Apache OpenOffice (AOO) Bugzilla – Issue 12391
Provide true bezier clipping support or fake it where impossible
Last modified: 2013-02-07 22:17:49 UTC
When converting curves to polygons, the approximation is fairly poor due to too few interpolation points, and visible to the naked eye. This is a problem especially when exporting to EPS, where circles and ellipses obtain a visibly jagged look.
I have tested this in current version 1.0.2 and had no problems. Would it be possible to attach a screenshot and a document where the problem is visible? Thanks in advance.
Please see the attachment. It includes a .sxd file of an ellipse converted to a polygon (created with OOo 1.1beta), a .png screenshot, and a .pdf file obtained by printing the converted ellipose to a PDF converter (Aladdin Ghostscript 8.00). Most critical is that the jaggedness of the conversion is visible when printing to a printer. I'm happy to observe that Export to EPS doesn't seem to implicitly convert curves to polygons anymore in the 1.1 beta (Export to WMF still does). However, various other functions do (the shape functions for good reasons, but Connect and Combine inexplicably convert curves to polygons, too), so the printing quality should be solid (or at least settable).
Created attachment 5244 [details] .tar.gz file with example files.
Set to new.
Reassigned to Armin. This is reproduceable in version 1.0.2 and in a current internal one. Please have a look if there is something to be done about this . Thanks.
AW->THB: This seems to be a candidate for OOo 2.0 or OOo later. We are working on overhauling all the curve handling (and have started in some parts for 1.1).
This bug has various aspects, I'll try to explain them one by one (please add anything I might have missed): 1. Shape conversion to polygon always yields a line polygon 2. Some export filter convert even polygons containing beziers to line polygons 3. Polygon-polygon munging always results in line polygons Item 1 is maybe a problem of terminology. The term "Polygon" at the UI level implies line polygon. If one converts an ellipse to "Curve", beziers are preserved. Nevertheless, a "Curve" is a polygon just the same, and can be used with Combine/Connect/whatever. Item 2 is based on the fact that formats like WMF simply do not support curves at all. If you encounter exporters whose target format does provide curves (like EPS or EMF), please file a bug then. Item 3 is the real bug (or missing feature, as I prefer to call it), as you cannot currently perform the shape algebra with true curves. As Armin said, this is a planned feature for 2.0, we'll have to have a working bezier clipping algorithm for that.
Actually, while all that additional functionality would be nice, my main concern (and why I labeled it as a defect, and not an enhancement request) is that if I _want_ to convert a curve to a polygon (and I mean a polygon, and not a sequence of bezier segments), the approximation is poor. The underlying problem seems to be that conversion (whether to polygons, or to bitmaps) occurs based on screen resolution, and not based on any resolution that you want to print at.
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"According to the OpenOffice.org roadmap (http://tools.openoffice.org/releases) this issue was retargeted to OOo Later."
Reset to default bug assignee.