Mosaic Dataset Aerial Photography Color Balance

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04-03-2014 10:56 AM
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I am working with historic aerial photography over Panama to observe the change in forest cover over time. All of the frames have been added to a mosaic dataset with shrunken footprints and seamlines. All images have had the grayscale function applied as well at 8 bit depth.

The issue I'm running into is with the color balancing tool. Each frame has artifacts that I've minimized with another software (MaxIM DL) with gradient removal and flat fielding. My goal is to color balance the images and perform a histogram matching on the mosaic so that pixel values are consistent throughout. The error I receive follows: "Color correction does not currently support data with colormaps. Color correction will not be applied." When I try the delete colormap tool it claims that the input raster does not have a colormap.

Has anyone run into a similar situation when mosaicing aerial photography? Any advice would be much appreciated.
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I am working with historic aerial photography over Panama to observe the change in forest cover over time. All of the frames have been added to a mosaic dataset with shrunken footprints and seamlines. All images have had the grayscale function applied as well at 8 bit depth.

The issue I'm running into is with the color balancing tool. Each frame has artifacts that I've minimized with another software (MaxIM DL) with gradient removal and flat fielding. My goal is to color balance the images and perform a histogram matching on the mosaic so that pixel values are consistent throughout. The error I receive follows: "Color correction does not currently support data with colormaps. Color correction will not be applied." When I try the delete colormap tool it claims that the input raster does not have a colormap.

Has anyone run into a similar situation when mosaicing aerial photography? Any advice would be much appreciated.


Casey,

If your images from MaxIM DL are suspected to have �??inherent-colormap�??, you can verify and work around.  Please use other packages like ERDAS or ArcGIS importing into IMG/ TIFF first, and then load into MD for CB testing�?�

On CB (color balancing) on �??grayscale�?? images, pls try to use 10.2.1. It should work fine�?�

Plese share your finding...


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If yes with �??inherent-colormap�?? (i.e., the issue still exists, after importing into IMG /TIFF), it is better to check if the saving-image process used �??Auto Stretch�?? in MaxIM DL, during processing image (stretching, adjusting, etc.). Mostly, you can try to adjust the stretch �??manually�??, before saving...
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Thank you for your comments. I have been able to work around the colormap issue and the images will color balance fine. I experimented with a work around by simply creating a colormap on the individual image files and then turning around and deleting the new colormap. A strange work-around but resulted in the desired effect.

I have had some luck with the mosaic dataset work but am now running into an issue exporting the final mosaic dataset product as a TIFF. I have tried all ways to export, i.e. the "export as different raster type", simply right clicking on the image in TOC and exporting that way, etc.

The export will produce an image of the same extent as the mosaic but displays "choppy", that is that there will only be strips or slivers of the image and most of the center is blank. I am exporting these as TIFFs and have tried the rendering option for an 8-bit unsigned. Most of the mosaics are ten images or more but I've tried mosaicing four or five to see if that works. These do export appropriately but I do not like the product of exporting parts of my aerial coverage and then mosaicing those exports together. The histogram matching does not work properly in this case.

I personally have never seen this issue occur while exporting where only slivers of the image export but it is a major problem. Thanks in advance for any advice.

Casey
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Great, the workaround looks ok, ...

On 'export�?? from MD, it should work fine with 10.2/10.2.1, if the exported image format in (IMG) is used (as long as MD is good).
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I would like to keep the files as TIFFs if possible but I gave your suggestion a try. Exporting as an IMG produces the same incomplete result.
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I would like to keep the files as TIFFs if possible but I gave your suggestion a try. Exporting as an IMG produces the same incomplete result.



On removing gaps and slivers among scenes, please refer to the GP tool at http://resources.arcgis.com/en/help/main/10.2/index.html#//001700000087000000



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Here, I gave some BASICS/ thoughts on why 'suspected' colormaps cause issue, which should be removed before adding into MD...



Look-up Tables vs. Colormaps


[INDENT]LUTs (Look-Up Tables) are fundamental to many aspects of image processing. An LUT is simply a table of cross-references linking index numbers to output values, which is widely used in remote sensing and photogrammetry.

In cartography or GIS, however, the most common use is to determine the colors and intensity values with which a particular image will be displayed, and in this context the LUT is often called simply a �??colormap�??.

One disadvantage of using a colormap is that it introduces additional complexity into an image format. It is usually necessary for each image to carry around its own colormap, and this LUT must be continually consulted whenever the image is displayed or processed.

Another problem is that in order to convert from a full color image to (say) an 8-bit color image using a color image, it is usually necessary to throw away many of the original colors, a process known as color quantization. This process is lossy, and hence the image quality is degraded during the quantization process. Additionally, when performing further image processing on such images, it is frequently necessary to generate a new colormap for the new images, which involves further color quantization, and hence further image degradation.

As well as their use in colormaps, LUTs are often used to remap the pixel values within an image. This is the basis of many common image processing point operations such as thresholding, gamma correction and contrast stretching, which is very common in some photo processing packages. The process is often referred to as anamorphosis.[/INDENT]
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