arcgis-desktoperdas-imaginegeotiff-tiff
My tif image data type is float (i.e. my data is between -1 to +1) and I want to convert it into 8bit unsigned integer.
I used ERDAS IMAGINE import tool to do this, while converting it into img also.
However, in the output image the data is only shows 0 and 1.
I want to convert -1 as 0 and +1 as 255.
How can I do this in ERDAS IMAGINE and ArcGIS for Desktop?
I just did some basic tests, converting a raster to a binary mask by performing a Con, which created an 8-bit output. From there, I could use Copy Raster to convert the output to a 1-bit raster:
arcpy.CopyRaster_management("in_raster", "C:/workspace/foo.img", "", "", "", "", "", "1_BIT")
I confirmed that ArcGIS and GDAL both see this as a 1-bit raster. For other formats, 1-bit output may not be possible, the limitations for each format are listed on the supported raster formats page.
If you are really pushing for the smallest possible files, there are even some other tricks you can use:
Disable Pyramids, with:
arcpy.env.pyramid = "0"
Make sure that you're using an appropriate compression setting arcpy.env.compression for the output raster. LZW is a good default, but if you are working with 1-bit rasters, you can push things even further with the CCITT family of compression algorithms, originally designed for Fax machines. You can set this with:
arcpy.env.compression = "CCITT_1D"
The two environment settings I mentioned here can also be added to the environment of the geoprocessing tools, under "Environment > Raster Storage".
If none of this works for you, would you be able to share a piece of your data for us to test against?
You will want to stretch your floating point data from (-1 to 1) to (0 - 255). You can accomplish this very easily in Erdas Imagine:
Raster tab > Resolution Group > Radiometric > Rescale
Best Answer
You could try Linear Contrast Stretch (Linear Contrast Stretch, Pg 145) in ERDAS IMAGINE. This tool will assess the minimum and maximum DN/pixel value in your image and stretch it in the range of 0-255.
The same can also be done using ArcGIS, as you required. Linear Stretch using ArcGIS.
This is a form of radiometric enhancement of the image, wherein you can shift the min-min values of the image as desired....
Let me know if this helps, and happy to help with more queries until you get your results...