Better GrayscaleDecorator
-------------------------
Key: PIVOT-723
URL: https://issues.apache.org/jira/browse/PIVOT-723
Project: Pivot
Issue Type: Improvement
Components: wtk-effects
Affects Versions: 2.0
Reporter: Bill van Melle
Priority: Minor
The current GrayscaleDecorator doesn't work properly when the decorated
component uses transparency -- it turns the transparent pixels black, which
seems unlikely to be what you want. Here's a new version of
GrayscaleDecorator#prepare that creates the BufferedImage in a
transparency-aware way:
public Graphics2D prepare(Component component, Graphics2D graphics) {
this.graphics = graphics;
int width = component.getWidth();
int height = component.getHeight();
// To convert to gray, we create a BufferedImage in the grayscale color
space
// into which the decorated component draws, and we output the
resulting image.
// The naive way to create the buffer is
// new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
// but that doesn't respect transparency. Hence the following more
complicated method.
if (bufferedImage == null
|| bufferedImage.getWidth() < width
|| bufferedImage.getHeight() < height) {
ColorSpace gsColorSpace =
ColorSpace.getInstance(ColorSpace.CS_GRAY);
ComponentColorModel ccm = new ComponentColorModel(gsColorSpace,
true, false,
Transparency.TRANSLUCENT, DataBuffer.TYPE_BYTE);
WritableRaster raster = ccm.createCompatibleWritableRaster(width,
height);
bufferedImage = new BufferedImage(ccm, raster,
ccm.isAlphaPremultiplied(), null);
}
bufferedImageGraphics = bufferedImage.createGraphics();
bufferedImageGraphics.setClip(graphics.getClip());
return bufferedImageGraphics;
}
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