Start of Tutorial > Start of Trail > Start of Lesson |
Search
Feedback Form |
You can modify the transform attribute in theGraphics2D
context to move, rotate, scale, and shear graphics primitives when they are rendered. The transform attribute is defined by an instance ofAffineTransform
. (An affine transform is a transformation such as translate, rotate, scale, or shear in which parallel lines remain parallel even after being transformed.)
Graphics2D
provides several methods for changing the transform attribute. You can construct a newAffineTransform
and change theGraphics2D
transform attribute by callingsetTransform
.
AffineTransform
defines the following factory methods to make it easier to construct new transforms:
getRotateInstance
getScaleInstance
getShearInstance
getTranslateInstance
Alternatively you can use one of the
Graphics2D
transformation methods to modify the current transform. When you call one of these convenience methods, the resulting transform is concatenated with the current transform and is applied during rendering:
rotate
--to specify an angle of rotation in radiansscale
--to specify a scaling factor in the x and y directionsshear
--to specify a shearing factor in the x and y directionstranslate
--to specify a translation offset in the x and y directionsYou can also construct an
AffineTransform
directly and concatenate it with the current transform by calling thetransform
method.The
drawImage
method is also overloaded to allow you to specify anAffineTransform
that is applied to the image as it is rendered. Specifying a transform when you calldrawImage
does not affect theGraphics2D
transform attribute.
The following program is the same asStrokeandFill
, but also allows the user to choose a transformation to apply to the selected object when it is rendered.
This is a picture of the applet's GUI. To run the applet, click the picture. The applet will appear in a new browser window.
Transform.java
contains the complete code for this applet.When a transform option is chosen, an instance of
AffineTransform
at is modified and is then concatenated with a translation transform that moves theShape
to the center of the window. The resulting transform is then passed to thesetTransform
method to set theGraphics2D
transform attribute.switch (Transform.trans.getSelectedIndex()){ case 0 : at.setToIdentity(); at.translate(w/2, h/2); break; case 1 : at.rotate(Math.toRadians(45)); break; case 2 : at.scale(0.5, 0.5); break; case 3 : at.shear(0.5, 0.0); break; ... AffineTransform toCenterAt = new AffineTransform(); toCenterAt.concatenate(at); toCenterAt.translate(-(r.width/2), -(r.height/2)); g2.setTransform(toCenterAt);
Start of Tutorial > Start of Trail > Start of Lesson |
Search
Feedback Form |