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I need to make from my ArcMap layers (which are georeferenced JPEG files) a file that can work on a free and easy to use program.

The program needs to be able to open multiple layers so we can put them on top of each other and to be able to change the transparancy of the layers.

Does anybody know a solution?

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    Except for the change in transparancy part, you can use layered pdf files. Works with all major pdf readers. With large rasters you might get very large pdf files though.
    – Martin
    Commented Apr 23, 2014 at 9:55
  • I think ArcReader supports transparency on layers in its Table of Contents.
    – PolyGeo
    Commented Apr 23, 2014 at 10:06
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    You should also know that JPEGs by themselves do not support transparency. Maybe you mean something else by the usage of that word? Commented Apr 23, 2014 at 10:18
  • @DevdattaTengshe Good point - perhaps asker just means on/off visibility - in which case Export Map to layered PDFs would then seem ideal to meet asker's requirements - although it also suggests layers cannot be pre-authored which may rule that and ArcReader out.
    – PolyGeo
    Commented Apr 23, 2014 at 10:39
  • @PolyGeo: On second reading, maybe OP could also be referring to changing the Opacity of the layers. Maybe a slider where they could make the the whole layer transparent, to completely opaque. Commented Apr 23, 2014 at 10:47

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Assuming you're trying to use it within a GIS-system, QGis does the trick.

It's a free GIS-system, and you can set transparancy layer-based, toggle layers on and off, switch around the order, ... Whereas - to the best of my knowledge - Arcview or MapInfo's Proviewer do not offer the option to combine layers.

That said, transparancy and opacity are not entirely the same, so I'm not sure which you're after. (opacity lets you 'see through' but still have the original colors in a lighter form, transparancy replaces certain colorshades with 'nothing').

In georeferencing images, I tend to set the 'extra' areas which I don't need to white using a photoeditor, and then set a transparancy filter to set '255 255 255' color combination in QGis to transparent. Works like a charm, but might not be what you're trying to achieve.

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  • It is easy, as you mention, to combine rasters in QGIS but there is a way to do this in ArcGIS using Image Analysis, Stretch & Pansharpening functions but it takes a bit of an effort to set up. Commented Apr 23, 2014 at 18:17
  • Yup, but ArcGIS isn't exactly free software, as was requested in the initial post. Frankly, it'd be disappointing if paid software wouldn't allow to do it. Commented Apr 24, 2014 at 6:44
  • I am not disputing your answer. Just making a comment WRT to ArcGIS functionality because you said that to your knowledge ArcView does not have this functionality. Commented Apr 24, 2014 at 14:27

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