[Openev-discuss] linear_zoom problem (?)

[s d. <syl...@ya...>]

Hi,

I'm investigating why openev doesn't display
OGR/S57 like other viewer (7C & dkartlook).

Here what I found:

1- replace code in gvviewarea.c:2096:

gv_view_area_fit_extents()  
  ...
  zoomx = view->state.shape_x / width;
  zoomy = view->state.shape_y / ABS(height);
  
  // ADDED
  zoomx = zoomx * cos(lly);

  // COMMENTED
  //view->state.linear_zoom = MIN(zoomx, zoomy);

  // ADDED
  view->state.linear_zoom_x = zoomx;
  view->state.linear_zoom_y = zoomy;


2- change struct _GvViewAreaState in gviewarea.h

from:
  gvfloat linear_zoom;     /* xy plane zoom */

to

  gvfloat linear_zoom_x;   /* xy plane zoom */
  gvfloat linear_zoom_y;   /* xy plane zoom */


3- adpate code where the compiler choke :)


After that S57 is displayed somewhat better.

So I'm woundering if there is a reason for
having "round" pixel (ie the zoom is the same
in X and Y) for GIS purpose!

S57 is in Mercator to preserve angle so pixel
can only be "round" at the equator. 

Or maybe I'm missing a step somewhere (PROJ!).


Thanks,

Sylvain.



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