContent方法的代码:
一张png图片的元数据,散布在下面这些节点里:
printNode(pngmeta.getStandardChromaNode()); printNode(pngmeta.getStandardCompressionNode()); printNode(pngmeta.getStandardDataNode()); printNode(pngmeta.getStandardDimensionNode()); printNode(pngmeta.getStandardDocumentNode()); printNode(pngmeta.getStandardTextNode()); printNode(pngmeta.getStandardTransparencyNode());
通过printNode打印出来:
printNode方法的源代码:
打印出来的元数据:
如果大家想要复制粘贴,这是全部的源代码:
package image;import java.io.ByteArrayInputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import javax.imageio.ImageIO;import javax.imageio.ImageReader;import javax.imageio.metadata.IIOMetadata;import javax.imageio.metadata.IIOMetadataNode;import org.w3c.dom.NamedNodeMap;import org.w3c.dom.Node;import org.w3c.dom.NodeList;import com.sun.imageio.plugins.png.PNGMetadata;public class pngTest {static private byte[] getContent(String filePath) throws IOException { File file = new File(filePath);long fileSize = file.length();if (fileSize > Integer.MAX_VALUE) { System.out.println("file too big...");return null; } FileInputStream fi = new FileInputStream(file);byte[] buffer = new byte[(int) fileSize];int offset = 0;int numRead = 0;while (offset < buffer.length && (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) { offset += numRead; }if (offset != buffer.length) { fi.close();throw new IOException("Could not completely read file "+ file.getName()); } fi.close();return buffer; }static private void readCustomData(byte[] imageData) throws IOException{ ImageReader imageReader = ImageIO.getImageReadersByFormatName("png").next(); imageReader.setInput(ImageIO.createImageInputStream(new ByteArrayInputStream(imageData)), true); IIOMetadata metadata = imageReader.getImageMetadata(0); PNGMetadata pngmeta = (PNGMetadata) metadata; printNode(pngmeta.getStandardChromaNode()); printNode(pngmeta.getStandardCompressionNode()); printNode(pngmeta.getStandardDataNode()); printNode(pngmeta.getStandardDimensionNode()); printNode(pngmeta.getStandardDocumentNode()); printNode(pngmeta.getStandardTextNode()); printNode(pngmeta.getStandardTransparencyNode()); }static private void printNode(IIOMetadataNode metanode){if (metanode == null)return; NodeList childNodes = metanode.getChildNodes();if( childNodes == null)return;for (int i = 0; i < childNodes.getLength(); i++) { Node node = childNodes.item(i); NamedNodeMap attribute = node.getAttributes();if( attribute == null)continue;int length = attribute.getLength();for( int j = 0; j < length; j++){ Node each = attribute.item(j); String value = each.getNodeValue(); String name = each.getNodeName(); System.out.println("Name: " + name + " value: " + value); } } }static public void main(String[] arg) throws IOException{byte[] content = getContent("C:\Users\i042416\Desktop\test\clipboard1.png"); readCustomData(content); } }
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