Determining lenth and height off screen coordinates

[awayne]

I am using PixelCheckSum and I am wanting to make sure the coordinates I am using are covering say the same area using a rectangle.  Is there math etc to make sure I am covering the same area.

My ultimate goal is to have a stored checksum as a scalar variable and look in an area on the screen and determine if the checksum value exist in that area.  When I am creating the initial variables I need to make sure my look at area is going to be the same size rectangle as my initial value.

Thanks to all who reply

[awayne]

A LOT OF Googling answered my question.  I will have to play around with this to get the length and width values from coordinate values it appears they are subtracting.  Also can do perimeter.  Good ol geometry.

http://www.mathopenref.com/coordrectareaperim.html

I will likely script something to make sure my coordinate grabs are equal in area.

A side question how can I make sure that smoothing is turned off since that can create conflicting checksum values??  I will be honest I am not even certain I know what smoothing is.