Monday, May 14, 2012

Re-align a raster image to the corners in Gimp

The free and open source software Gimp is an Adobe Photoshop like software that can be used to edit or adjust raster images. If you use the Gimp software for editing raster images for contrast, brightness, color balance, etc. then it just might be possible to make a mistake and shift the entire raster image layer so that it is no longer align to the canvas corners. The screenshot below shows a shaded relief raster image that has been mistakenly shifted - the bottom right is no longer aligned to the corner.

In order to shift the raster layer back precisely, the Gimp ruler guide lines can be used as described below.

  1. In the Gimp Toolbox, click the Zoom tool and zoom closer to the corner.


  2. On the top horizontal ruler bar, press down the left mouse button and drag out a horizontal guide line until it snaps to the bottom of the canvas.


  3. On  the left vertical ruler bar, press down the left mouse button and drag out a vertical guide line until it snaps to the right of the canvas.
  4. In the Toolbox, click the Move tool. Press down the left mouse button on the raster image and drag the image so that the bottom right corner snaps  to the horizontal and vertical guide lines.

    The raster image is snapped to the canvas corner.


    The raster image is now correctly aligned again.
     

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