Previous | Next | Trail Map | Creating a User Interface | Working with Graphics


Displaying Images

Here is a code example that displays an image at its normal size in the upper left corner of the Component area (0, 0):
g.drawImage(image, 0, 0, this);
Here is a code example that displays an image scaled to be 400 pixels wide and 68 pixels tall, starting at the coordinates (125, 0):
g.drawImage(myImage, 125, 0, 400, 68, this);
Below is an applet that loads a single image and displays it twice, using both code examples that you see above. Here is the full code for the program (which can function both as an applet and as an application).


Your applet browser doesn't understand the <APPLET> tag. Here's what you'd see if it did:


The Graphics class declares the following drawImage() methods. They all return a boolean value, although this value is rarely used. The return value is true if the image has been completely loaded [and thus completely drawn?]; otherwise, it's false [CHECK].

The drawImage() methods have the following arguments:
Image img
The image to draw.
int x, int y
The coordinates of the upper left corner of the image.
int width, int height
The width and height (in pixels) of the image.
Color bgcolor
The color to draw underneath the image. This can be useful if the image contains transparent pixels.
ImageObserver observer
An object that implements the ImageObserver interface. This object will be notified whenever new information about the image becomes available. Most programs can simply specify this.
The reason why this works as the image observer is that the Component class implements the ImageObserver interface. Its implementation invokes the repaint() method as the image data is loaded, which is usually what you want to happen.

The drawImage() returns immediately [after displaying the image?], even if the image data hasn't been fully loaded (and thus might be displayed only partially). If you want to make sure that drawImage() draws only complete images, then you must track image loading. As the previous page explains, you can track image loading either by implementing ImageObserver in your Component or by using the MediaTracker class. An example of using MediaTracker is in Improving the Appearance and Performance of Image Animation.


Previous | Next | Trail Map | Creating a User Interface | Working with Graphics