Plot lines by rectilinear coordinates

[jschuchert]

I want to be able to plot points and lines by coordinates. For example, a figure has rectilnear coordinates at a corner like 1234.23 N , 4567.123 E, etc. The user enters point numbers, each containing coordinates and the program draws the lines between them. I looked at the program designed by Klaus that is close to what I am after but his coordinates were within the confines of the actual screen pixels. How do I use my own coordinate system so that the lines will be accurate. I am used to numbers increasing as they go UP and to the right. Although they increase going right, they increase going DOWN with a PDA screen. I think I have done this before with another software but can't find it. This is not for CAD (beyond my small brain) but just a simple plot. Thank you for your help.

Jim Schuchert

 

[klaus]

Hi Jim,
What programs did you look at ?
If you have a look at the B4PPc Graphics Tutorial in the 'DrawOnScaleImage' chapter you have what you need. You can determine a bitmap with a given size and enter the coordinates of the upper left and the lower right corner.

You will need following variables and equations:
ScreenX0 = pixel coordinate of the left edge of the visible screen on the device
ScreenY0 = pixel coordinate of the upper edge of the visible screen on the device
ScreenW = width of the bitmap in pixels
ScreenH = heigth of the bitmap in pixels
xphysic0 = x coordinate of the upper left corner in physical coodinates
yphysic0 = y coordinate of the upper left corner in physical coodinates
xphysic1 = x coordinate of the lower right corner in physical coodinates
yphysic1 = y coordinate of the lower right corner in physical coodinates
ScaleX = (xphysic1-xphysic0)/ScreenW -> 1 pixel = ScaleX physical units
ScaleY = (yphysic1-yphysic0)/ScreenH -> 1 pixel = ScaleY physical units

Equations to transform x, y form pixels to phyiscal coordinates:
xphysic = (x - ScreenX0)*ScaleX + xphysic0
yphysic = (y - ScreenY0)*ScaleY + yphysic0

Equation to transform x, y physical coordinates to screen pixels
xpixel = (x - xphysic0)/ScaleX + ScreenX0
ypixel = (y - yphysic0)/ScaleY + ScreenY0

With this you can also have numbers inceasing UP, in this case ScaleY is negative instead of positive.

Hope this will help.

Best regards.

 

[jschuchert]

Thank you very much, Klaus. I am sure I will find what I need here. The program I referred to was "snappointskalus".

Jim

 

[klaus]

What program is this one "snappointskalus, I don't remember it".

Best regards.

 

[jschuchert]

It was a reply to a post by 'dennisshea' in May,2008. You had the file zipped at the end of your post. I found it by typing 'drawing programs' in the search box. It is the second post down. Incidentally, if I knew how to attach a link from the forum I would have done it.

Jim

 

[mjcoon]

... Incidentally, if I knew how to attach a link from the forum I would have done it.

In each forum item at top right there's a link called "permalink". You can copy this (something like right-click and "Copy", depending on browser).

Then paste it into the new item, perhaps using the "globe/chain" icon called "Insert Link".

HTH, Mike.

 

[jschuchert]

Thank you very much. Now there's something else I know. You guys are great.

Jim Schuchert