Adrian Custer wrote: > Hey all, > > I'm trying to figure out the rendering toolchain, tracking particularly > three elements: > > CRS (and projection): where these are determined, handled which > I believe I now underestand in general and will figure out > specifics later, > > Resolution (display at 96dpi versus printing at 300+ dpi) and > > Orientation(so I can pick how the map will appear on my > screen/page/powerpoint slide). > > I presume that the rendering system must be capable of handling these > things. Below, you'll find Jesse's original email outlining the > rendering steps---all my understanding to date comes from that so if my > question seems confused, I am referring to that outline. > > > 1) uDig vs. Geotools > As I understand things, uDig has a "meta" rendering system that embeds > various renderers internally. Is this meta system capable of handling > the issues above in a way that the individual renderers cannot? > Good question, uDig does define a ViewPort model that gathers together the information you describe for safe keeping. And it may make use of its own callback object into the label generation in order to handle things like rotation correctly. > 2) Handling dpi > > Does Geotools assume a screen resolution or is the rendering system > resolution independent? If the latter, where in the chain is the dpi > determined? > Interesting, I am trying to remember if the SLD specification is resolution dependent. I am not sure it is, preferring to work with things like point when it comes to font size and so on, and making use of pixels everywhere else. > As I understand Jesse's explanation, there's a decimation step that > happens once the 'styled features' have been created. This implies that > the dpi has been set by that stage. > > 3) Handling rotation > > As far as I can tell, any rotation stuff I have come across has been a > hack rather than a robust part of the renderering system. That is, we > can't rotate the output while still having the text labels appear > horizontal. Is that correct? Has anyone thought seriously about this > issue? > Interesting, no I had not thought about the issue. We just put together the following picture of SLD rendering for our own project, I have not gone through the details of how labels are "floated" to the surface of the image yet ... my impression is a strategy object should be passed in, and that as labels are rendered they should be stored for collision detection and so on once all are available. I recall David Blasby working with ways to specify a priority on labels (so city names would not be bumped off the map by street names).
In any case the idea is that the strategy (or callback) object would render things the right way up even in the face of rotation of the data underneath. It would work with screen coordinates and so on ... Cheers, sorry I did not pay attention to the specifics for you. Jody > thanks, > adrian > > P.S. Sorry to pester the list incessantly but I do hope to figure out > enough of what is going on so I can create docs to help a whole cadre of > programmers take the library and run with it. > ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Geotools-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-devel
