Establish the scanning
width of your scanner and subtract about a half inch (1 cm) minimum to allow
for map section overlap. Call this measurement SW.
For this technique it is assumed your map shortest side is less then the scanner height x 2 - if it is not you will have to scan an extra group of images through the middle of the map, a difficult task to keep them square and not covered in this document.
Notes : You need a lot - at least 150Mbytes of free space on drive C: (virtual memory drive) to do the process. The more RAM the better.
Establish the scanning
width of your scanner and subtract about a half inch (1 cm) minimum to allow
for map section overlap. Call this measurement SW.
Divide the long side of
the map into enough equal sections so that the width of each section is less
the measurement SW. I usually end up with 4 sections.
On the back of the map
mark each section at the top and the bottom of the paper.
If you can remove the
lid from the scanner, it makes it much easier, if not prop it up with something.
Set the scanning software
to 256 colors and 125 dpi, do some experimental scans to determine
the best brightness/contrast settings, it is better to get these correct
before scanning, write down the best settings for use the next time you scan
a map. DO NOT alter these settings between sections of the same
map. I will assume you are going to save the sections as TIF images (do not
use jpg images as these need 16 million colors). Do not be tempted to use
more than 256 colors it provides no advantage but increases the amount of
RAM required to manipulate the images. Do not use more than 125dpi and assume
you can resize later, the scanner does a much better job of sizing and not
loosing information than most software.
Position the top right
corner of the map (back view) onto the scanner making sure it is pressed
tightly against (or lined up with) the top edge of the scanner glass. It
is important to do this to make sure all sections are kept as square as possible.
Use a book and other objects to keep the map pressed firmly on the glass
especially near the edges where distortion is most likely.
Scan this section and call it X1.TIF
This image shows the map positioned on the scanner for the 1st section.
Slide the map to the right
so the right hand side of section 2 is lined up roughly with the right hand
edge of the scanner glass. Press the top of the map tight against the top
edge of the scanner glass. Scan this section and save as X2.TIF
Repeat this operation
for section 3 and 4.
Now rotate the map 180
degrees and put the upper right corner on the scanner pressing the right
hand edge and more importantly the top of the map against the top edge of
the scanner glass. Scan this section as X5.TIF
Repeat for sections 6,7,8
as before.
For this we will use Paint Shop Pro version 4 which is available as shareware.
Open Paint Shop Pro (PSP).
Load in image X1.TIF -
examine the image, some maps are printed so the long edge of the paper is
left to right and others have the long edge top to bottom. Depending on your
map you may have to rotate the image to get it upright. If necessary do
this now - select Menu options Image/Rotate and rotate in the
required direction.
Now the image has to be
resized to fit the remaining sections. The size of the section is shown at
the bottom right hand side of the PSP screen (Width x Height x Num colors).
I you did not rotate the section multiply the Width by 4 (we will call this
TW), multiply the Height by 2 (we will call this TH). If you did rotate the
image 90 degrees multiply the Width by 2 (TW) and the Height by 4 (TH).
Select menu option
Image/Enlarge canvas. Set the width to TW and the height to TH, do
not centre the image, press OK.
Select the Menu option
File/Save As and save the image under a new name.
The image is probably
zoomed - zoom back to 1:1 - right now.
The following sequence
is repeated from here for each section.
Use File/Open and
load X2.TIF - if necessary rotate image to vertical - make sure the X2.TIF
image window is still selected and select the menu option Edit/Copy -
this copies the entire image to the clipboard - close image X2.TIF, do not
save when asked.
Press the selection button
on the button bar - right now.
Scroll the image until
the edge you are going to join to comes into view - important.
Select menu option
Edit/Past/As New Selection - the X2.TIF image is pasted into the image
as a selection box - be careful not to click the mouse outside the selection
box otherwise it will pasted permanently at that position. Ok the selection
box should be filling the entire viewing window, do not be tempted to zoom
out at this stage it will only slow things down - use the mouse and drag
the selection box until you can see its edge, do this carefully and slowly
- using whatever means you can line it up with the map section which is already
there, it is OK to scroll to check along the join, try to get an exact as
possible a match with the existing section as this determine how accurrate
the map will be. When you are happy with the join click outside the selection
box to make it permanent. If you make a mistake be prepared to reload where
you were up to and start the section again.
Tips for Advanced users - when you have become confident with the above technique there are other variations which make joining the sections easier. 1. Before pasting the next section into the image, zoom out to about 10:1 (or whatever) and then paste the section, this allows you to see the selection and slide it roughly into position much easier. 2. Select 1:1 zoom to slide the section closer to its position and 3. To make it easier to line up the pixels to join each section zoom in to 1:2 or 1:3 etc (enlarge the image), this makes it much easier to slide and see where the pixels align.
Save the image. It is
also advisable to save the image using different names occassionally as you
join sections so you have more than only 1 copy, it is very easy to corrupt
the image you are working on and it is good to have a backup.
Repeat for sections
3,4,5,6,7,8 - keep in mind that section 5,6,7,8 will always need to be rotated
to get them upright.
When you have joined all
sections and now have a complete map you need to cut the rubbish from around
the map. Zoom out until you can see the entire map and mark the extent of
the map you want using the selection tool. Use the menu option Image/Crop
to remove the unwanted part of the image.
Save the map image and
you are finished