Matthieu,<br><br>Looks like you are finally reprojecting the image, perhaps to the projection of image B. Reprojection is costly. I suggest performing it on A instead of B. Let us know how it goes.<br><br><div class="gmail_quote">
On Wed, May 12, 2010 at 7:19 PM, Matthieu Rigal <span dir="ltr"><<a href="mailto:rigal@rapideye.de">rigal@rapideye.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi folks,<br>
<br>
I am currently implementing a tool to allow band-to-band computations on<br>
array values out of 2 images with different projection and different<br>
resolution in python.<br>
<br>
The operation is quite complex, so I will summarize it here and below give<br>
the solution I am currently testing to see if it is the best one and ask<br>
for some enhancements and performance hints. Unfortunately, the high-level<br>
warping class is, at my knowledge, only available in C++.<br>
<br>
Workflow (could also be improved by all-in-one functions like for C++)<br>
- Open image A, 5000*5000 pixels, 5m resolution, UTM<br>
- Open image B, approx 100m resolution, LatLon, much larger than the<br>
previous one<br>
- Cut out the buffered extents of image A from image B<br>
- Reproject this cutted image to the projection and resolution of image A<br>
- Read full image A as array<br>
- Read extents of image A from image B as array<br>
<br>
It sounds easy, but when I started implementing it, I figured out that it<br>
was quite complicated and that it would be quite time consuming, so if you<br>
have any suggestions, this is my pseudo-code (I thought about writing a<br>
real code, but it may be too long for the list, if I want to also include<br>
the generation of image A and B at the beginning):<br>
- gdal.Open(imgA, imgB)<br>
- GetGeoTransform(imgA, imgB)<br>
- CreateGeometry(boundaries of imgA).Buffer<br>
- Transform(projection imgB)<br>
- GetEnvelope(transformed geometry)<br>
- transform to in-image of imgB x, y, x_off, y_off<br>
- Create new image in memory<br>
- Calculate its geotransform<br>
- Read the bands into memory (GetRasterBand().Read and .Write() or<br>
ReadIO() ?)<br>
- Reproject the image<br>
- Get GeoTransform<br>
- Calculate in-image coordinates to finally read exactly the same window as<br>
array<br>
<br>
Best Regards,<br>
Matthieu<br>
<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9848167848<br>17.2416N 80.1426E<br>