I have a simple model that calculates the NDVI from bands 3 and 4 of a raster dataset. The input bands are 8-bit unsigned, whereas the default output NDVI is signed 32 bit.
How can I specify the pixel depth for the output NDVI as 8 bit unsigned?
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Can this be controlled with an environment setting?– L_HolcombeFeb 12, 2013 at 15:43
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I haven't found a way to specify the pixel depth in the environment settings.– Aaron ♦Feb 12, 2013 at 16:03
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Does the calculator exhibit behavior that changes the pixel depth?– gm70560Apr 30, 2013 at 21:38
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No as this is part of a model so I need to keep the image with the original 8 bit, do the calculations, convert it into 32bit and do some other calculations and then output it. The problem is to keep it at 8 bit for the first set of calcs.– JohnApr 30, 2013 at 22:03
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Would you be able to edit your question to include this clarification to it, please?– PolyGeo ♦Jul 23, 2013 at 23:12
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2 Answers
The result from NDVI will be continuous (i.e. decimal) values between -1 to +1, therefore the raster must be able to store these values, and will use signed pixel depth. If you truly want 8-bit unsigned, you will need to adjust the expression in the raster calculator by linearly scaling to values between 0-255 and then applying the int() function on the entire calculation. However, this still does not guarantee that the output will be 8-bit unsigned. Perhaps try Copy Raster on the scaled raster with the optional pixel_type parameter in your model to help with this.
After running Raster Calculator, use the Copy Raster tool with the pixel_type parameter set to 8_BIT_UNSIGNED, as shown below.
