Displaying images and thumbnails directly from database

[Chris Boldon]

I couldn't find many good examples on displaying images directly from the database (especially related to resizing), so I figured I'd post some code snips here to save people in the future some time:

ImageTools.java

public class ImageTools {
private static final Logger LOG = Logger.getLogger(ImageTools.class);
 
public Image createThumbnail(Image image) {
BufferedImage bufferedImage = toBufferedImage(image);
BufferedImage bufThumb = createThumbnail(bufferedImage);
Image thumbImage = toImage(bufThumb);
 
return thumbImage;
}
 
private static BufferedImage toBufferedImage(Image image) {
if (image instanceof BufferedImage) {
return (BufferedImage) image;
}
 
// This code ensures that all the pixels in the image are loaded
image = new ImageIcon(image).getImage();
 
// Determine if the image has transparent pixels; for this method's
// implementation, see e661 Determining If an Image Has Transparent
// Pixels
boolean hasAlpha = hasAlpha(image);
 
// Create a buffered image with a format that's compatible with the
// screen
BufferedImage bimage = null;
GraphicsEnvironment ge = GraphicsEnvironment
.getLocalGraphicsEnvironment();
try {
// Determine the type of transparency of the new buffered image
int transparency = Transparency.OPAQUE;
if (hasAlpha) {
transparency = Transparency.BITMASK;
}
 
// Create the buffered image
GraphicsDevice gs = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gs.getDefaultConfiguration();
bimage = gc.createCompatibleImage(image.getWidth(null), image
.getHeight(null), transparency);
} catch (HeadlessException e) {
LOG.error("This system does not have a screen", e);
}
 
if (bimage == null) {
// Create a buffered image using the default color model
int type = BufferedImage.TYPE_INT_RGB;
if (hasAlpha) {
type = BufferedImage.TYPE_INT_ARGB;
}
bimage = new BufferedImage(image.getWidth(null), image
.getHeight(null), type);
}
 
// Copy image to buffered image
Graphics g = bimage.createGraphics();
 
// Paint the image onto the buffered image
g.drawImage(image, 0, 0, null);
g.dispose();
 
return bimage;
}
 
private static boolean hasAlpha(Image image) {
// If buffered image, the color model is readily available
if (image instanceof BufferedImage) {
BufferedImage bimage = (BufferedImage) image;
return bimage.getColorModel().hasAlpha();
}
 
// Use a pixel grabber to retrieve the image's color model;
// grabbing a single pixel is usually sufficient
PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);
try {
pg.grabPixels();
} catch (InterruptedException e) {
LOG.error(e);
}
 
// Get the image's color model
ColorModel cm = pg.getColorModel();
return cm.hasAlpha();
}
 
private Image toImage(BufferedImage bufferedImage) {
return Toolkit.getDefaultToolkit().createImage(
bufferedImage.getSource());
}
 
private BufferedImage createThumbnail(BufferedImage orig) {
final int WIDTH = 75;
final int HEIGHT = 75;
AffineTransform at;
 
BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = image.createGraphics();
// g2.setPaint(bgColor);
g2.fillRect(0, 0, WIDTH, HEIGHT);
// scale to fit
double xScale = (double) WIDTH / orig.getWidth();
double yScale = (double) HEIGHT / orig.getHeight();
double scale = Math.min(xScale, yScale);
// center thumbnail image
double x = (WIDTH - orig.getWidth() * scale) / 2;
double y = (HEIGHT - orig.getHeight() * scale) / 2;
at = AffineTransform.getTranslateInstance(x, y);
at.scale(scale, scale);
g2.drawRenderedImage(orig, at);
g2.dispose();
 
return image;
}
}

DisplayImageAction.java:

public class DisplayImageAction extends Action {
private static final Logger LOG = Logger
.getLogger(DisplayImageAction.class);
 
private ListerFacade listerFacade;
 
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
 
LOG.debug("Creating image from Blob");
String listingId = request.getParameter("listing");
Blob imgBlob = listerFacade.getListingById(Integer.valueOf(listingId))
.getFile().getFileBin();
try {
byte[] picBytes = imgBlob.getBytes(1, (int) imgBlob.length());
response.setContentType("image/jpeg");
response.getOutputStream().write(picBytes);
} catch (SQLException e) {
LOG.error(e);
} catch (IOException e) {
LOG.error(e);
}
 
return null;
}

DisplayThumbnailAction:

public class DisplayThumbnailAction extends Action {
private static final Logger LOG = Logger
.getLogger(DisplayThumbnailAction.class);
 
ImageTools imageTools = new ImageTools();
 
private ListerFacade listerFacade;
 
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
 
LOG.debug("Creating thumbnail from Blob");
String listingId = request.getParameter("listing");
Blob imgBlob = listerFacade.getListingById(Integer.valueOf(listingId))
.getFile().getFileBin();
 
try {
byte[] picBytes = imgBlob.getBytes(1, (int) imgBlob.length());
Image image = Toolkit.getDefaultToolkit().createImage(picBytes);
 
Image thumbImage = imageTools.createThumbnail(image);
byte[] thumbBytes = imageToByteArray(thumbImage);
 
response.setContentType("image/jpeg");
response.getOutputStream().write(thumbBytes);
 
} catch (SQLException e) {
LOG.error(e);
} catch (IOException e) {
LOG.error(e);
}
 
return null;
}
 
public static byte[] imageToByteArray(Image image) {
 
try {
MediaTracker tracker = new MediaTracker(new Container());
tracker.addImage(image, 0);
try {
tracker.waitForAll();
} catch (InterruptedException e) {
}
BufferedImage bufferedImage = new BufferedImage(image
.getWidth(null), image.getHeight(null), 1);
Graphics gc = bufferedImage.createGraphics();
gc.drawImage(image, 0, 0, null);
 
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ImageIO.write(bufferedImage, "jpeg", bos);
 
return bos.toByteArray();
} catch (IOException e) {
LOG.error(e);
}
return null;
}
}

[Brent Sterling]

Thanks for posting...could be useful. Does this code use just standard Java libraries for the image manipulation?

- Brent

[Chris Boldon]

Yes, it is standard java libraries.