Changes between Version 26 and Version 27 of MapGuideRfc51

Timestamp:

Nov 14, 2008, 1:17:19 PM (15 years ago)

Author:

tonyfang

Comment:

--

MapGuideRfc51

@@ -121 +121 @@
 
 Upon further investigation, it is not correct to shift the image when the re-projection is a datum shift. Transformations are not that simple. The advanced algorithm will be invoked for all CS transformations.
+
+--------
+
+If the RasterGridSize is close in size to the actual width or height of your image (e.g. a RasterGridSize that is ~50% of the height/width), and the raster re-projection is more than a simple affine transformation (e.g. LL84 -> World-Sinusoidal), then you will end up with a poor raster re-projection.
+
+One place you will commonly encounter this situation is with the Fusion Overview Map. This may also occur when your window size is very small.
+
+To address this, a few more configuration settings will be added to the serverconfig.ini. In addition to RasterGridSize, we will also add MinimumRasterGridSize and RasterGridSizeOverrideRatio.
+
+{{{
+[RenderingServiceProperties]
+# *****************************************************************************
+# R E N D E R I N G  S E R V I C E
+#
+# Property Name                    Description
+# -----------------------------------------------------------------------------
+# RasterGridSize                   Size of raster re-projection grid in pixels
+# MinimumRasterGridSize            Minimum size of raster re-projection grid in 
+#                                  pixels. This must be less than RasterGridSize.
+# RasterGridSizeOverrideRatio      If the RasterGridSize is larger than the 
+#                                  image's height or width times the 
+#                                  RasterGridSizeOverrideRatio, then the 
+#                                  RasterGridSize is overridden with this value.
+#                                  Change this setting to 1 to disable the
+#                                  override.
+# *****************************************************************************
+RasterGridSize                     = 100
+MinimumRasterGridSize              = 10
+RasterGridSizeOverrideRatio        = 0.25
+}}}
+
+First we check to see if the RasterGridSize needs to be overridden. i.e., Is RasterGridSize less than 25% of the height/width of the image? 
+Then we check to see if the RasterGridSize is at least the minimum. i.e., Is RasterGridSize greater than 10?
+Then we check to see if the RasterGridSize is less than the height/width of the image.
+
+The following examples will help illustrate how the three settings interact with each other.
+
+All examples use the following (default) values:
+RasterGridSize                     = 100
+MinimumRasterGridSize              = 10
+RasterGridSizeOverrideRatio        = 0.25
+
+Example 1:
+If you have a request that re-projects a 100x150 image, the RasterGridSize would get reduced to 25 pixels.
+
+Example 2:
+If you have a request that re-projects a 30x30 image, the RasterGridSize would get reduced to 10 pixels.
+
+Example 3:
+If you have a request that re-projects a 600x600 image, the RasterGridSize stays at 100 pixels.
+
+Example 4:
+If you have a request that re-projects a 5x5 image, the RasterGridSize would get reduced to 5 pixels. 
+