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Multi-band to Single-band image conversion   William Patterson Feb 19, 2008
Re: Multi-band to Single-band image convers...   Robert Berger Feb 28, 2008
Re: Multi-band to Single-band image convers...   William Patterson Feb 28, 2008
Re: Multi-band to Single-band image convers...   Dan Patterson Feb 28, 2008
Re: Multi-band to Single-band image convers...   William Patterson Feb 28, 2008
Re: Multi-band to Single-band image convers...   Robert Berger Feb 29, 2008
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Subject Multi-band to Single-band image conversion 
Author William Patterson 
Date Feb 19, 2008 
Message Hello,

Is there a tool or procedure in ArcGIS Desktop to convert multi-band images to single-band. We have some topo map scans that are multi-band and would like to batch convert them to single-band. I can do this in a product like Paint Shop Pro or Photoshop (one at a time), but wondering if there's a similar functionality in ArcGIS.

Thanks,

Will
 
   
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Subject Re: Multi-band to Single-band image conversion 
Author Robert Berger 
Date Feb 28, 2008 
Message Will,

you can use the composite band tool (if you only load a single band rather than the whole image) to "extract" a single band from a dataset. To do this, open the composite band tool, maneuver to the dataset and double click (don't hit Add) to see the individual bands. That should work.

Robert 
   
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Subject Re: Multi-band to Single-band image conversion 
Author William Patterson 
Date Feb 28, 2008 
Message Robert,

Thanks for the reply. Yes, I am aware of being able to just extract or grab one of the bands from a multi-band image. I'm not sure that will what I need.

More specifically what I'm looking for is a batch way to reduce the color depth of many multi-band images.

For example, a useful application of this is for scanned map images. Many people who scan them do so at high color depth settings (like 32K or 62K colors - 24 bit) when all they really need is 256 or less colors - 8 bit). These high color images take up 3x as much space (or more) to store all those extra unnecessary colors. In some imaging programs I've seen options to "decrease color depth" which basically filter the colors from all bands down to just 256 or less using some kind of algorithm. This would be a GREAT tool addition to ArcToolbox.

I suppose I could just take one of the bands (R, G, or B) and apply a color map to it to make an indexed color 8-bit image, but I don't think that will work properly, and I'd have to make a colormap on my own.

Will 
   
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Subject Re: Multi-band to Single-band image conversion 
Author Dan Patterson 
Date Feb 28, 2008 
Message http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?id=1653&pid=1644&topicname=Copy_Raster_(Data_Management)
allows you to specify the output specs, a batch version could be generated if you have numerous to do and the output type is the same using Python 
  Geomatics, Carleton University, Ottawa, Canada 
   
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Subject Re: Multi-band to Single-band image conversion 
Author William Patterson 
Date Feb 28, 2008 
Message Dan,

Thanks. I wasn't aware of that tool or its options. This is close to a solution but isn't what I need.

The tool has an option to specify a new output pixel type, but in the help for the tool it says:
"There will be no rescaling of the raster values when a different pixel type is chosen." It is this rescaling of the values that is needed.

I did try some experiments with the tool, and it did some interesting things, but not what I need. When I tried to convert a multi-band 24-bit image to a signed 8 bit image, it still left the output image as 3 bands (multi-band). I need something that converts multi-band to single-band color indexed (with a colormap).

The tool has a "Colormap to RGB" option, but unfortunately no option that does the opposite "RGB to Colormap".

Paint Shop Pro software has an option to decrease color depth from 24 bit to 8 bit (256 colors) and creates a colormap at the same time. It offers choices such as "Optimized median cut" for the output palette and "Nearest color" as the reduction method. It would be great if these type of options were available in ArcGIS.

Will

 
   
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Subject Re: Multi-band to Single-band image conversion 
Author Robert Berger 
Date Feb 29, 2008 
Message Will,

the only other thing I can think of for now would be to load your data into ArcMap and us the renderer etc to make the data look the way you want it (stretched renderer for example for single band)... and then use the export data dialog and "use renderer" to get the data into the format that you want. The dialog will tell you if the output is 1 band etc. I am not sure if the renderer offers the functionality that you need in order to get the output you are looking for. You'll have to play around with it...

Robert