[aprssig] Image maps for WinAPRS

Stephen H. Smith wa8lmf2 at aol.com
Wed May 25 16:30:54 EDT 2005

nkotch at earthlink.net wrote:

>1)  What other graphic programs will give you pixel coordinates of an image
>file?   I tried with photoshop and macromedia fireworks but couldn't find a
>way to get a pixel coordinate, and finally just tried paint and it did.  
Photoshop is perfectly capable of showing coordinates.  Pulll down 
"Window, Show Info".  The resulting screen will not only show 
coordinates; it will also display the RGB values for the pixel you are 
currently hovering over,  the same information in HSB (hue, saturation, 
brightness format) and the size of the pick or crop box when you drag 
one out.

>2)And, I'm guessing that using an image file for a map only really works
>when the original image was already made to scale and is fairly accurate to
>begin with.  What if the image was not drawn to scale?  Is it better/easier
>to try and make your own instead of trying to "fix" that one or does it get
>to difficult. 
The key requirement is that the map be a simple rectangular display with 
longitude lines shown as being straight and parallel instead of being 
curved and converging at the poles as they do in real life.  Most small 
area (city or county level maps) will be this way (or diverge from it so 
slightly that it's not a problem).  Larger area maps (state level, 
regional or higher) are normally projected with some non-linear display 
to minimize distortion, make equal-sized area look equal sized, or some 
combination thereof. 

If the area is not too large, you can sort of "split the difference" by 
calibrating points a quarter of the way in . or so, from each corner.   
Error will increase as you move toward the corners or toward the center, 
but never be as great as they would be if you calibrate at the extreme 

>3)Also, what are some of the ways that ya'll have made your own image maps?
>For an event like this it was great to have a simple map like this with the
>course already laid out, and major streets marked.  I have tiger maps w/
>street level detail installed but to view the entire course I would have had
>to zoom out to where I couldn't see all the streets and if someone wanted to
>come by and see where the Tail biker was I would had to of zoom in and move
>the map, instead of just leaving the entire course up that is simple and
>easy to see.  Luckily the race people already had this made but what if it
>isn't?  Have ya'll just gotten creative with photoshop, or started with a
>Street Atlas map, or other ideas?   
You can do screen caps of any map image on your screen.  Just punch the 
"Printscreen" key on your keyboard once or twice.   Then open a graphics 
app like Paint or PhotoShop and do an "Edit, Paste" (usually Ctrl-V on 
the keyboard does the same thing).

 You will get a picture of the entire screen, including the Windows 
widgets (task bar, scroll bars, etc.)   pasted in.  Then use the 
bounding box tool to crop out only the part you want and save it.  I 
usually switch my screen to a resolution far higher than I normally use 
everyday, in order to capture a larger area of a high-res map than I 
would otherwise.    When you later view the oversized image at a lower 
screen res, you will see only a part of it at one time and will be able 
to scroll it to view the other parts. 

A couple of FREEWARE utilities that are very useful for this kind of 
stuff are:

 IrfanView -- the Swiss Army knife of graphics utilities. Opens 
virtually any graphics format known to man, can resize, crop and save 
into nearly other format, do automated screen caps directly to file, 
create free running automated slide shows, play MP3s, MPGs, AVIs, etc, 
thumbnail directories of images and so much more.  The program is tiny 
(less than 1 MB) and loads instantly even on lesser systems.  It can 
even do many of these functions from command lines or DOS-style batch 

Gadwin Systems Printscreen -- restores the direct single-keystoke 
printscreen  function that existed in DOS to Windows systems.  It can be 
configured to either print to paper via a designated printer, or capture 
to a file in your choice of formats (GIF, TIF, BMP, JPG, etc), or both 
each time you hit the print screen key.  A nice feature is that unlike 
brute-force fullscreen captures described above, it can be configured to 
capture only the current contents of the current open window, minus 
menus, toolbars, etc  so that the image is already cropped and ready for 


Stephen H. Smith             wa8lmf (at) aol.com
Home Page:                   http://wa8lmf.com

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