Joining and Aligning two images into one – Floor Plan

WM
Posted By
Whitney_McBee
May 11, 2004
Views
556
Replies
10
Status
Closed
Hello All,

I really hope someone can help me to find the best way to do the following.

I have a floor plan that I needed to have available on the computer. We can not get the digital floor plan form the architect as that architect no longer exists. The problem is that the paper copy I have is too large for our 11 x 17 scanner. So, I have scanned the floor plan in two sections and now I need to join and align the two sections.

I’ve tried doing this by increasing the canvas size for the 1st section with the content pushed to the left (since I need to add the other side to the right). But my problem is in getting a good alignment. One or both of the scans always seems to be at least slightly tilted, which makes alignment very difficult.

By the way the scan is a black and white line art. But, I have had to convert it to Gray scale so that I can add another layer (at 50%) opacity to aid in alignment.

I figure there has got to be a better way to do this.

Your help is greatly appreciated.
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Mike_Ornellas
May 11, 2004
nope
PC
Pierre_Courtejoie
May 11, 2004
To find perfect alignment, use difference as the blending mode. An excellent tutorial that conveys that info is available at: <http://retouchpro.com/tutorials/?m=show&id=125>
AS
Ann_Shelbourne
May 11, 2004
With the two scans on separate layers, you should be able to use Transform/Rotate to align one to the other.

Assuming that you have black-lines on white, turning the top layer to "Multiply" mode should let you see what you are doing.
R
Ram
May 11, 2004
It just might be easier to take a digital photograph of the entire floor plan, using a sturdy tripod and a high quality digital SLR with a prime lens and making sure the floor plan is perfectly flat against a wall or something like that.

Just a thought.
DK
Doug_Katz
May 11, 2004
<<We can not get the digital floor plan form the architect as that architect no longer exists.>>

Poor architect.
MH
Mark_Hannon
May 12, 2004
With the two scans on separate layers, you should be able to use Transform/Rotate to align one to the other.

Assuming that you have black-lines on white, turning the top layer to "Multiply" mode should let you see what you are doing.

This is usually how I do it but the only thing I would add is to make use of the little crosshairs in the center of the Transform bounding box.

What I usually do is to line up a point where a distinctive shape overlaps in the 2 layers and then I move the crosshairs/pivot point to that spot. Now when you rotate the top layer, the area where the pivot point is will stay alligned so you just have to find the correct rotation angle where the rest of the 2 images line up.

One other thing I do is to use a soft edge eraser brush on the edge of the top layer image. I find it creates a smoother transition between the 2 layers. Don’t forget to turn the top layer’s blending mode back to "Normal" before you merge the top layer down.
CS
Carl_Stawicki
May 12, 2004
Since it’s a floor plan, there are probably some common vertical or horizontal lines running through both pieces. You can use one of these lines to perform an arbitrary rotate with the help of the the Measure tool. The scans will end up being squared-up the same, give or take a few pixels. If there are no common lines, draw a light pencil line on the original prior to scanning to use as a reference.

Carl.
WZ
Wade_Zimmerman
May 12, 2004
I do this all the time with renderings and floor plans the problem here is a little different then what was suggested in the tutorial. the reason one or both plans seem a little titled is that they are as they will protrude over the edge of the scanner and of course one end is lower that the other.

You can deal with it the same way as in the tutorial and might consider a slight adjustment for each section with the Transform > Perspective or Distortion. What you are looking to do is get the height to be plum, squared off first that is same on both ends.

Rotation might also be required. It never really works out 100% but you can make it as accurate enough that only you will know.

You can do it with a digital camera except you will need a properly aligned copy stand or you will probably be still in need of squaring up the plan.

If you photograph are work a lot then it is no problem but if not you are in for a treat. Even lighting and all that stuff.

Now the real advice take it to a service that does large format scanning or to another architectural firm who would probably have an 11×17 scanner.
AW
Allen_Wicks
May 12, 2004
What Ann said. On an oversized canvas I would use reference horizontal/vertical lines on the overlapping portion of each layer to validate alignment and scale of scan a versus scan b. Then after aligning and scaling I would erase overlaps as necessary.

Unless you use a tilt/shift lens (and perhaps even then) a photograph would be distorted.

11×17 scan should be easy to find at a service bureau – unless you live where I do!
J
jonf
May 13, 2004
My own 2¢ … when I’ve had to do this, I find it’s a little easier to crop each scan to correctly square up before attempting the merge. I just find the crop interface is faster and easier to deal with than the transform tool. Since this is a floorplan I assume there are plenty of horizontal and vertical lines to use as reference guides. Align the edge of the crop area with any one of these lines, then expand the crop area from the corners (to encompass the whole image) before applying it. Do that to both scans and merging them is a snap.

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