org.freedesktop.cairo
Class Operator

Object
  org.freedesktop.bindings.Constant
      org.freedesktop.cairo.Operator

public class Operator
extends org.freedesktop.bindings.Constant

Constants specifying the compositing operating mode in effect. These are set for a drawing Context using setOperator(), and take effect when commands like paint() are invoked.

The Context should be created using a cairo Surface. The operators don't seem to work correctly when a Drawable is used instead of a cairo Surface.

The example images shown below were generated with the following code:

 cr.rectangle(0, 0, 75, 75);
 cr.setSource(0.7, 0, 0, 0.8);
 cr.fill();
 
 cr.setOperator(Operator.FOO);
 
 cr.rectangle(40, 40, 75, 75);
 cr.setSource(0, 0, 0.9, 0.4);
 cr.fill();
 

The drawing operations in cairo are said to be bounded and unbounded with reguards to the Surface to be drawn to.

When an operator is said to be bounded any cairo mask present determines where the operation is applied.

When an operator is said to be unbounded the operation is applied ignoring any present mask. Note: Clipping can still limit an unbounded operator.

Since:

4.0.7

Author:

Andrew Cowie, Kenneth Prugh, Zak Fenton

ADD

public static final Operator ADD

Add the colors of the overlapping region.

This operator has the same effect for bounded and unbounded.

Since:

4.0.16

ATOP

public static final Operator ATOP

Draw only where existing pixels are, mixing the color of the overlapping region.

This operator has the same effect for bounded and unbounded.

Since:

4.0.16

CLEAR

public static final Operator CLEAR

Clear a surface to all transparent.

This operator is bounded.

Since:

4.0.7

DEST

public static final Operator DEST

Any existing pixels are left untouched, while the current drawing is discarded.

This operator has the same effect for bounded and unbounded.

Since:

4.0.16

DEST_ATOP

public static final Operator DEST_ATOP

Draw and clear any existing pixels outside the overlapping region, the color of the overlapping region is mixed similar to the ATOP Operator.

This operator is unbounded.

Since:

4.0.16

DEST_IN

public static final Operator DEST_IN

Draw below the overlapping region, clearing everything outside the region similar to the IN Operator.

This operator is unbounded.

Since:

4.0.16

DEST_OUT

public static final Operator DEST_OUT

Reduce the visibility of the overlapping region.

This operator has the same effect for bounded and unbounded.

Since:

4.0.16

DEST_OVER

public static final Operator DEST_OVER

Draw below any existing pixels with similar results to the OVER operator.

This operator has the same effect for bounded and unbounded.

Since:

4.0.16

IN

public static final Operator IN

Draw only where existing pixels are, clearing the rest of the surface.

This operator is unbounded.

Since:

4.0.16

OUT

public static final Operator OUT

Draw only where existing pixels are not present, leaving a shadow behind where the two overlapped due to transparency.

This operator is unbounded.

Since:

4.0.16

OVER

public static final Operator OVER

Draws the specified source object over the underlying object as if both objects were two overlapping panels of transparent glass. This only applies to objects that have an alpha channel; if the objects do not have an alpha channel, the source object simply paints over the underlying object.

This is the default operator.

This operator has the same effect for bounded and unbounded.

Since:

4.0.10

SATURATE

public static final Operator SATURATE

Saturate the colors of the overlapping region.

This operator has the same effect for bounded and unbounded.

Since:

4.0.16

SOURCE

public static final Operator SOURCE

Draw over existing pixels as if they were not present.

This operator is bounded.

As an example, you could set up the object to be drawn over:

 cr.setSource(0.7, 0, 0, 0.8);
 cr.rectangle(15, 10, 50, 50);
 cr.fill();
 

Now set up the source object that will draw over the area beneath it:

 cr.setSource(0, 0, 0.9, 0.4);
 cr.rectangle(35, 35, 50, 50);
 cr.setOperator(Operator.SOURCE);
 cr.fill();
 

Since:

4.0.16

XOR

public static final Operator XOR

XOR the colors of the overlapping region.

This operator has the same effect for bounded and unbounded.

Since:

4.0.16

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