Date Time out of JPEG

Question

Hi,
I have taken some photos with my digital camera. When I hover over them in windows xp, a popup tells me exactly when the photo was taken. This must be stored as some meta-data within the jpeg image but I can't figure out how to get to that data using either the image i/o or JAI.
Can anyone help, please?
Thanks,
Dave

Answer 1

Here is code to dump out meta data:
import java.io.*;
import java.net.URL;
import java.util.*;
import javax.imageio.*;
import javax.imageio.metadata.*;
import javax.imageio.stream.*;
import org.w3c.dom.*;
public class Meta {
    public static void main(String[] args) throws IOException {
        String loc = "file:images/Camera.png";
        URL url = new URL(loc);
        InputStream stream = url.openStream();
        ImageInputStream in = ImageIO.createImageInputStream(stream);
        String suffix = loc.substring(loc.lastIndexOf('.')+1);
        Iterator readers = ImageIO.getImageReadersBySuffix(suffix);
        while (readers.hasNext()) {
            ImageReader reader = (ImageReader) readers.next();
            reader.setInput(in);
            IIOMetadata meta = reader.getImageMetadata(0);
            String[] formats = meta.getMetadataFormatNames();
            for(int i=0; i<formats.length; ++i)
                dump(meta.getAsTree(formats), 0);
static void dump(Node node, int spaces) {
indent(spaces);
System.out.print("<" + node.getNodeName());
if (node.hasAttributes()) {
NamedNodeMap map = node.getAttributes();
for(int i=0; i< map.getLength(); ++i) {
Node attr = map.item(i);
System.out.print(' '+ attr.getNodeName() + "=\"" + attr.getNodeValue()+"\"");
System.out.print('/');
System.out.println(">");
if (node.hasChildNodes()) {
for (Node child = node.getFirstChild(); child != null; child = child.getNextSibling())
dump(child, spaces+4);
indent(spaces);
System.out.println("</" + node.getNodeName() + '>');
static void indent(int spaces) {
for ( ; spaces>0; --spaces)
System.out.print(' ');
I ran it on a png file that was lying around on my machine and got the output:
<javax_imageio_png_1.0>
    <IHDR width="20" height="20" bitDepth="8" colorType="RGBAlpha" compressionMethod="deflate" filterMethod="adaptive" interlaceMethod="none"/>
    <bKGD>
        <bKGD_RGB red="255" green="255" blue="255"/>
    </bKGD>
    <gAMA value="45455"/>
    <pHYs pixelsPerUnitXAxis="2834" pixelsPerUnitYAxis="2834" unitSpecifier="meter"/>
    <tIME year="2000" month="11" day="30" hour="21" minute="32" second="56"/>
</javax_imageio_png_1>
<javax_imageio_1.0>
    <Chroma>
        <ColorSpaceType name="RGB"/>
        <NumChannels value="4"/>
        <Gamma value="0.45455"/>
        <BlackIsZero value="true"/>
        <BackgroundColor red="255" green="255" blue="255"/>
    </Chroma>
    <Compression>
        <CompressionTypeName value="deflate"/>
        <Lossless value="true"/>
        <NumProgressiveScans value="1"/>
    </Compression>
    <Data>
        <PlanarConfiguration value="PixelInterleaved"/>
        <SampleFormat value="UnsignedIntegral"/>
        <BitsPerSample value="8 8 8 8"/>
    </Data>
    <Dimension>
        <PixelAspectRatio value="1.0"/>
        <ImageOrientation value="Normal"/>
        <HorizontalPixelSize value="0.35285816"/>
        <VerticalPixelSize value="0.35285816"/>
    </Dimension>
    <Document>
        <ImageModificationTime year="2000" month="11" day="30" hour="21" minute="32" second="56"/>
    </Document>
    <Transparency>
        <Alpha value="nonpremultipled"/>
    </Transparency>
</javax_imageio_1>But I haven't found time data stored in any jpeg I tried. Perhaps the app is simply using the image file's lastModified attribute if it can't find information inside the file?