[GRASS-dev] Re: [GRASS GIS] #72: PNG driver: boundary rendering is off by one pixel

[GRASS GIS]

#72: PNG driver: boundary rendering is off by one pixel
--------------------------+-------------------------------------------------
  Reporter:  hamish       |       Owner:  grass-dev at lists.osgeo.org    
      Type:  defect       |      Status:  new                          
  Priority:  blocker      |   Milestone:  6.4.0                        
 Component:  default      |     Version:  svn-develbranch6             
Resolution:               |    Keywords:  d.vect, rendering, PNG_DRIVER
  Platform:  Unspecified  |         Cpu:  Unspecified                  
--------------------------+-------------------------------------------------
Comment (by hamish):

 Replying to [comment:13 glynn]:
 > If you want quality, I would expect both the cairo and PS drivers
 > to produce better results overall than either PNG or XDRIVER.

 both are less WYSIWYG. Cairo thickens and antialiases lines, and PS driver
 in 6.4 is limited by 6.4, and needs to be passed through pstoimg or
 ghostscript to get the web/presentation image which has its own
 rasterization quirks.

 > You might also run into problems with the distinction between
 > polylines and multiple line segments (caps versus joins) being
 > visible.

 unrelated, but ps.map's region box command has that problem,
 obvious once you set the width a bit wider.



 I ran some 'd.vect rend=' tests with the latest 6.4svn (w/ Polygon.c
 commit). screenshots & scripts here:
  http://bambi/hamish/grass/bugs/d.vect/dec2008/

 {{{
 results for render mode trials 5 Dec 2008

 coastline
 =========

 6.3.0
 -----
 xdriver:   R, C perfect; G near perfect; D, L off (x+y)
 pngdriver: R, C off (x); G perfect; D off (y); L off(x+y)


 6.4.svn 20081205 (with Polygon.c patch)
 -------
 xdriver:   R, C, G perfect; D, L off (x+y)
 pngdriver: R, C off (x); G perfect; D, L off (x)
 gis.m: off (x)

 inter-version
 -------------
 xdriver-   results mostly unchanged (fixed 1 pixel in G)
 pngdriver- D,L slightly improved



 boxes
 =====
 6.4svn xdriver: D, L off (x+y)
 6.4svn png driver: all look good.
 6.4svn gis.m: looks good
 }}}


 Hamish

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/72#comment:14>
GRASS GIS <http://grass.osgeo.org>