Something like this works for me.
On the server:
import java.awt.Container;
import java.awt.Graphics2D;
import java.awt.MediaTracker;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ImageServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse
response) {
double thumbWidth;
double thumbHeight;
String imagefile = request.getParameter("file");
String height = request.getParameter("h");
String width = request.getParameter("w");
// System.err.println(imagefile + ", " + height + ", " + width);
// Set the mime type of the image
response.setContentType("image/png");
try {
java.awt.Image image =
Toolkit.getDefaultToolkit().getImage
(imagefile);
MediaTracker mediaTracker = new MediaTracker(new
Container());
mediaTracker.addImage(image, 0);
mediaTracker.waitForID(0);
int imageWidth = image.getWidth(null);
int imageHeight = image.getHeight(null);
double imageRatio = (double) imageWidth / (double)
imageHeight;
// if width parameter is null, then just use it to scale
thumbHeight = new Double(height);
if (width != null) {
thumbWidth = new Double(width);
// determine size from WIDTH and HEIGHT
double thumbRatio = thumbWidth / thumbHeight;
if (thumbRatio < imageRatio) {
thumbHeight = thumbWidth / imageRatio;
} else {
thumbWidth = thumbHeight * imageRatio;
}
} else {
thumbWidth = thumbHeight * imageRatio;
}
// draw original image to thumbnail image object and
scale it to
the new size on-the-fly
BufferedImage thumbImage = new BufferedImage((int)
thumbWidth,
(int) thumbHeight, BufferedImage.TYPE_INT_RGB);
Graphics2D graphics2D = thumbImage.createGraphics();
graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
graphics2D.drawImage(image, 0, 0, (int) thumbWidth,
(int)
thumbHeight, null);
graphics2D.dispose();
ImageIO.write(thumbImage, "png",
response.getOutputStream());
} catch (Exception e) {
e.printStackTrace();
}
}
}
On the client, create a URL to get the image something like this:
StringBuffer sb = new StringBuffer(GWT.getHostPageBaseURL());
sb.append("ImageServlet?file=");
sb.append(imagefilel);
sb.append("&h=" + Utils.getPageHeight());
sb.append("&w=" + Utils.getPageWidth());
Image image = new Image(sb.toString);
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