Question

I am creating a Rect in C# with two points. These points are actually Geographical bounds. The problem I am having is what when I create the rectangle the y axis is flipped.

For example say my data is west="5.42194487004" south="46.407494" east="17.166386" north="55.056664"

I pass that into Rect geoBounds = new Rect(new Point(west, north),new Point(east, south));

The Rectangle that is created has the following properties

    Bottom  55.056664          double
    Height  7.781945           double
    IsEmpty false              bool
    Left    5.864166           double
    Right   15.038887000000003 double
    Top     47.274719          double
    Width   9.1747210000000017 double
    X       5.864166           double
    Y       47.274719          double

The Y axis is flipped. I have triple checked that the data being fed into the call is correct. What is wrong? Also I know that I did not supply much code but did not feel any more was needed. Will provide more if needed.

Answer 1

The coordinate system has 0,0 at the top left of the screen, with Y increasing in the downward direction. You can see this at the example page for the Rect.Bottom property: http://msdn.microsoft.com/en-us/library/system.windows.rect.bottom.aspx

Note on that page this comment:

// Bottom property gets the y-axis value of the bottom of the rectangle.  
// For this rectangle the value is 55.
rectInfo = rectInfo + "Bottom: " + myRectangle.Bottom;

and this one:

// Top property gets the y-axis position of the top of the rectangle which is  
// equivalent to getting the rectangle's Y property. 
// For this rectangle the value is 5.
rectInfo = rectInfo + "| Top: " + myRectangle.Top;

This is further supported by the explicit constructor for Rect: http://msdn.microsoft.com/en-us/library/ms587929%28v=vs.95%29.aspx

Note that x and y describe the top left corner, where width extends that in the rightward direction and height extends downwards.