Data URI - how to create them in Java?
I have just been told to send the thumbnail of an image using data URI. I have been searching it but all I found was that its basically a textual representation of a file and can be directly used in HTML. I could not really find how to make a data URI in Java. I have an input stream of a file. Can someone please shed some light on it and point me to a way to generate this?
Answer
E.G. for an image:
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
ImageIO.write(image, "png", baos);
} catch (IOException e) {
e.printStackTrace();
}
String imageString = "data:image/png;base64," +
DatatypeConverter.printBase64Binary(baos.toByteArray());
Example
Run the code below. If FF is the default browser, you might see something like this:
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.xml.bind.DatatypeConverter;
public class DataUriConverter {
static String getImageAsString(BufferedImage image) throws Exception {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
// serialize the image
ImageIO.write(image, "png", baos);
// convert the written image to a byte[]
byte[] bytes = baos.toByteArray();
System.out.println("bytes.length " + bytes.length);
// THIS IS IT! Change the bytes to Base 64 Binary
String data = DatatypeConverter.printBase64Binary(bytes);
// add the 'data URI prefix' before returning the image as string
return "data:image/png;base64," + data;
}
static BufferedImage getImage() {
int sz = 500;
BufferedImage image = new BufferedImage(
sz, sz, BufferedImage.TYPE_INT_ARGB);
// paint the image..
Graphics2D g = image.createGraphics();
g.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g.setColor(new Color(0,0,255,63));
g.setStroke(new BasicStroke(1.5f));
for (int ii = 0; ii < sz; ii += 5) {
g.drawOval(ii, ii, sz - ii, sz - ii);
}
g.dispose();
return image;
}
public static void main(String[] args) throws Exception {
String imageString = getImageAsString(getImage());
String htmlFrag = "<html><body><img src='%1s'></body></html>";
String html = String.format(htmlFrag, imageString);
// write the HTML
File f = new File("image.html");
FileWriter fw = new FileWriter(f);
fw.write(html);
fw.flush();
fw.close();
// display the HTML
Desktop.getDesktop().open(f);
}
}