Eclipse Community Forums: Remote Application Platform (RAP) » Alpha of ImageData not working for RAP

Home » Eclipse Projects » Remote Application Platform (RAP) » Alpha of ImageData not working for RAP(Setting ImageData.alpha has no effect in RAP)

Alpha of ImageData not working for RAP [message #1404771]

Tue, 05 August 2014 11:35

Eclipse User

Alpha transparency for SWT ImageData does not appear to be supported by RAP.
In SWT I often used this to create a series of images with different alpha values in order to animate a fade-out or fade-in effect, but this has no effect in RAP (or Tabris in fact), and the image remains at 100% alpha.

My code is something like this:

Image alphaImage = ...;
ImageData alphaImageData = alphaImage.getImageData();
alphaImageData.alpha = desiredAlpha; // 0-255
Image adjustedAlphaImage = new Image(display, alphaImageData);
myLabel.setImage(adjustedAlphaImage);

Is this a known limitation of RAP, or is it a bug?

Thanks, John

Re: Alpha of ImageData not working for RAP [message #1404931 is a reply to message #1404771]

Wed, 06 August 2014 03:14

Eclipse User

Hi John,
RAP is using SWT org.eclipse.swt.graphics.ImageLoader#save to make an
image file from image data. Could you try the same code in SWT, but
instead setting the image on the Label directly, save it to a file
(with ImageLoader). Is the output image transparent? See also:
438401: Image created from ImageData does not show up on a label
https://bugs.eclipse.org/bugs/show_bug.cgi?id=438401

Best,
Ivan

--
Ivan Furnadjiev

Twitter: @EclipseRAP
Blog: http://eclipsesource.com/blogs/

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Re: Alpha of ImageData not working for RAP [message #1404950 is a reply to message #1404931]

Wed, 06 August 2014 04:08

Eclipse User

That pointed me in the right direction...
PNG images are not saved with the alpha value for the overall image... only the alphaBytes[] array. Therefore, I've changed my logic to set the alphaBytes[] and don't touch alpha at all, and this works perfectly in RAP.
Thanks Ivan!
John

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