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Anti-aliasing canvas graphics

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Jeff Gonis

Anti-aliasing canvas graphics

Hopefully this isn't double posted, I sent it in yesterday, but I wasn't a list member and it was pending approval. I figured I should join the list anyway, so without further ado here is my question.

---------- Forwarded message ----------
From: Jeff Gonis <[hidden email]>
Date: Mon, Dec 21, 2009 at 5:20 PM
Subject: Anti-aliasing canvas graphics
To: [hidden email]

Hi everyone,

I am executing the following code in the drawOn: method of a morph I am experimenting with as a canvas for some possible turtle graphics experiments:
super drawOn: aCanvas.
    (aCanvas respondsTo: #asBalloonCanvas)
        ifTrue: [| bc |
            bc := aCanvas asBalloonCanvas.
            bc aaLevel: 4.
            bc
                line: (self bounds topLeft translateBy: 3 @ 3)
                to: (self bounds bottomRight translateBy: -4 @ -4)
                width: 3
                color: Color red]

This gives me the look I want, except for the fact that the line isn't really anti-aliased. I have attached a screen shot of what the line looks like in the morph. I am wondering how I can go about getting a better looking line with less noticeable aliasing when I draw.

Thanks for your help,
Jeff G.

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canvasExample.JPG (37K) Download Attachment

Andreas.Raab

Re: Anti-aliasing canvas graphics

Jeff Gonis wrote:
> This gives me the look I want, except for the fact that the line isn't
> really anti-aliased. I have attached a screen shot of what the line
> looks like in the morph. I am wondering how I can go about getting a
> better looking line with less noticeable aliasing when I draw.

There is an optimization in BalloonCanvas trying to use the faster
FormCanvas and you're running afoul of it. Try this instead:

bc
drawPolygon: {startPt. endPt}
color: nil
borderWidth: 3
borderColor: Color red

Cheers,
- Andreas
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Jeff Gonis

Re: Re: Anti-aliasing canvas graphics

Andreas,

Thanks for the help. For some reason I was still in non-squeak mode where I was thinking that I would need to rely on getting the help of experts instead of, *duh*, reading the code myself! I read the code for BalloonCanvas and looked at the old WatchMorph in an earlier version of squeak and I found the optimization and work around you mentioned. It takes some time to get used to have all the source available I guess!

Thanks for your help,
Jeff G.

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