Importing Images

Import images into Manifold using the File - Import - Image dialog. In addition, images stored within databases using spatial DBMS technology can be imported by connecting to the database using Database Console, clicking on the image to highlight it and then clicking the Import button in the Database Console toolbar.

When using the File - Import - Image dialog the Files of type choice acts as a filter for what is displayed in the browse pane in the Import dialog. Simple file types are imported directly from the Import dialog by choosing the desired type in the Files of type box. More complex imports from data sources such as databases are imported by choosing Data Sources () in the Files of type box and then using the Data Source dialog.

Formats used to save drawings vary widely in their capabilities. Some formats save projection information and some, such as .dxf or many types of .shp files, do not. When a drawing format contains projection information, Manifold will automatically use that projection information.

Formats that do not preserve projection information (the majority) will require manual intervention to place and scale the image correctly within a geographic context. Most often the image will be placed in a geographic context through georegistration .

Note: USGS DOQ files as provided on CDs are normally not georegistered. Most often these are .jpg format files created from the original DOQ format files and provided on CD without the .jpg extension.

See the Projections and Images topic for an introduction to projection issues involving images.

Importing Satellite Image Formats

Many formats used for satellite images are located under File - Import - Surface because such formats are often used to present non-visual data as raster data sets. See the Importing Surfaces topic.

For example, HDF, HDF EOS and HDF SeaWiFS formats are found in the File - Import - Surface dialogs. If you don't see a desired format listed in the image importers, check under surfaces.

When importing HDF files, use HDF SeaWiFS for SeaWiFS data in .hdf format and use HDF EOS for Earth Observation Satellite data in .hdf format. While the ordinary HDF converter will also import some data from HDF SeaWiFS files it will ignore multidimensional data chunks (called Scientific Data Sets or SDSs) that are used to contain pixels. Note also there is a CEOS SeaWiFS importer for data in that form.

Some file types, such as ENVI, ERDAS and ERS (ECW) files, can contain either surface or image data, depending on how the data is intended to be interpreted. The ENVI, ERDAS and ERS (ECW) importers occur both in the File - Import - Surface and File - Import - Image menus and have a subtype option to allow specification of image or surface upon import.

Importing Georegistered Images

The preferred format for importing georegistered images is GeoTIFF format. This standard is supported by over 150 companies and provides for reliable import of images with correct georegistration. Some other formats, such as ECW can also save projection information.

Use of World Files

An obsolete way of providing partial projection information for images is the use of "world" files. World files do not contain the name of the projection used. They simply provide certain local projection values and leave it up to the user to manually specify the actual projection in use. A world file is a small text file that accompanies the image file. For example, an image called Europe.jpg that is an ordinary graphics file in JPG format might be accompanied by a small file called Europe.jpgw, which is the world file. The Europe.jpgw file is an ordinary ASCII text file containing a few lines of text. The extension ".jpgw" is used to let GIS software know that it is a world file.

If we opened up the Europe.jpgw world files in Notepad we would see something like the following:

4.000000

0.000000

0.000000

-4.000000

574400.000000

4145600.000000

The numbers provide information on local offset and local scale for whatever projection is in use. However, the world file does not actually say what projection has been used. When publishing images accompanied by world files the assumption is that the user knows what projection is supposed to be used and is capable of manually specifying it in the GIS software being used.

This is a really stupid system, of course, since the moment images are distributed away from their author and other people who know the secret of what projection was used there is nothing in the world file to tell the rest of normal humanity what the author intended. If you are using images accompanied by world files, it is critically important to search carefully through the website from which you downloaded the images to find any information that describes what projection was used. If you cannot find a file or web page that specifies the actual projection that was used the world file alone will not help you georegister the image.

Once you know the projection you can georegister images accompanied by world files by adding the local projection parameters they specify to the projection in use. Manifold makes this easier by automatically reading the local projection information from a world file that accompanies an image file. When loading images from TIF, BMP, GIF, JPG, PCX, PNG and TGA formats, Manifold scans the directory to see if there is a similarly named file having one of the two common world file extensions. If so, Manifold opens the world file and loads the local projection information from the world file.

For TIF, BMP, GIF, JPG, PCX, PNG and TGA formats the world file extensions are usually in the form .tifw, .bmpw, .gifw, .jpgw, .pcxw, .pngw and .tgaw respectively; however, some world files may have extensions in the form .tfw, .bpw, .gfw, .jgw, .pxw, .pgw and .taw respectively. Manifold will automatically read world files having either the ".tifw" or ".tfw" style of filename extension.

Once the image has been imported, it must be opened and the Edit - Assign Projection dialog must be used to specify the correct projection. See the Download and Mosaic Terraserver Images topic for an example of this process using world files and images.

Typical Image Formats

Manifold can import from many different image formats. Some are highly specialized formats that provide much data organized in a complex way. Precise description of certain specialty formats is beyond the scope of this document. In such cases, please refer to the originating agency or company for detailed documentation on their format.

