Overview
Several image formats are supported by MDNS: BMP, GIF, PNG and JPEG. Supported image formats apply to two areas of the product: map and legend icon rendering and map image post-processing (
overlays and
clipping).
Supported Formats
Only a subset of the supported formats in your
MapFile are also supported in MDNS. The common supported set are defined using a syntax as exemplified here: (these definitions describe the final output version of your requested image)
OUTPUTFORMAT
NAME gif
DRIVER "GD/GIF"
MIMETYPE "image/gif"
EXTENSION "gif"
END
OUTPUTFORMAT
NAME png
DRIVER "GD/PNG"
MIMETYPE "image/png"
EXTENSION "png"
END
OUTPUTFORMAT
NAME jpeg
DRIVER "GD/JPEG"
MIMETYPE "image/jpeg"
EXTENSION "jpg"
END
OUTPUTFORMAT
NAME wbmp
DRIVER "GD/WBMP"
MIMETYPE "image/wbmp"
EXTENSION "wbmp"
END
Map Rendering
The
MapService is responsible for rendering map and legend icon images. If during a map rendering you request either clipping or overlay support, then the map image is automatically converted internally to a 32bpp ARGB. The image is then down-converted to whatever output format you have selected.
note: if you have a watermark because you are using a non-production license, then overlays are in use
note: anti-aliasing requires a non-paletted format (like PNG32)
Virtual Earth Formats for Tile Overlays
Best Practices
1. If you intend to use the clipping or overlay feature of a
MapRequest - use JPEG if possible as your final output
2. If you are not using any post-processing then use PNG as it's quality is excellent and compression efficient
3. If you intend to use tile overlays for Virtual Earth and you need a transparency color - use PNG
4. If you intend to not use a transparency color but instead use VE opacity on the tile specification - use a JPEG
5. Avoid using GIF if you intend to use the clipping or overlay feature - GDI+ has a poor-looking quantization routine
MDNS Web Services web.config<add key="ImageQuality" value="75"/> - sets the compression level on the jpeg format