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I have a rather big Geotiff. It is the mosaic of four RapidEye satellite images. They are all a bit bland/grayish. When combined I would like to freshen up their colors so that they are more visually appealing. The imagery will be used as a backdrop for other data.

I have tried right-clicking on the raster in the layers list and selecting Properties. Using Symbology allows for detailed adjustments. But there is no easy way to auto-adjust the image color balance.

Some image software like IrfanView has "auto adjust colors". IrfanView can not open my geotiff image, but this kind of functionality represents what I am looking for.

To the extent I am doing analysis on the imagery I will of course not mess with the color balance.

ragnvald
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  • How about Photoshop or GIMP? –  Nov 19 '12 at 11:31
  • Tried GIMP but it does not work. It loads but gives an error message "alpha channel type not defined for file C:\myfile.tif. Assuming alpha is not premultiplied". – ragnvald Nov 20 '12 at 06:43
  • It loads? Can you go on doing what you want while ignoring the error? I haven't seen that kind of error when handling GeoTIFFs in GIMP before (but I have no experience with RapidEye images).. GIMP to my experience is still rough on the edges when it comes to handling GeoTIFFs –  Nov 22 '12 at 09:57
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    I usually have to preprocess GeoTIFFs with gdal_translate or the other GDAL tools - and preserve the geo-tags with libgeotiff - before passing it to GIMP. I heard Photoshop is better suited than GIMP for this kind of purpose, so I guess that'll be your best bet. If all fails - you can always bite the bullet and use a more full-fledged GIS software like GRASS, QGIS, SAGA, etc.. Wish you all the best ;) –  Nov 22 '12 at 09:58

2 Answers2

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An alternative to the "inlined" TIFF geospatial metadata (the ordinary geotiff-file) is the externalized TFW-file which can hold the geographical reference data. Procedure for export is available in this answer.

The resulting "normal" tiff-file can be subject to edits by any image editor. Remember that resizing of the image will render it useless.

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ragnvald
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You might have some troubles with no spatial software when it comes to reading your geotiff because they will not understand the header values. At least this has been my experiance in the past. Have you tried mosaicing the images together, at least that way you allow you to apply symbology adjustments to the entire images.

dango
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  • Did that. And they merged together rather nicely. Still the colours are bland. I am sure if I messed around with the symbology long enough I would get there. But having an auto adjust for "natural colors" would be better in this case. – ragnvald Nov 20 '12 at 12:24
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    In the passed I've converted geotiffs to other image formats that dont contain headers and worked on them in non spatial software packages like photoshop. During the export from geotiff til ..... say .bmp you should create a world file that way you still have a georeferenced image.This should work fine if the image you are exporting is an 8bit image (values from 0 -255). – dango Nov 21 '12 at 07:32