[Maposmatic-dev] [PATCH] Remove the scaling step from the rendering process

[gael . utard]

From: Gael UTARD <address@hidden>

There are 2 kinds of problems with scaling:
- the rendering has some bugs (position of arrows, text halo)
- the rendered sizes (font size, road width) do not match the ones specified
  in the stylesheet

Signed-off-by: Gael UTARD <address@hidden>
---
 ocitysmap2/__init__.py                        |   26 +++++++++++++-----------
 ocitysmap2/layoutlib/abstract_renderer.py     |    4 +-
 ocitysmap2/layoutlib/single_page_renderers.py |   15 +++++--------
 ocitysmap2/maplib/map_canvas.py               |    8 ++++--
 4 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/ocitysmap2/__init__.py b/ocitysmap2/__init__.py
index 026e67e..ca2f856 100644
--- a/ocitysmap2/__init__.py
+++ b/ocitysmap2/__init__.py
@@ -61,7 +61,7 @@ The layout name is the renderer's key name. You can get the 
list of all
 supported renderers with ocitysmap.get_all_renderers(). The output_formats is a
 list of output formats. For now, the following formats are supported:
 
-    * PNG at 300dpi
+    * PNG at 72dpi
     * PDF
     * SVG
     * SVGZ (gzipped-SVG)
@@ -193,8 +193,7 @@ class OCitySMap:
 
     DEFAULT_REQUEST_TIMEOUT_MIN = 15
 
-    DEFAULT_RESOLUTION_KM_IN_MM = 150
-    DEFAULT_RENDERING_PNG_DPI = 300
+    DEFAULT_RENDERING_PNG_DPI = 72
 
     STYLESHEET_REGISTRY = []
 
@@ -456,19 +455,13 @@ SELECT ST_AsText(ST_LongestLine(
 
             # Prepare the generic renderer
             renderer_cls = renderers.get_renderer_class_by_name(renderer_name)
-            renderer = renderer_cls(config, tmpdir, street_index)
-
-            # Update the street_index to reflect the grid's actual position
-            if renderer.grid and street_index:
-                street_index.apply_grid(renderer.grid)
-                street_index.group_identical_grid_locations()
 
             # Perform the actual rendering to the Cairo devices
             for output_format in output_formats:
                 output_filename = '%s.%s' % (file_prefix, output_format)
                 try:
-                    self._render_one(renderer, output_format, output_filename,
-                                     osm_date)
+                    self._render_one(config, tmpdir, renderer_cls, 
street_index,
+                                     output_format, output_filename, osm_date)
                 except IndexDoesNotFitError:
                     LOG.exception("The actual font metrics probably don't "
                                   "match those pre-computed by the renderer's"
@@ -480,7 +473,9 @@ SELECT ST_AsText(ST_LongestLine(
         finally:
             self._cleanup_tempdir(tmpdir)
 
-    def _render_one(self, renderer, output_format, output_filename, osm_date):
+    def _render_one(self, config, tmpdir, renderer_cls, street_index,
+                    output_format, output_filename, osm_date):
+
         LOG.info('Rendering to %s format...' % output_format.upper())
 
         factory = None
@@ -525,6 +520,13 @@ SELECT ST_AsText(ST_LongestLine(
             raise ValueError, \
                 'Unsupported output format: %s!' % output_format.upper()
 
+        renderer = renderer_cls(config, tmpdir, dpi, street_index)
+
+        # Update the street_index to reflect the grid's actual position
+        if renderer.grid and street_index:
+            street_index.apply_grid(renderer.grid)
+            street_index.group_identical_grid_locations()
+
         surface = factory(renderer.paper_width_pt, renderer.paper_height_pt)
         renderer.render(surface, dpi, osm_date)
 
diff --git a/ocitysmap2/layoutlib/abstract_renderer.py 
b/ocitysmap2/layoutlib/abstract_renderer.py
index 17f23b0..f2bc858 100644
--- a/ocitysmap2/layoutlib/abstract_renderer.py
+++ b/ocitysmap2/layoutlib/abstract_renderer.py
@@ -212,7 +212,7 @@ class Renderer:
 
         ctx.restore()
 
