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<html><head><title>Microstation DGN</title></head><body bgcolor="#ffffff"><h1>Microstation DGN</h1>Microstation DGN files from Microstation versions predating version 8.0are supported for reading. The entire file is represented as one layer(named "elements").<p>DGN files are considered to have no georeferencing information through OGR. Features will all have the following generic attributes:<ul><li> Type: The integer type code as listed below in supported elements. <li> Level: The DGN level number (0-63). <li> GraphicGroup: The graphic group number.<li> ColorIndex: The color index from the dgn palette.<li> Weight: The drawing weight (thickness) for the element. <li> Style: The style value for the element. </ul>DGN files do not contain spatial indexes; however, the DGN driver does takeadvantage of the extents information at the beginning of each element to minimize processing of elements outside the current spatial filter windowwhen in effect.<p><h2>Supported Elements</h2>The following element types are supported:<p><ul><li> Line (3): Line geometry. <li> Line String (4): Multi segment line geometry.<li> Shape (6): Polygon geometry. <li> Curve (11): Approximated as a line geometry.<li> B-Spline (21): Treated (inaccurately) as a line geometry.<li> Arc (16): Approximated as a line geometry.<li> Ellipse (15): Approximated as a line geometry.<li> Text (17): Treated as a point geometry.</ul>Generally speaking any concept of complex objects, and cells as associatedcomponents is lost. Each component of a complex object or cell is treatedas a independent feature.<p><h2>Styling Information</h2>Some drawing information about features can be extracted from the ColorIndex,Weight and Style generic attributes; however, for all features an OGRstyle string has been prepared with the values encoded in ready-to-use formfor applications supporting OGR style strings.<p>The various kinds of linear geomtries will carry style information indicatingthe color, thickness and line style (ie. dotted, solid, etc).<p>Polygons (Shape elements) will carry styling information for the edge as well as a fill color if provided. Fill patterns are not supported.<p>Text elements will contain the text, angle, color and size information (expressed in ground units) in the style string.<p><h2>Creation Issues</h2>2D DGN files may be written with OGR with significant limitations:<P><ul><li> Output features have the usual fixed DGN attributes. Attempts to createany other fields will fail.<p><li> Virtual no effort is currently made to translate OGR feature stylestrings back into DGN representation information. <p><li> POINT geometries that are not text (Text is NULL, and the featurestyle string is not a LABEL) will be translated as a degenerate (0 length)line element. <p><li> Polygon, and multipolygon objects will be translated to simple polygonswith all rings other than the first discarded.<p><li> Polygons and line strings with too many vertices will be split into a group of elmements prefixed with a Complex Shape Header or Complex ChainHeader element as appropriate. <p><li> A seed file must be provided (or if not provided, $PREFIX/share/gdal/seed_2d.dgn will be used). Many aspects of the resultingDGN file are determined by the seed file, and cannot be affected via OGR, such as initial view window. <p><li> The various collection geometries other than MultiPolygon are completelydiscarded at this time. <p><li> Geometries which fall outside the "design plane" of the seed file willbe discarded, or corrupted in unpredictable ways.<p><li> DGN files can only have one layer. Attemptsto create more than one layer in a DGN file will fail.<p></ul>The dataset creation supports the following options:<p><ul><li> <b>3D=</b><i>YES</i> or <i>NO</i>: Determine whether 2D (seed_2d.dgn) or 3D (seed_3d.dgn) seed file should be used. This option is ignored if the SEED option is provided.<p><li> <b>SEED=</b><i>filename</i>: Override the seed file to use.<p><li> <b>COPY_WHOLE_SEED_FILE=</b><i>YES/NO</i>: Indicate whether the wholeseed file should be copied. If not, only the first three elements (and potentially the color table) will be copied. Default is NO.<p><li> <b>COPY_SEED_FILE_COLOR_TABLEE=</b><i>YES/NO</i>: Indicates whether thecolor table should be copied from the seed file. By default this is NO. <p><li> <b>MASTER_UNIT_NAME=</b><i>name</i>: Override the master unit name fromthe seed file with the provided one or two character unit name. <p><li> <b>SUB_UNIT_NAME=</b><i>name</i>: Override the sub unit name fromthe seed file with the provided one or two character unit name. <p><li> <b>SUB_UNITS_PER_MASTER_UNIT=</b><i>count</i>: Override the number ofsubunits per master unit. By default the seed file value is used.<p><li> <b>UOR_PER_SUB_UNIT=</b><i>count</i>: Override the number ofUORs (Units of Resolution) per sub unit. By default the seed file value is used.<p><li> <b>ORIGIN</b>=<i>x,y,z</i>: Override the origin of the design plane. Bydefault the origin from the seed file is used.<p></ul><hr><ul><li> <a href="http://dgnlib.maptools.org/">Dgnlib Page</a><li> <a href="http://home.gdal.org/projects/opengis/ogr_feature_style.html">OGR Feature Style Specification</a></ul></body></html>⌨️ 快捷键说明
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