Lazmapviewer: overlaying a semi-transparent area

[alpine]

Is there any chance of an example which shows the code-driven creation of a layer containing one of those shaded triangles from some lat/long points, and another with a track of one or two segments again from lat/long points.

Sure. Just need some time for that, probably in late afternoon...

[MarkMLl]

At your own pace, I've got plenty else to do: initialisation files, backend database, radio reliability...

MarkMLl

[alpine]

OK, I've modified the project from the reply #12 to add programmatically the two areas shown.

What is changed:

• The layer with the two areas defined previously into the form was marked invisible
• On FormCreate one of two procedures can be invoked: AddAreas_mvMapViewer or AddAreas_mvGpsObj
• The AddAreas_mvMapViewer procedure will create a TMapLayer with two TMapArea. It should be equivalent to what is created previously with the designer.
• The AddAreas_mvGpsObj procedure will create TGPSComboLayer with two TGPSArea. It uses the mvGpsObj unit, i.e. the "original stuff" which wasn't previously meant for the designer manipulation.   

In fact, the TMapXXX classes are (more or less) designer-oriented wrappers for classes in mvGpsObj unit.

Analogically, if you want to create tracks instead of areas, you must substitute:

in AddAreas_mvMapViewer:

• TMapArea with TMapTrack (and use Layer.Tracks.Add instead of Layer.Areas.Add)
• TMapAreaPoint with TMapTrackPoint

in AddAreas_mvGpsObj:

• TGPSArea with TGPSTrack
• TGPSPoint is used in both, no need to be substituted

Hope that helps.
 

[lar]

Not sure if this would help, but several weeks ago I posted a component in topic "LazMapViewer v.0.2.7" that serves as an interface to LazMapViewer. It retrieves a street map image into a bitmap on which a user can then do their own custom drawing (like layers in a GIS) without needing to add the windowed TMapView control to their project. #Alpine provided some help in getting it to work.

The component has only two functions, one to set a map provider and another to return a map image centered at a given lon,lat, at a given zoom level, placed in a bitmap of specified width and height. Unlike LazMapViewer, the component user would be responsible for implementing their own zooming and panning operations. I needed this type of interface since my use case involved drawing thousands of line segments and circles representing a city's water and sewer lines over the street map.

[MarkMLl]

OK, I've modified the project from the reply #12 to add programmatically the two areas shown.

Thanks (and noting also Iar's comment), I'm on it and will report back.

MarkMLl

[MarkMLl]

OK, I think I see better what's going on now and hopefully this will be a good foundation for when I'm displaying live tracks.

I've extended it to display both areas and tracks but do have a slight problem in that I appear to only be able to display one or the other- even if I add a second layer.

I need to work on some RF-related stuff now, since there are various kinds of traffic which only show up at weekends. However I'm tacking in an obviously-incomplete code fragment (normally invoked in the context of form creation) below in case anybody can see my glaring mistake :-)

Code: Pascal  [Select][+][-]

1.   procedure initMapView;
2.  
3.   var
4.     scratchLayer: TMapLayer;
5.  
6.  
7.     procedure addArea(const area: TRegionDegs; colour: TColor; opacity: single);
8.  
9.     var
10.       scratchArea: TMapArea;
11.       i: integer;
12.  
13.     begin
14.  
15.       (* Add an areas object to the layer which will act as a container for     *)
16.       (* coloured static blocks, returning a reference which may be used        *)
17.       (* locally.                                                               *)
18.  
19.       scratchArea := scratchLayer.Areas.Add as TMapArea;
20.  
21.       (* Using that reference which is retained in-scope, set up drawing style  *)
22.       (* and add features.                                                      *)
23.  
24.       scratchArea.LineColor := clNone;
25.       scratchArea.FillColor := colour;
26.       scratchArea.Opacity := opacity;
27.       for i := 0 to High(area) do
28.         with scratchArea.Points.Add as TMapAreaPoint do begin
29.           Latitude := area[i].Lat;
30.           Longitude := area[i].Lon
31.         end
32.     end { addArea } ;
33.  
34.  
35.     procedure addAreas(const areas: TRegionsDegs; colour: TColor; opacity: single);
36.  
37.     var
38.       i: integer;
39.  
40.     begin
41.       for i := 0 to High(areas) do
42.         addArea(areas[i], colour, opacity)
43.     end { addAreas } ;
44.  
45.  
46.     procedure addTrack(const pLine: TPolylineDegs; colour: TColor; opacity: single);
47.  
48.     var
49.       scratchTrack: TMapTrack;
50.       i: integer;
51.  
52.     begin
53.  
54.       (* Add a tracks object to the layer which will act as a container for     *)
55.       (* coloured static polylines, returning a reference which may be used     *)
56.       (* locally.                                                               *)
57.  
58.       scratchTrack := scratchLayer.Tracks.Add as TMapTrack;
59.  
60.       (* Using that reference which is retained in-scope, set up drawing style  *)
61.       (* and add features.                                                      *)
62.  
63.       scratchTrack.LineWidth := 2;
64.       scratchTrack.LineColor := colour;
65.       scratchTrack.ConnectWidth := scratchTrack.LineWidth;
66.       scratchTrack.ConnectColor := scratchTrack.LineColor;
67.       scratchTrack.Opacity := opacity;
68.       for i := 0 to High(pLine) do
69.         with scratchTrack.Points.Add as TMapTrackPoint do begin
70.           Latitude := pLine[i].Lat;
71.           Longitude := pLine[i].Lon
72.         end
73.     end { addTrack } ;
74.  
75.  
76.     procedure addTracks(const pLines: TPolylinesDegs; colour: TColor; opacity: single);
77.  
78.     var
79.       i: integer;
80.  
81.     begin
82.       for i := 0 to High(pLines) do
83.         addTrack(pLines[i], colour, opacity)
84.     end { addTracks } ;
85.  
86.  
87.   begin
88.  
89.   (* Add a layer object to the MapView which will act as a container for areas  *)
90.   (* and tracks, returning a reference which may be used locally.               *)
91.  
92.     scratchLayer := MapView1.Layers.Add as TMapLayer;
93.  
94.   (* Using that reference which is retained in-scope, add coloured static areas *)
95.   (* to represent properties or villages which should not be overflown at low-  *)
96.   (* levels, and an "in-circuit" area within which aircraft should exercise     *)
97.   (* caution.                                                                   *)
98.  
99.     addAreas(Avoids, clRed, 1/6);
100.     addArea(InCircuit, clBlue, 1/16);
101.  
102. //    scratchLayer := MapView1.Layers.Add as TMapLayer;    DOESN'T HELP
103.  
104.   (* Again using the retained reference, add the circuit and the runway         *)
105.   (* alignment.                                                                 *)
106.  
107.     addTrack(Circuit, clGreen, 1/4);
108.     addTrack(RunwayDegs, clBlack, 1/4)
109.   end { initMapView } ;
110.  

