Changes between Version 5 and Version 6 of UserDocs/RasterProcTutorial

Timestamp:

Sep 24, 2007, 10:10:42 AM (17 years ago)

Author:

warmerdam

Comment:

add vrt and brief optimizing section.

UserDocs/RasterProcTutorial

@@ -286 +286 @@
 ----------
 
-... produce an optimized version of the previous mosaic. 
-
-ideally demonstrate effect using a mapfile and shp2img? 
+gdal_translate -co TILED=YES -co COMPRESS=DEFLATE mosaic4.tif tiled.tif
+
+gdaladdo tiled.tif 2 4 8 16 32 64
+
+Thats about it!
 
 
@@ -294 +296 @@
 -------------
 
+a) Create an example VRT with gdal_translate.
+
+   gdal_translate -of VRT east.dem east.vrt 
+
+   Inspect east.vrt, for instance with notepad.
+
+b) Skim VRT tutorial, available in Related Pages at www.gdal.org. 
+
+   Compare the elements of the tutorial to the elements of the file.
+
+c) Create VRT from geoworld.tif.
+  
+   gdal_translate -of VRT geoworld.tif 0to360.vrt
+
+d) Edit the <GeoTransform> tag and change:
+
+   -1.800000e+02 
+
+   to
+   
+   0.0
+
+   to set the origin to 0 longitude instead of -180 (the dateline).  Then
+   check the .vrt file with gdalinfo and OpenEV. 
+
+   gdalinfo 0to360.vrt
+   openev 0to360.vrt
+
+   Our extents are right, but the imagery is still wrong!
+
+e) Duplicate and modify this section:
+
+    <SimpleSource>
+      <SourceFilename relativeToVRT="1">geoworld.tif</SourceFilename>
+      <SourceBand>1</SourceBand>
+      <SrcRect xOff="0" yOff="0" xSize="2048" ySize="1024"/>
+      <DstRect xOff="0" yOff="0" xSize="2048" ySize="1024"/>
+    </SimpleSource>
+
+   to look like this:
+
+    <SimpleSource>
+      <SourceFilename relativeToVRT="1">geoworld.tif</SourceFilename>
+      <SourceBand>1</SourceBand>
+      <SrcRect xOff="0" yOff="0" xSize="1024" ySize="1024"/>
+      <DstRect xOff="1024" yOff="0" xSize="1024" ySize="1024"/>
+    </SimpleSource>
+    <SimpleSource>
+      <SourceFilename relativeToVRT="1">geoworld.tif</SourceFilename>
+      <SourceBand>1</SourceBand>
+      <SrcRect xOff="1024" yOff="0" xSize="1024" ySize="1024"/>
+      <DstRect xOff="0" yOff="0" xSize="1024" ySize="1024"/>
+    </SimpleSource>
+   
+  Check the result with openev ... now the hemispheres are appropriately
+  swapped!
+
+f) Now lets create an overlapping wrap world going from -180 to 360. 
+
+   gdal_translate -of VRT geoworld.tif overlap.vrt
+
+   Change rasterXSize from 2048 to 3072.
+
+   Leave GeoTransform unchanged.
+
+   Add this SimpleSource for the 180 to 360 portion.
+ 
+    <SimpleSource>
+      <SourceFilename relativeToVRT="1">geoworld.tif</SourceFilename>
+      <SourceBand>1</SourceBand>
+      <SrcRect xOff="0" yOff="0" xSize="1024" ySize="1024"/>
+      <DstRect xOff="2048" yOff="0" xSize="1024" ySize="1024"/>
+    </SimpleSource>
+   
+
+Python Scripting
+----------------
+
+Do a demonstration of reading east.dem into a  Numeric array, 
+setting all pixel values less than 1 to -100, and saving to a new 
+file. 
+
 }}}