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All Blog Articles, Data Models and Free Source Code by Simon Greener, The SpatialDB Advisor is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Image Catalog Tool

Monday August 21 2006 at 20:40

The header from the ImageCatalog script within the imagecatalog.map file is:

’ @application: ImageCatalog
’ @precis     : A general purpose tool for working with ESRI-style image catalogs. Similar to
’               Microsoft TerraServer’s TerraCutter application.
’ @version    : 3.0
’ @description: ESRI Image Catalogs are a method for organising large numbers of images
’               under a single structure that can be used as a single “theme” in a mapping application.
’
’               Generally, these Image Catalogs are simple and are based on a DBF (or INFO) table
’               whose attributes are:
’
’               IMAGE – String – Full path name to the actual image file eg c:\myimages\col234\c234r123.tif
’               XMIN  – Number – X ordinate of Lower Left (LL) corner of the image in real world coordinate system.
’               YMIN  – Number – Y ordinate of LL corner of image in real world coordinate system.
’               XMAX  – Number – X ordinate of Upper Right (UR) corner of the image in real world coordinate system.
’               YMAX  – Number – Y ordinate of UR corner of image in real world coordinate system.
’
’               This attribute file-base approach does have shortcomings. For example, it is not possible to 
’               “visualise” tile boundaries as vector objects. Nor is it easy to see the “extent” 
’               of the image catalog. 
’
’               Another limitation of ESRI Image Catalogs is that they do not require that the individual 
’               images that it references be non-overlapping. They provide no logical metadata to
’               control tile creation or organisation. 
’
’               Constructing Image Catalogs is tedious and requires specialist software: Manifold
’               provides all the required functionality to construct individual images but does not 
’               have the higher level “framework” or “ease of use” tools for constructing actual
’               image catalogs. 
’
’               This Image Catalog application addresses all these issues as follows:
’
’               1. Individual Image Catalogs are hosted as Drawings and exported to disk as
’                  shapefiles whose DBF files contain the ESRI attributes.
’                  The approach taken here is similar to UNC’s MapServer: image catalogs constructed
’                  using this tool should work within MapServer.
’               2. An additional shapefile – called the boundary shapefile – is maintained which only 
’                  shows the outer extent of the tiles in the image catalog: this is useful in mapping 
’                  applications where one shows the boundary at small scales and only shows the image 
’                  tiles themselves at larger scales.
’               3. Any single image catalog is defined as a logical grid (like a matrix) over a
’                  particular piece of geographic space. Each tile or cell in the grid has a predefined
’                  size in X and Y. The logical grid is “sparse” in that cells are not created unless
’                  a tile exists in that logcal. 
’               4. The size information is used to construct a logical address for each cell as a col/row address.
’                  The images resulting from each each tile are organised on disk into a hierarchical
’                  folder structure in which folders are created for each logical column and all row tiles
’                  in that column are stored in that folder.
’                  This is done to minimise directory search problems which result in most operating systems
’                  when the number of files in a directory become too large. This is still fairly coarse and
’                  could be refined so that the rows were themselves organised perhaps into Base16,32 or 64 buckets.
’                  Another improvement would be for the images to be organised by a Peano, Morton or 
’                  some other space curve key (this would help in DBMS based image catalogs by creating a single
’                  searchable primary key column).
’               5. An image catalog has attached projection information.
’               6. An image catalog has a defined minimum precision of the pixels in each tile’s image in X and Y.
’                  New images to be inserted into a catalog can have better precision but images with worse
’                  precision are resampled to that pixel size IF the user requests. Otherwise they are ignored.
’               7. Image catalog metadata is managed by a CatalogRegistry table (stored on disk as a DBF file).
’
’               To minimise the number of disk files all images are stored on disk as GeoTiffs. All
’               Manifold XML files are removed after each image has been exported to disk. The XML
’               is superfluous as the projection information is a fundamental part of the image catalog’s
’               metadata.
’
’               New images to be inserted into a catalog are processed as follows:
’
’               1. The logical tiles that overlay the image are constructed in the projected space
’                  of the image catalog.
’               2. Each tile is then processed (via 2 nested for loops).
’               3. Image creation:
’                  A. If an image already exists in the original image catalog it is loaded.
’                  B. If an image exists in the output “changes” directory (see later) it is
’                     loaded in preference to A.
’                  C. If neither A nor B apply a new image component is created.
’               4. A Query is constructed to select those pixels in the source image that
’                  pertain to the new image (with sufficient overlap).
’               5. The selected pixels (if non the tile is skipped) are then copied and pasted
’                  to the image component representing the tile. Note: missing pixels will not
’                  over-write existing pixels. If the selection is of one colour it is skipped if the 
’                  user ticks the appropriate box.
’               6. The image is written to disk and an entry placed in the image catalog’s drawing
’                  if a new tile had to be created.
’               
’               When all tiles and images have been processed the image catalog drawing is written
’               to disk and any related Boundary shapefile updated via an import, update UnionALL query,
’               and export process.
’ @usage      : Simply select the ImageCatalogTool component and run. Follow the Tab boxes to set up
’               the required processes and execute.
’ @requires   : The following options are required when running this script:
’               * Fill new pixels with current colour  –  Off
’               * Import data to separate folders – Off
’               * Import empty columns in tables – On
’               * Confirm expanding images or surfaces when pasting – Off
’ @return     : Nothing.
’ @tobedone   : Mosaic a selection of tiles in an Image Catalog.
’ @history    : Simon Greener – 2003 – Converted from ArcInfo AML and Avenue.
’               Simon Greener – 2004 – Numerous fixes.
’               Simon Greener – Jan 2005 – Totally re-wrote using VBScript Classes. Also took advantage of new Query capabilities in 6.00 SP1.
’               Simon Greener – Apr 2005 – Fixed bugs and improved performance using new 6.5 features.
’               Simon Greener – Sep 2005 – Added in support for CSPreset and Allows for CatalogRegistry component to already exist.
’                                        – Support for Logos in folder not being detected as images to tile
’ @History    : Simon Greener – Oct 2005 – Added support for history shapefile
’ @History    : Simon Greener – Jan 2006 – Support for image catalogs being NON-updateable if its CatalogRegistry.OutImgFldr is empty
’                                        – Modified handling of image coordinate system parameters (bug fix).
’                                        – Added in “Remove Projection (XML) capability”
’ @history    : Simon Greener – Feb 2006 – Support for user definable image folder prefixes
’                                        – Support for CatalogRegistry based RemoveXML, Resample, ESRIWorld, Image Format, Compressions and Options
’                                        – Support for resampling existing tiles if pixelsize > desirable pixel size
’                                        – Added in Mosaicing from Catalog and Components
’                                        – Removed create catalog records only and tile from catalog records options.
’                                        – Integrated Jamie Keene’s work wherein a selection that contains a single colour is ignored (using flag)

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