Subtracting from rect.Top

[toe_head2001]

I'm try to get a my (smaller) 'img' Surface lined up with the selection of the canvas.

 

Say I have a selection start at point (50,50), and run this code:

...

img = Surface.CopyFromBitmap(myBitmap);

void Render(Surface dst, Surface src, Rectangle rect)
{
    for (int y = rect.Top; y < rect.Bottom; y++)
    {
        for (int x = rect.Left; x < rect.Right; x++)
        {
            dst[x,y] = img.GetBilinearSample(x - rect.Left,y - rect.Top);
        }
    }

Substracting from 'rect.Left' on 'x' makes it start from 0 as expected, but subtracting from 'rect.Top' on y doesn't seem to work.

 

Can you explain why that is?

[midora]

Missing the check for width and height of the small img surface. Maybe use the clamped variant of GetBilinearSample.

[MJW]

rect is the ROI, not the selection. It works for X because for rectangular selections, the X origins of the ROIs coincide with the X origin of the selection.

 

Get the selection (as done in CodeLab) by: Rectangle selection = EnvironmentParameters.GetSelection(src.Bounds).GetBoundsInt();

Then: dst[x,y] = img.GetBilinearSample(x - selection.Left,y - selection.Top);

Edited August 23, 2015 by MJW

[toe_head2001]

rect is the ROI, not the selection. It works for X because for rectangular selections, the X origins of the ROIs coincide with the X origin of the selection.

 

Thanks for explaining this!

 

This whole time I thought the ROI was based on the selection. I never bothered reading that part of the code to understand what was going on.

[Rick Brewster]

The ROI is based on the selection. But each rectangle describes only a part of the ROI.

[TechnoRobbo]

this may gave you some insight - run this, don't even build it , just paste it in CodeLab. Then try a selection.

// Name:
// Submenu:
// Author:
// Title:
// Desc:
// Keywords:
// URL:
// Help:
#region UICode
#endregion


Random rndm = new Random((int)Guid.NewGuid().GetHashCode());
void Render(Surface dst, Surface src, Rectangle rect)
{

    ColorBgra CurrentPixel = ColorBgra.FromBgr( (byte)rndm.Next(256),
        (byte)rndm.Next(256),(byte)rndm.Next(256));
    for (int y = rect.Top; y < rect.Bottom; y++)
    {
        if (IsCancelRequested) return;
        for (int x = rect.Left; x < rect.Right; x++)
        {
            dst[x,y] = CurrentPixel;
        }
    }
}

[BoltBait]

Or, you could just read this page:

http://boltbait.com/pdn/CodeLab/help/overview.asp

[toe_head2001]

Or, you could just read this page:

http://boltbait.com/pdn/CodeLab/help/overview.asp

 

Indeed, it's been much to long since I read that, and apparently I didn't fully understand it that first time.

 

Thanks everyone.