Class GroupGraphics

java.lang.Object
java.awt.Graphics
java.awt.Graphics2D
org.apache.pdfbox.rendering.GroupGraphics

class GroupGraphics extends Graphics2D
Graphics implementation for non-isolated transparency groups.

Non-isolated groups require that the group backdrop (copied from parent group or page) is used as the initial contents of the image to which the group is rendered. This allows blend modes to blend the group contents with the graphics behind the group. Finally when the group rendering is done, backdrop removal must be computed (see removeBackdrop). It ensures the backdrop is not rendered twice on the parent but it leaves the effects of blend modes.

This class renders the group contents to two images. groupImage is initialized with the backdrop and group contents are drawn over it. groupAlphaImage is initially fully transparent and it accumulates the total alpha of the group contents excluding backdrop.

If a non-isolated group uses only the blend mode Normal, it can be optimized and rendered like an isolated group; backdrop usage and removal are not needed.