I've discovered that he bands are determined by the args to driver.Create() that is if I create a 4 band image then the bands are correct, however if I'm going to copy the image chunk around using ReadAsArray and WriteArray, doesn't it mean I need to retreive each band in turn?<div>
Or have I missed something and there's an easier way to extract a portion of an image and write it out?</div><div><br></div><div>Cheers,</div><div> Graeme<br><br><div class="gmail_quote">On Mon, Nov 28, 2011 at 3:40 PM, Chaitanya kumar CH <span dir="ltr"><<a href="mailto:chaitanya.ch@gmail.com">chaitanya.ch@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Graeme,<br><br>You do need to copy all bands. Also, make sure you set the correct number of bands while creating the destination dataset.<br>
<br>Color interpretation is useful when you have multiple bands. If you want to show your image in red, set it to GCI_PaletteIndex and set a colortable.<br>
<br><div class="gmail_quote"><div><div class="h5">On Mon, Nov 28, 2011 at 6:40 AM, Graeme Merrall <span dir="ltr"><<a href="mailto:graeme@inetix.com.au" target="_blank">graeme@inetix.com.au</a>></span> wrote:<br></div>
</div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div class="h5">
<div>The smallest almost working code chunk I have right now is below. This is taaking a 40k by 40k and pulling out the top left quarter. The original has 4 bands - RGBA</div>
<div><br></div><div>
<div>from osgeo import gdal</div><div>import numpy</div><div>img = gdal.Open("original.tif")</div><div>geotransform = img.GetGeoTransform()</div><div>band1 = img.GetRasterBand(1)</div><div><br></div><div>driver = gdal.GetDriverByName("GTiff)</div>
<div># coordinates will be calculated but hardcoded for now</div><div>dst = driver.Create('sliver.tif', 20000, 20000, 1, gdal.GDT_Byte)</div><div>dst.SetProjection(img.GetProjection())</div><div>scanline1 = band1.ReadAsArray(0, 0, 20000, 20000)</div>
<div>dst.GetRasterBand(1).WriteArray(scanline1)</div><div><br></div><div>Should I be looping through each band and reading/writing to the image? I'm assuming yes</div><div><br></div><div>Also. band 1 of the original image is red but in the new image the band color is grey. I've tried a few variations with GDALRasterBand.SetColorInterpretation() with no luck. What have I missed?</div>
<div><br></div><div>Cheers,</div></div>
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<br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>
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