OGR supports reading most versions of AutoCAD DXF and writing AutoCAD 2000 version files. DXF is an ASCII format used for interchanging AutoCAD drawings between different software packages. The entire contents of the file is represented as a single layer named "entities".

DXF files are considered to have no georeferencing information through OGR. Features will all have the following generic attributes:

Supported Elements

The following element types are supported:

A reasonable attempt is made to preserve line color, line width, text size and orientation via OGR feature styling information when translating elements. Currently no effort is made to preserve fill styles or complex line style attributes.

The approximation of arcs, ellipses, circles and rounded polylines as linestrings is done by splitting the arcs into subarcs of no more than a threshhold angle. This angle is the OGR_ARC_STEPSIZE. This defaults to four degrees, but may be overridden by setting the configuration variable OGR_ARC_STEPSIZE.


The default behavior is for INSERT entities to be expanded with the geometry of the BLOCK they reference. However, if the DXF_INLINE_BLOCKS configuration option is set to the value FALSE, then the behavior is different as described here. The intention is that with DXF_INLINE_BLOCKS disabled, the block references will remain as references and the original block definitions will be available via the blocks layer. On export this configuration will result in the creation of similar blocks.

Character Encodings

Normally DXF files are in the ANSI_1252 / Win1252 encoding. GDAL/OGR attempts to translate this to UTF-8 when reading and back into ANSI_1252 when writing. DXF files can also have a header field ($DWGCODEPAGE) indicating the encoding of the file. In GDAL 1.8.x and earlier this was ignored but from GDAL 1.9.0 and later an attempt is made to use this to recode other code pages to UTF-8. Whether this works will depend on the code page naming and whether GDAL/OGR is built against the iconv library for character recoding.

In some cases the $DWGCODEPAGE setting in a DXF file will be wrong, or unrecognised by OGR. It could be edited manually, or the DXF_ENCODING configuration variable can be used to override what id will be used by OGR in transcoding. The value of DXF_ENCODING should be an encoding name supported by CPLRecode() (ie. an iconv name), not a DXF $DWGCODEPAGE name. Using a DXF_ENCODING name of "UTF-8" will avoid any attempt to recode the text as it is read.

Creation Issues

DXF files are written in AutoCAD 2000 format. A standard header (everything up to the ENTITIES keyword) is written from the $GDAL_DATA/header.dxf file, and the $GDAL_DATA/trailer.dxf file is added after the entities. Only one layer can be created on the output file.

Point features with LABEL styling are written as MTEXT entities based on the styling information.

Point features without LABEL styling are written as POINT entities.

LineString, MultiLineString, Polygon and MultiPolygons are written as one or more LWPOLYLINE entities, closed in the case of polygon rings. An effort is made to preserve line width and color.

The dataset creation supports the following dataset creation options:

Note that in GDAL 1.8 and later, the header and trailer templates can be complete DXF files. The driver will scan them and only extract the needed portions (portion before or after the ENTITIES section).

Block References

It is possible to export a "blocks" layer to DXF in addition to the "entities" layer in order to produce actual DXF BLOCKs definitions in the output file. It is also possible to write INSERT entities if a block name is provided for an entity. To make this work the follow conditions apply. The intention is that a simple translation from DXF to with DXF_INLINE_BLOCKS set to FALSE will approximately reproduce the original blocks and keep INSERT entities as INSERT entities rather than exploding them.

Layer Definitions

When writing entities, if populated the Layer field is used to set the written entities layer. If the layer is not already defined in the template header then a new layer definition will be introduced, copied from the definition of the default layer ("0").

Line Type Definitions

When writing LWPOLYLINE entities the following rules apply with regard to Linetype definitions.

The intention is that "dot dash" style patterns will be preserved when written to DXF and that specific linetypes can be predefined in the header template, and referenced using the Linetype field if desired.