2. Overview of CGM CGM is a binary vector graphics format.
Primarily used in technical graphics
Most are generated from CAD source
Allows for embedded images
ISO/IEC 8632:1999 Standard
WebCGM profile is a W3C recommendation
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3. Reasons for Conversion
Interoperability
XML based graphics
Functionality
Dynamic capabilities
Reusability
SVG Fragments
Isolate changes
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4. File Size Using the ATA/NIST test suites CGM SVG SVGZ 6.38mb 30.1mb
Files were all converted using Quick.SVG.
There were just under 300 files in the suite.
CGM
SVG
SVGZ
6.38mb
30.1mb
4.4mb
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5. Issues
SVG does not support bounding box for <text/> or <tspan/> elements
Restricted Text
We can not use the textLength attribute because it is not well
supported by viewers.
The solution is to apply SVG transformation to text element to
yield appropriate size.
<g transform="scale(1.8 1)">
<text x=“0” y=“0”>Restricted Text</text>
</g>
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6. Issues CGM coordinate system can be inverted X axis, Y axis, or both.
SVG
It is best to detect inversions in CGM and translate all coordinates to place the origin at the top left of the screen.
Since you will be touching all coordinates you can take this opportunity to apply any operations such as scaling to the CGM data.
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7. Issues Splines CGM supports non-uniform b-splines
The curve could of course be constructed from polylines at varying precisions with very low resource usage.
The better solution is to approximate bezier curves to the spline. This can be done with near zero loss and moderate resource usage.
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8. Issues
Figures
SVG has no simple translation from the CGM figure element
CGM
<Figure>
<Graphical-Element/>
<Edge Visibility=“True”/>
<Graphical-Element />
<New-Region/>
<Figure/>
CGM
SVG translating the figure directly with path element
SVG translating the figure directly with path element
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9. Other Issues Emulating multi-link in SVG Engineering line types
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