-    def _create_map_canvas(self, graphical_ratio,
+    def _create_map_canvas(self, width, height, dpi,
                            draw_contour_shade = True):
         """
         Create a new MapCanvas object.
@@ -228,7 +228,7 @@ class Renderer:
         # Prepare the map canvas
         canvas = MapCanvas(self.rc.stylesheet,
                            self.rc.bounding_box,
-                           graphical_ratio)
+                           width, height, dpi)
 
         if draw_contour_shade:
             # Area to keep visible
diff --git a/ocitysmap2/layoutlib/single_page_renderers.py 
b/ocitysmap2/layoutlib/single_page_renderers.py
index 5ae2f9a..0fec650 100644
--- a/ocitysmap2/layoutlib/single_page_renderers.py
+++ b/ocitysmap2/layoutlib/single_page_renderers.py
@@ -55,7 +55,7 @@ class SinglePageRenderer(Renderer):
 
     MAX_INDEX_OCCUPATION_RATIO = 1/3.
 
-    def __init__(self, rc, tmpdir,
+    def __init__(self, rc, tmpdir, dpi,
                  street_index = None, index_position = 'side'):
         """
         Create the renderer.
@@ -130,8 +130,9 @@ class SinglePageRenderer(Renderer):
 
         # Prepare the map
         self._map_canvas = self._create_map_canvas(
-            float(self._map_coords[2]) / # W
-            float(self._map_coords[3]) ) # H
+            float(self._map_coords[2]),  # W
+            float(self._map_coords[3]),  # H
+            dpi )
 
         # Prepare the grid
         self.grid = self._create_grid(self._map_canvas)
@@ -376,10 +377,6 @@ class SinglePageRenderer(Renderer):
         # Draw the rescaled Map
         ctx.save()
         rendered_map = self._map_canvas.get_rendered_map()
-        ctx.scale(map_coords_dots[2]
-                    / rendered_map.width,
-                  map_coords_dots[3]
-                    / rendered_map.height)
         mapnik.render(rendered_map, ctx)
         ctx.restore()
 
@@ -491,7 +488,7 @@ class SinglePageRendererNoIndex(SinglePageRenderer):
     name = 'plain'
     description = 'Full-page layout without index.'
 
-    def __init__(self, rc, tmpdir, street_index):
+    def __init__(self, rc, tmpdir, dpi, street_index):
         """
         Create the renderer.
 
@@ -500,7 +497,7 @@ class SinglePageRendererNoIndex(SinglePageRenderer):
            tmpdir (os.path): Path to a temp dir that can hold temp files.
            street_index (StreetIndex): None or the street index object.
         """
-        SinglePageRenderer.__init__(self, rc, tmpdir, None, None)
+        SinglePageRenderer.__init__(self, rc, tmpdir, dpi, None, None)
 
 
     @staticmethod
diff --git a/ocitysmap2/maplib/map_canvas.py b/ocitysmap2/maplib/map_canvas.py
index 392a1c3..3ba0cd9 100644
--- a/ocitysmap2/maplib/map_canvas.py
+++ b/ocitysmap2/maplib/map_canvas.py
@@ -30,6 +30,7 @@ except ImportError:
 import os
 
 from ocitysmap2 import coords
+from layoutlib.commons import convert_pt_to_dots
 import shapes
 
 l = logging.getLogger('ocitysmap')
@@ -46,7 +47,7 @@ class MapCanvas:
     their respective alpha levels.
     """
 
-    def __init__(self, stylesheet, bounding_box, graphical_ratio):
+    def __init__(self, stylesheet, bounding_box, _width, _height, dpi):
         """Initialize the map canvas for rendering.
 
         Args:
@@ -62,6 +63,7 @@ class MapCanvas:
         # is adjusted (extended) to fill the destination zone. See
         # _fix_bbox_ratio for more details on how this is done.
         orig_envelope = self._project_envelope(bounding_box)
+        graphical_ratio = _width / _height
 
         off_x, off_y, width, height = self._fix_bbox_ratio(
                 orig_envelope.minx, orig_envelope.miny,
@@ -71,8 +73,8 @@ class MapCanvas:
         envelope = mapnik.Box2d(off_x, off_y, off_x+width, off_y+height)
 
         self._geo_bbox = self._inverse_envelope(envelope)
-        g_height, g_width = self._geo_bbox.get_pixel_size_for_zoom_factor(
-                stylesheet.zoom_level)
+        g_width  = int(convert_pt_to_dots(_width, dpi))
+        g_height = int(convert_pt_to_dots(_height, dpi))
 
         l.debug('Corrected bounding box from %s to %s, ratio: %.2f.' %
                 (bounding_box, self._geo_bbox, graphical_ratio))
-- 
1.7.5.4