Re: [platform-swt-dev] Antialiased rendering on a transparent image

[Kirill Grouchnikov <kirillcool@xxxxxxxxx>]

Hi Felipe,

Thanks for the reply. Is it possible to create a fully transparent image and then draw text / line in anti-aliased mode on that image? Or are you saying that the OS will make all the text pixels fully opaque? If this is true, then does it mean that i have to paint the relevant background myself before drawing the text?

I was thinking about drawing the background separately and then draw the text as a translucent layer on top of that and have it "blended" together. This can be done in Swing's Java2D quite easily. But perhaps for AA rendering the "outlier" pixels derive their color from the underlying background, which would mean that you can't apply the same translucent text on any random background color.

Thanks
Kirill

----- Original Message ----
From: Felipe Heidrich <Felipe_Heidrich@xxxxxxxxxx>
To: Eclipse Platform SWT component developers list. <platform-swt-dev@xxxxxxxxxxx>
Sent: Friday, November 16, 2007 9:43:38 AM
Subject: Re: [platform-swt-dev] Antialiased rendering on a transparent image

Hi Kirill

Currently, the operating system will not set alpha in the image where the
text is drawn. The resulting pixel is text foreground composed with
background and alpha value of the antialiasing for that pixel.

Felipe





Kirill Grouchnikov <kirillcool@xxxxxxxxx>
Sent by: platform-swt-dev-bounces@xxxxxxxxxxx
15/11/2007 08:22 PM
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[platform-swt-dev] Antialiased rendering on a transparent image






After searching Google for relevant examples and posting on SWT forum and
getting no replies, i'm finally turning to the "source".

Is it possible to create a fully transparent SWT image and then render
antialiased text or other primitives (such as lines) on it? If i just mark
one color as transparent, it will not mark the anti-aliased pixels around
the text as having partial translucency - or perhaps this is an expected
result with subpixel rendering? Or perhaps the subpixel rendering expects
the background color / texture to be present in order to create the
correct blended text pixels?

What i'm looking for is to create an SWT image, render some text and then
iterate over the pixels of the SWT image, expecting alpha value to be 0
where there is no text, 255 where there is a full pixel and between 0 and
255 in the pixels around the text.

Hope this makes sense.

Thanks
Kirill


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