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Hi all, </div>
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I’m trying to mask a band from a GeoTiff file like so:</div>
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<div><font face="Courier">>>> from osgeo import gdal, ogr, osr</font></div>
<div><font face="Courier">>>> from gdalconst import *</font></div>
<div><font face="Courier">>>> import numpy as np</font></div>
<div><font face="Courier">>>> import matplotlib as mpl</font></div>
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<div><font face="Courier">>>> dataset = gdal.Open('001.tif')</font></div>
<div><font face="Courier">>>> band = dataset.GetRasterBand(1)</font></div>
<div><font face="Courier">>>> ba = band.ReadAsArray()</font></div>
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<div><font face="Courier">>>> print "Origin:", ba[0, 0], type(ba[0, 0]) # NODATA value in image == zero</font></div>
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<pre style="box-sizing: border-box; overflow: auto; font-size: 14px; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">Origin: 0 <type 'numpy.uint16'></font></pre>
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<div><font face="Courier">>>> print "(5, 5):", ba[5, 5], type(ba[5, 5])</font></div>
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<pre style="box-sizing: border-box; overflow: auto; font-size: 14px; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">(5, 5): 42271 <type 'numpy.uint16'></font></pre>
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</font></div>
<div><font face="Courier">>>> print "Nodata:", band.GetNoDataValue() # NODATA from file == None</font></div>
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<pre style="box-sizing: border-box; overflow: auto; font-size: 14px; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">Nodata: None</font></pre>
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</font></div>
<div><font face="Courier">>>> print "Mask flags:", band.GetMaskFlags()</font></div>
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<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">Mask flags: 1</font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier"><br></font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">>>> band.SetNoDataValue(0) # Set the NODATA value to zero
>>> print "Nodata:", band.GetNoDataValue(), type(band.GetNoDataValue())</font></pre>
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<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">Nodata: 0.0 <type 'float’></font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier"><br></font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">>>> mb = band.GetMaskBand()
>>> ma = mb.ReadAsArray()
<br></font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">>>> print "Origin:", ma[0, 0], type(ma[0, 0]) # *** SHOULD BE ZERO!!! ***
</font><pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">Origin: 255 <type 'numpy.uint8'></font></pre></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier"><br></font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">>>> print "(5, 5):", ma[5, 5], type(ma[5, 5]) # Correct</font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">(5, 5): 255 <type 'numpy.uint8'></font></pre></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier"><br></font></pre>
<pre style="box-sizing: border-box; overflow: auto; padding: 0px; margin-top: 0px; margin-bottom: 0px; line-height: inherit; word-break: break-all; word-wrap: break-word; border: 0px; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; white-space: pre-wrap; vertical-align: baseline;"><font face="Courier">>>> print np.any(ma==0) # Mask band is entirely 255</font></pre>
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<div style="color: rgb(0, 0, 0); font-size: 14px;"><font face="Courier">False</font></div>
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As you can see, the mask covers the entire image and not the zeros on the edge. </div>
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The band.GetNoDataValue() is returning a Python float() which leads me to suspect that there is incorrect type handling within GDAL’s Python wrapping such that the mask generation is trying to compare the band’s raster values (GDAL_UInt16) to whatever the NoDataValue
type is stored internally. Am I way off base or is there something I’m missing?</div>
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Cheers!</div>
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<div style="color: rgb(108, 108, 108); margin: 0px;"><span style="font-size: 13px;">Dave Welch <span style="color: rgb(250, 167, 87);">Software Engineer</span></span></div>
<div style="color: rgb(108, 108, 108); margin: 0px;"><span style="font-size: 13px;">URTHE<span style="color: rgb(250, 167, 87);">CAST</span></span></div>
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