Get the bounding rectangle of multiple rectangles

3
votes

I have up to 4 rectangles on an image, for each of these rectangles I know their top left X,Y coordinate and their width,height. I want to create an Int32Rect with dimensions from most top left rectangle to the most bottom right rectangle. The main issue is that you can only create a System.Windows.Int32Rect with x,y,width,height parameters. Any ideas how I can accomplish this with my currently known values?

EDIT: Trying to clarify, I want to create a Int32Rect that is the dimensions of all other "rectangles" on my image. So one large Int32Rect that starts from the "rectangle" at the top-left portion of the image and stretches to the "rectangle" that is at the bottom-right portion of the image.

Here's some code that does this for a single rectangle:

var topLeftOfBox = new Point(centerOfBoxRelativeToImage.X - Box.Width/2,
                centerOfBoxRelativeToImage.Y - Box.Height/2);
return new CroppedBitmap(originalBitmap, new Int32Rect(topLeftOfBox.X, topLeftOfBox.Y, Box.Width, Box.Height));

Thanks for the help and ideas everyone, I found Aybe's answer to work the best for me.

3
c#rectangles
You say you have the top, left, X, Y and the width and height. I don't see the problem because you could just pass the X, Y, Width, and Height parameters to the Int32Rect. - Aaron Hawkins
This seems to be a rather trivial min/max calculation. Can you post your best try and a problem description? - nvoigt
@AaronHawkins I can do this for a single rectangle but I want to do this for multiple Rectangles. - invizion
@nvoigt see update to question, see if that helps - invizion

3 Answers

3
votes

You need to grab x/y mins/maxs for each rectangle and build a rectangle out of these values:

using System.Linq;
using System.Windows;

internal class Class1
{
    public Class1()
    {
        var rect1 = new Int32Rect(10, 10, 10, 10);
        var rect2 = new Int32Rect(30, 30, 10, 10);
        var rect3 = new Int32Rect(50, 50, 10, 10);
        var rect4 = new Int32Rect(70, 70, 10, 10);

        var int32Rects = new[] { rect1, rect2, rect3, rect4 };
        var int32Rect = GetValue(int32Rects);
    }

    private static Int32Rect GetValue(Int32Rect[] int32Rects)
    {
        int xMin = int32Rects.Min(s => s.X);
        int yMin = int32Rects.Min(s => s.Y);
        int xMax = int32Rects.Max(s => s.X + s.Width);
        int yMax = int32Rects.Max(s => s.Y + s.Height);
        var int32Rect = new Int32Rect(xMin, yMin, xMax - xMin, yMax - yMin);
        return int32Rect;
    }
}

Result:

{10,10,70,70}
0
votes

The question is somewhat unclear and so I will start of by stating my understanding of what you are looking for. As I read your question, you have a collection of rectangles and are looking to find the smallest rectangle that contains all rectangles in your collection.

Here is what you need to know in order to do this:

  • The top left of a rect is (X, Y) and the bottom right is (X+Width, Y+Height).
  • The width of a rectangle is given by Right - Left. The height is given by Bottom - Top.

Now that you can convert between these quantities the rest is easy. Find the minimum top value, the minimum left value, the maximum right value and the maximum bottom value. Feed those values into the equations in the second bullet point above and you are done.

0
votes

You can save some effort, and avoid being concerned about having "world knowledge" of which Rectangle is bottom-most/top.most left-most/right-most:

public static class RectangleExtensions
{
    public static Rectangle RectsGetBounds(this Rectangle rect, params Rectangle[] rects)
    {
        Rectangle rbase = rect;

        for (int i = 0; i < rects.Length; i++)
        {
            rbase = Rectangle.Union(rbase, rects[i]);
        }

        return rbase;
    }

    public static Rectangle ControlsGetBounds(this Control cntrl, params Control[] cntrls)
    {
        return RectsGetBounds(cntrl.Bounds, cntrls.Select(c => c.Bounds).ToArray());
    }
}