Matrix (java-gnome 4.0.19 API Documentation)

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java-gnome version 4.0.19

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org.freedesktop.cairo
Class Matrix

Object
  org.freedesktop.bindings.Pointer
      org.freedesktop.bindings.Proxy
          org.freedesktop.cairo.Matrix

public class Matrix
extends org.freedesktop.bindings.Proxy
extends org.freedesktop.bindings.Proxy

A matrix describing an affine transformation.

You can apply this transformation to a Cairo Context with its transform() method as follows:

 matrix = new Matrix();
 matrix.rotate(...);    // and/or
 matrix.scale(...);     // and/or
 matrix.translate(...); 
 
 cr.transform(matrix);

Calls to the rotate(), scale(), and translate methods are cumulative on a given Matrix.

Applying a transformation is what take you from device co-ordinates to user-space co-ordinates; you are in fact always working in the later but we tend not to focus on this as the default is naturally no transformation.

Examples

In each of the illustrations below, we draw a box as follows:

 cr.setSource(0.7, 0.8, 0.8);
 cr.rectangle(5, 5, 25, 15);
 cr.stroke();

We then apply the transform shown, change colour to blue, and then draw the exact same rectangle again:

 cr.setSource(0.0, 0.0, 1.0);
 cr.rectangle(5, 5, 25, 15);
 cr.stroke();

Thus both the original rectangle and the result of the matrix operation are shown.

Since:: 4.0.10
Author:: Andrew Cowie

Constructor Summary
`Matrix()` Construct a new transformation matrix with the identity (no-op) transform.

Method Summary
`void`	`rotate(double angle)` Rotate the transformation by the given angle.
`void`	`scale(double sx, double sy)` Scale by `sx` horizontally and `sy` vertically.
`void`	`translate(double tx, double ty)` Translate by `tx` horizontally and `ty` vertically.

Methods inherited from class org.freedesktop.bindings.Pointer
`toString`

Methods inherited from class Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

Matrix

public Matrix()

Construct a new transformation matrix with the identity (no-op) transform.

Since:: 4.0.10

Method Detail

rotate

public void rotate(double angle)

Rotate the transformation by the given angle. As with elsewhere in Cairo, angle is in radians.

 matrix.rotate(-Math.PI / 4.0);
 cr.transform(matrix);

A negative angle is used in this example for the same reason as discussed in arc().

Since:: 4.0.10

scale

public void scale(double sx,
                  double sy)

Scale by sx horizontally and sy vertically.

 matrix.scale(-0.8, 1.6);
 cr.transform(matrix);

Note that in this example the sx argument being negative results in a reflection through the y axis. Note also that the line widths are not the same as the original image's were; only scaling by 1.0 would have left the widths alone.

Don't scale by 0.

Since:: 4.0.10

translate

public void translate(double tx,
                      double ty)

Translate by tx horizontally and ty vertically.

 matrix.translate(5, 10);
 cr.transform(matrix);

Since:: 4.0.10