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Subject: RE: [cgmo-webcgm] POLL ISSUE: zero-valued LINE WIDTH, stroke weight
1a and 2a, then reopen the discussion for 2.1 (see Lofton's comments). For the past 13 years I have had the question from customers why the CGM world is not capable of changing the standard such that a simple thing like a no-stroke line becomes possible. NOTE: These are cases where no stroke is intentional. The cases Forrest is referring to are probably degenerate cases, where CGM writers relied on the recipient to handle degenerate cases well. > -----Original Message----- > From: Cruikshank, David W [mailto:david.w.cruikshank@boeing.com] > Sent: Friday, June 10, 2005 10:18 PM > To: CGM Open WebCGM TC > Subject: [cgmo-webcgm] POLL ISSUE: zero-valued LINE WIDTH, stroke weight > > > All, > > I've read through the thread on this one and will summarize. > > There are two questions here and everyone needs to answer them > independently. > > 1) What should WebCGM say about the treatment of zero width > lines (line width specifier of 0 value on the Line Width > attribute element in CGM)? > a) Leave it as it is specified in WebCGM? > b) Change the meaning of a zero value to mean "no stroke"? > Recommendation a) > > 2) What should WebCGM say about the allowable values and > treatment of the stroke weight style property of WebCGM set > through the DOM? > a) Limit value of both NVCC and relative scale to >0? > b) Allow zero values for both NVDC and relative scale and > adopt CGM conventions? > c) Allow zero values for both NVDC and relative scale and > define the meaning as "no stroke"? > Recommendation a) > > Summaries > > 1) The CGM standards allows for parameter values for the line > width specifier of the Line Width attribute element to be > non-negative. That means the Line Width can be set to zero in > CGM. In the "informative" guideline for interpreters in Annex D, > the CGM standard recommends: "If a zero size is specified in the > metafile, it is recommended that interpreters select the minimum > available size for affected primitives." Currently in the WebCGM > 2.0 Profile (T20.3), the meaning of a zero value is "Minimum > available line width". > > 2) Currently the WebCGM 2.0 DOM chapter has a restriction of the > allowable values for stroke width. It limits the relative scale > stroke width to >0%, but doesn't address absolute NVDC as far as > I can tell. > > Personal thoughts > > >From a user standpont we have had a requirement for a "line > visibility" element in CGM similar to Edge Visibility, but I > think that is something that should be addressed at the CGM > standard level and not in the profile. > > thx...Dave Cruikshank > > Technical Fellow - Graphics/Digital Data Interchange > Boeing Commercial Airplane > 206.544.8876, fax 206.544.9590 > david.w.cruikshank@boeing.com > >
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