Interested in support for a new format not listed below? See the Contacting manifold.net topic for information on suggesting a new format.

Searching Internet with a good search engine will find numerous references to format documentation as well. For example, searching for "PNG" and "Portable Network Graphics format" on Google turns up the PNG home page as the first hit.

XML Files Created upon Export and Used on Import

Not all formats to which Manifold can export have the ability to correctly save projection information. As a safety measure to ensure that projection information is never lost, Manifold always writes an accompanying .xml file when exporting drawings, images, labels, maps or surface components to a file. The accompanying .xml file contains coordinate system information and some other metadata. The XML file is created for all formats, even those that correctly save coordinate system information.

When Manifold imports drawings, images, labels or surfaces, the system will check for an accompanying .xml file that might have been written by Manifold. If such an .xml file exists, Manifold will read it and use the information it contains to load a correct coordinate system.

See the XML Accessory File Format topic for details on the internal organization of this file.

Imported or Linked Images from Tables or Queries

Manifold can import images or link images from information stored in tables or provided by queries by using the Data Source dialog. The tables and queries used to create linked images may be inside the Manifold project or they may be in external databases.

Linked images may also be created in a two step process, where the virtual table for an existing image is used in a query to manipulate that image or to fetch part of the image based upon desired criteria. A linked image can then be created from that query. This technique is often used within Manifold projects that will be used in an IMS website.

Linked images may also be created from tables or queries stored in external databases. For example, we could use a query to select all columns for all pixels in an image's virtual table and then export that query as a table into an .mdb file or to some other database storage.

When an image is linked from a table or query, each record in the table or query produces a pixel. The coordinates of the pixel are taken from the X and Y columns (cast to integer) specified in the Link dialog. The color of the pixel is taken from either the Color column or the channel columns.

If you have Manifold System Enterprise Edition or greater you can also import images or link images from Oracle data sources that use Oracle's Spatial or Locator technologies. Importing images from Oracle data sources is virtually identical to linking them from Oracle data sources. See the Linked Images from Oracle Servers topic.

Importing or linking images from databases is normally accomplished using the Database Console to connect to the DBMS, and then the Import or Link Database Console toolbar button is used to import or link the desired image from the database.

Importing Images from Image Servers

In addition to the straight File - Import - Image importers within Manifold we can also import images by first creating a linked image that is dynamically fetched from an image server and then unlinking or downloading that linked image to create a local image. This allows us to import images covering a desired area from image servers. See the Linked Images topic to learn more about linked images and image servers.

Important Note when Using 64-bit Manifold Editions

Due to a lack of required Microsoft facilities in 64-bit Windows systems, Manifold in 64-bit mode cannot export, import, export or link to DB, HTML, MDB, XLS or WKx format files. This includes no access to the MDB parts of Manifold MFD and MapInfo TAB imports. The workaround for importing or exporting such files is to launch Manifold in 32-bit mode by using the Manifold System (32-bit) shortcut, perform the export from or import into a .map project file and then re-launch Manifold in 64-bit mode using the Manifold System (64-bit) shortcut. Linking is more complex: the data must be in some format usable in 64-bit mode within 64-bit Windows systems, such as a SQL Server database. Alternatively, the data can be kept within a Manifold .map project file and linked using the Manifold ODBC driver.

See Also

Projections and Images

Images and subsequent topics.

Georegistration and subsequent topics.

Historical Notes

Some graphics formats popular with the graphics communities arise from formerly elite machines used before PCs redefined the meaning of "elite." In case the companies involved are gone or forgotten by the time this is read, a few notes for younger readers:

SGI was an elite graphics company in Mountain View that ended up as a sort-of UNIX workstation vendor famous for three things: 1) Inventing OpenGL, 2) Having a very cool building across the street from the Century 16 cineplex in Mountain View that now, appropriately enough, serves as a museum of computer technology, and 3) Last, but not least, failing to keep up with the price/performance competition of Wintel clones running cool new graphics engines from companies like NVIDIA.

SUN once was an elite UNIX workstation company in Palo Alto before clones banished it to a netherworld existence as a server appliance company. Sun was yet another company that started with a plug-in graphics card, a Multibus card for the "Stanford University Network" (SUN) machines then in use at Stanford. They went on to bigger and better things, including a respectable workstation and server business. Unfortunately, they were run over by the steamroller of high power / low cost clones running ever more applications-rich Windows operating systems, and "workstation" became just another synonym for "PC."

AT&T at one point was the fearsome owner of all telecommunications mojo in the US. They also (we're not making this up) built a "high performance" graphics card called the Targa that plugged into PCs. The AT&T brand lives on as a new identity for one of the "baby Bells" that ended up consuming the parent and is now busy gobbling up cell phone companies.