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https://issues.apache.org/jira/browse/PIVOT-723?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Bill van Melle updated PIVOT-723:
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Attachment: error-round.png
Sample png with transparency to demonstrate the issue. Taken from the
Wikimedia commons page http://commons.wikimedia.org/wiki/Tango_icon where there
are lots more examples.
> 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
> Attachments: error-round.png
>
>
> 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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