In a day or so's time I'll write a test program with a mapview with "avoid" areas and a circuit diagram, trying to move all map centering etc. into the runtime. It obviously won't have any data-collection facilities etc., but I think it would be a useful demo and focus for discussion.

MarkMLl

[alpine]

However I'm tacking in an obviously-incomplete code fragment (normally invoked in the context of form creation) below in case anybody can see my glaring mistake :-)

Assuming:

Code: Pascal  [Select][+][-]

1. type
2.   TRegionDegs = array of TRealPoint;
3.   TRegionsDegs = array of TRegionDegs;
4.   TPolylineDegs = TRegionDegs; //array of TRealPoint;
5.   TPolylinesDegs = TRegionsDegs; //array of TRegionDegs;
6.  

Your procedure works perfectly well for me.

For what mistake you're talking about?

[MarkMLl]

Problem at present is that I can see areas, or tracks, but not both.

Leave it with me to distill everything into a simpler program... likely Monday unless it rains first.

MarkMLl

[alpine]

Problem at present is that I can see areas, or tracks, but not both.

Leave it with me to distill everything into a simpler program... likely Monday unless it rains first.

MarkMLl

You should have described the error earlier

Code: Pascal  [Select][+][-]

1.     (* Using that reference which is retained in-scope, set up drawing style  *)
2.     (* and add features.                                                      *)
3.  
4.     scratchArea.LineColor := clNone; // change it to something different

Most probably it is my mistake. Seems that clNone affects the next drawings.

[MarkMLl]

Damn... should have spotted that one and experimented. Leave it with me, but right now I don't want to interrupt the program run.

Having the area displayed has showed up an internal geometry error with without any doubt has been responsible for various classification mistakes, giving me a good order in which to investigate and fix things :-)

MarkMLl

[MarkMLl]

I /did/ describe it earlier; second para in #20 :-)

In any event, I can confirm that if the outline is set to clBlack (which in practice is barely visible hence "not unattractive" ** ) the tracks display as well.

Things aren't quite lined up yet, the kink in the approach is intentional so that pilots respect the privacy of one of the local magnates :-)

MarkMLl

** Roughly translated: "look pretty good" :-)

[alpine]

I /did/ describe it earlier; second para in #20 :-)

Yes, you did. I don't know what to say, maybe it's that we're having such freaking hot weather here that it's slowly melting my brain.

In any event, I can confirm that if the outline is set to clBlack (which in practice is barely visible hence "not unattractive" ** ) the tracks display as well.

You may try also with LineColor:=FillColor, or/and with a low opacity.

Anyway, I fixed it locally, but will commit later as there are some other glosses.

[MarkMLl]

I /did/ describe it earlier; second para in #20 :-)

Yes, you did. I don't know what to say, maybe it's that we're having such freaking hot weather here that it's slowly melting my brain.

/Hot????/ I'm in the UK, and came indoors a couple of hours ago since it was getting chilly...

You may try also with LineColor:=FillColor, or/and with a low opacity.

Anyway, I fixed it locally, but will commit later as there are some other glosses.

Yes, it appears to only be clNone which screws things... even if there is an accessible opacity for the outline having a minimal accent there is quite attractive. Please let us know if you commit changes, but I'll get onto a stripped-down demo program.

$DEITY this takes me back: GKS in the 1980s, streamed out as a CGM Metafile... I wrote some of that stuff in the DR era.

MarkMLl

[alpine]

/Hot????/ I'm in the UK, and came indoors a couple of hours ago since it was getting chilly...

At the present moment I'd trade a beer or two at your place for any whim about LMV.

Since the r9377 I'm working on an IDE track points editor. It turns out that the IDE designer mechanics is way beyond my level of comprehension (and broadly undocumented), so everything  is a complete mess at the present. I'll put some effort to isolate it and to make the commit for that fix.

[MarkMLl]

At the present moment I'd trade a beer or two at your place for any whim about LMV.

10.6C outside. Somebody's 50th birthday party nearby... youngster :-)

Since the r9377 I'm working on an IDE track points editor. It turns out that the IDE designer mechanics is way beyond my level of comprehension (and broadly undocumented), so everything  is a complete mess at the present. I'll put some effort to isolate it and to make the commit for that fix.

IDE documentation is a problem. I have absolutely no suggestions, since the project has been running so long that even the current maintainers might no longer understand every possible facet.

Which is why I think moving all initialisation into a demo program is worthwhile.

MarkMLl