Image Enhancements

Image Enhancements (Gimp - http://www.gimp.org/ - free program similar to Photoshop)

  • View->Zoom (change image view size as appropriate for editing task)
    • Keyboard shortcuts: 1:1 - press "1" key; Fit in Windows - press shift-ctrl-E keys together
  • Image->Scale Image->(use Width/Height Percent or Points to resize image)
  • Edit->Undo (remember you can restore image if you are not happy with changes)
  • Dialogs->Undo History (multiple undos)
  • Tools->Toolbox (ctr-B) brings toolbox to the front - Many Tools menu commands have a toolbox and keyboard equivalent
  • Straighten skewed scans (This is best done in full color mode (Image->Mode->RGB) before any other image editing is begun.)
    • Correct the image orientation if necessary: Image->Transform-> Rotate 90° Clockwise, Counter-Clockwise or Rotate 180°
    • Straighten Method 1:
      • Use the quide rule to determine true horizontal. Drag a guide from the ruler at the edge of the image window. Position the guide at one corner of the bottom of the map edge or text. Do this precisely in 100% zoom (press the "1" key)
      • Use the Rotate tool (shift-R) to align the image with the horizontal guide. In fit on screen view (ctrl-shift-E) move the rotation point to the same bottom map edge you set the guide to. Switch to 100% zoom ("1") to more precisely align the rotation point. Move to the opposite map edge and drag the image to rotate the map edge to match the horizontal guide. Press enter to rotate the image
    • Straighten Method 2: (easiest in Photoshop)
      • Tools->Measure - displays angle of measurement along map line that should be horizontal
      • Tools->Transform->Rotate - enter angle determined above (entered automatically using Photoshop Rotate Arbitrary).
    • Image->Fit canvas to layers (forces canvas to fit rotated image)
    • Use the Crop tool (shift-C) to to remove additional unwanted edge of the image. If you will be combining multiple maps together as image overlays, you may want to remove the map collars from a copy of the rotated image file.
  • Cleaning up Image - Optional (always clean up a copy of original image)
    • Colors->Auto->Normalize or Colors->Levels (to adjust manually)
    • Colors->Maps->Color Exchange (remove color blemishes - paper browning, etc.)
    • Selection area: delete key to clear selected area (clean up sections of image)
    • Colors->Threshold (removes all colors/grays - useful for reducing image size) Image->Mode->Indexed->Use B&W 1-bit palette
  • File->Save As-> (Choose file format needed - jpg, png, etc.)
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