support custom non-crs proj transforms with new proj api again

[josch]

No description provided.

[codecov]

Codecov Report

Merging #4309 (10801d4) into master (1ba1278) will decrease coverage by 0.03%.
The diff coverage is 55.40%.

@@            Coverage Diff             @@
##           master    #4309      +/-   ##
==========================================
- Coverage   75.04%   75.00%   -0.04%     
==========================================
  Files         511      511              
  Lines       36546    36610      +64     
==========================================
+ Hits        27425    27461      +36     
- Misses       9121     9149      +28     

Impacted Files	Coverage Δ
src/proj_transform.cpp	74.61% <55.40%> (-4.54%)	⬇️
plugins/input/sqlite/sqlite_featureset.cpp	89.06% <0.00%> (-1.57%)	⬇️
src/text/itemizer.cpp	87.61% <0.00%> (-0.96%)	⬇️
src/png_reader.cpp	83.67% <0.00%> (+0.68%)	⬆️
src/svg/output/process_symbolizers.cpp	100.00% <0.00%> (+2.50%)	⬆️

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[josch]

I marked this pull request as "Draft" for two reasons:

1. unit tests are missing (and the decrease in coverage) -- please advice where you think I should put a good test for this alternative code path
2. my tracks are not yet rendered correctly -- more on that now

So the basic I idea of this pull request to allow non-crs transforms already works well. Here is a rendering of the polygons for a tinshift transform:

And here is a mapnik rendering with the map warped accordingly:

The problem is, the gpx track doesn't get warped as well but isn't showing up at all. I'm using the python mapnik bindings with the commits from the proj6 branch and am running it like this:

    tinshift = mapnik.Projection("+proj=pipeline +step +proj=webmerc +step +proj=tinshift +file=/tmp/tinshift.json")
    m = mapnik.Map(600, int(600*height/width))
    mapnik.load_map_from_string(m, open("mapnik.xml").read(), False, "/usr/share/openstreetmap-carto-common")
    gpxstyle = mapnik.Style()
    gpxrule = mapnik.Rule()
    gpxsym = mapnik.LineSymbolizer()
    gpxsym.stroke = mapnik.Color('blue')
    gpxsym.stroke_width = 5
    gpxsym.stroke_opacity = 0.5
    gpxrule.symbols.append(gpxsym)
    gpxstyle.rules.append(gpxrule)
    m.append_style('GPXStyle', gpxstyle)
    gpxlayer = mapnik.Layer('GPXLayer')
    gpxlayer.datasource = mapnik.Ogr(file = sys.argv[1], layer = 'tracks')
    gpxlayer.styles.append('GPXStyle')
    m.layers.append(gpxlayer)
    m.aspect_fix_mode = mapnik.aspect_fix_mode.GROW_BBOX
    m.zoom_to_box(mapnik.Box2d(mapnik.Coord(0, 0), mapnik.Coord(width, height)))
    m.srs = tinshift.params()
    surface = cairo.SVGSurface("out.svg", 600, int(600*height/width))
    mapnik.render(m, surface)
    surface.finish()

The same code renders the track just fine if I replace my +proj=pipeline with webmerc (see my tinshift debug rendering above -- the track draws just fine in blue). That's why I think the culprit is the non-webmerc projection. I'm also getting the following errors on the terminal when running above code:

webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
webmerc: Invalid latitude
ERROR 1: IllegalArgumentException: Points of LinearRing do not form a closed linestring
ERROR 1: IllegalArgumentException: Points of LinearRing do not form a closed linestring

Those errors go away if I comment out the line m.layers.append(gpxlayer). That's why I think that there is something missing in the parts that are involved in rendering the tracks. Can you give me some pointers?

[mathisloge]

@josch you can better view coverage here : https://app.codecov.io/gh/mapnik/mapnik/compare/4309/diff
as the codecov reporting in github is a bit buggy..

[josch]

@josch you can better view coverage here : https://app.codecov.io/gh/mapnik/mapnik/compare/4309/diff
as the codecov reporting in github is a bit buggy..

Thanks, I think I now added a test case that correctly executes the new code path.

The only thing missing is the problem with correctly transforming my gpx layer. Any idea what could be wrong?

[mathisloge]

I can't really answer this, but maybe @artemp could.

[josch]

Hi, I wanted to send another friendly ping. Any update on this? Thanks!

[artemp]

Hi, I wanted to send another friendly ping. Any update on this? Thanks!

Hi @josch, sorry I didn't have a chance to check your PR, yet. I made a reminder for Monday. Thanks for your patience.

[artemp]

@josch - PR looks good, thanks. Could you share your GPX file and tinshift.json ?

[josch]

@josch - PR looks good, thanks. Could you share your GPX file and tinshift.json ?

Sure, here you go: mapniktinshift.zip

[artemp]

@josch I finally had a chance to test your tinshift pipeline. I can replicate this issue with the following minimal Python script:

import mapnik
tinshift = mapnik.Projection("+proj=pipeline +step +proj=webmerc +step +proj=tinshift +file=/tmp/tinshift.json")
wgs84 = mapnik.Projection("epsg:4326")
tr=mapnik.ProjTransform(wgs84, tinshift)
tr.forward(mapnik.Coord(9.974552, 49.789942))

webmerc: Invalid latitude
Coord(inf,inf)

(NOTE: I had to disable adding +type=crs !!)

diff --git a/src/proj_transform.cpp b/src/proj_transform.cpp
index fa141cf30..a54fe1a20 100644
--- a/src/proj_transform.cpp
+++ b/src/proj_transform.cpp
@@ -100,7 +100,7 @@ std::string pj_add_type_crs_if_needed(const std::string &str) {
     if ((str.rfind("proj=", 0) == 0 || str.rfind("+proj=", 0) == 0 ||
          str.rfind("+init=", 0) == 0 || str.rfind("+title=", 0) == 0) &&
         str.find("type=crs") == std::string::npos) {
-        ret += " +type=crs";
+        //ret += " +type=crs";
     }
     return ret;
 }

Without the patch above ^ I was getting invalid PROJ string error

Omitting webmerc from pipeline e.g

tinshift = mapnik.Projection("+proj=pipeline +step +proj=tinshift +file=/home/artem/projects/mapnik/bugs/4309/tinshift.json")
tr=mapnik.ProjTransform(wgs84, tinshift)
tr.forward(mapnik.Coord(9.974552, 49.789942))
Coord(6505465.205830257,286994.6673597563)

works as in it produces some output. I don't really know much about pipeline framework, perhaps you can ask proj developers if your original definition is valid? If 'yes' then something is not right on mapnik side and needs more investigations/fixes. HTH