Is current pixel selected?

[BoltBait]

When running the following loop (from codelab):

void Render(Surface dst, Surface src, Rectangle rect)
{
   for(int y = rect.Top; y     {
       for (int x = rect.Left; x         {
       }
   }
}

How can I know if the current pixel (src[x, y] or dst[x, y]) is inside of the current selection?

With rectanglar selections, it seems easy, but when you are working with a selection created with the circle, lasso or magic wand...

Thanks!

[Rick Brewster]

I think this should work ...

PdnRegion selectionRegion = this.EnvironmentParameters.GetSelection(src.Bounds);

if (selectionRegion.IsVisible(x, y))
{
   .... 
}

Note that if there is no selection, then selectionRegion will encompass the entire canvas area.

[Rick Brewster]

Actually ...

... x and y will always be inside the current selection.

Because effect rendering is always clipped to the current selection.

So, what are you trying to do?

[BoltBait]

Basically, I would like to write some type of feathering filter. I need to find the 'edges' of the selection so I can fiddle with the alpha of those pixels.

Let's say I have a given pixel that I'm looking at. If any of the 8 surrounding pixels are 'outside' of the current selection and this pixel is 'inside', then I have found an edge pixel and need to change the alpha of that pixel.

When working with areas selected with the magic wand, the selection can become quite complex.

[Rick Brewster]

Hrmm, I'm not so sure that'll work very well from an Effect without a dual quad core 3ghz Opteron (heh if only :twisted:). It only has access to the selection Region, not the original Path (PdnGraphicsPath).

[Illnab1024]

See, that's what I was thinking, although...

Yeah, you're technically working with 8x the original memory (or maybe nine...) and that's w/ 1 px feather...

[BoltBait]

Hrmm, I'm not so sure that'll work very well from an Effect without a dual quad core 3ghz Opteron (heh if only :twisted:). It only has access to the selection Region, not the original Path (PdnGraphicsPath).

Seeing how I work for Intel, there's no need to be rude.

I'm sure I could get my hands on a Quad Core if I really needed it.

Well, I was thinking that you draw those marching ants fairly quickly, why can't I get access to that path and modify the alpha of the edge pixels just as quickly?

But, even if I can't do it quickly, I would still like to do it slowly. So, is it possible?

BTW, I think you could do it by only checking a maximum of 4 directions instead of 8. Is that better?

[Rick Brewster]

I don't know man. The effects API just doesn't have access to the Path in 2.xx.