Help with Antialiasing a circle with GDI+

[LordAdef]

Hi guys,
I glued this example a bit in a hurry, but it works at least. Built with UASM. Attached the zip file with source code and .exe

In short, this is a way to use anti aliasing without GDI+. Purely with GDI.
The .exe file in the zip is using an upscale factor of 4. Meaning... how much 'bigger' we are drawing the thing in the back buffer. 

If interested, all the fun happens in the upscale_draw procedure.

GDI tends to be faster than GDI+. But I didn't benchmark comparing the two systems (mine, and Zedd's).


The left circle is in pure GDI. On the right, the same circle with the process applied:

[zedd151]

That looks pretty good. 

No worries about the timing. Where I would use it the speed limiting factor are mostly the users mouse clicks. Unless it will be used for a fast paced game. Then the time it takes could be critical to game performance.

[NoCforMe]

So it appears that you're really not processing the image at all, apart from scaling it up and back down again, amiright? I mean, you're not applying Bresenham's algorithm or anything like that.

Looks like all the magic happens here

Code Select Expand

    inv SetStretchBltMode, dc, HALFTONE
due to the HALFTONE parameter.

Pretty slick.

[LordAdef]

So it appears that you're really not processing the image at all, apart from scaling it up and back down again, amiright? I mean, you're not applying Bresenham's algorithm or anything like that.

Looks like all the magic happens here

Code Select Expand

    inv SetStretchBltMode, dc, HALFTONE
due to the HALFTONE parameter.

Pretty slick.

Yep,

Print the shape upscaled in the back buffer, than print it to your main dc. No processing.

[zedd151]

So it appears that you're really not processing the image at all

I'd call it minimal processing, since it does do more than nothing.

Pretty slick.

Yes, and very good results. I would have to compare several different image sizes between gdi and gdiplus to make a better determination of how good the results are. But so far, looks really good.

[LordAdef]

No worries about the timing. 

It's masm land after all, we want 'fast'

[LordAdef]

Zedd, I've been doing this for quite a while. But for shapes. 
Two things to bare in mind:

1. line thickness expands inward and outwards, and must be scaled. We need to calculate the offset of this expansion outwards, or it may hit the rect boundary.

2. the Drawback: for larger shapes, you need a larger back buffer. I am currently using it to create buttons

[zedd151]

Ok. brb I gotta go...

[jj2007]

all the fun happens in the upscale_draw procedure

The docs say you should add this:

Code Select Expand

    inv SetStretchBltMode, dc, HALFTONE  ;-> downsize back to original anti-aliasing
    inv SetBrushOrgEx, dc, 800, 800, 0
However, I can't see any difference. Well done, Alex

[LordAdef]

all the fun happens in the upscale_draw procedure

The docs say you should add this:

Code Select Expand

    inv SetStretchBltMode, dc, HALFTONE  ;-> downsize back to original anti-aliasing
    inv SetBrushOrgEx, dc, 800, 800, 0
However, I can't see any difference. Well done, Alex

Thanks Johen!
    inv SetBrushOrgEx, dc, 800, 800, 0

No clue... not broken..didn't fixed it

I am very curious to time both systems and see whats happening

[LordAdef]

Hi guys,

I've created a new thread in the Laboratory (since is timing related), where I compare the 2 system.
thread is here: https://masm32.com/board/index.php?topic=12708.0