KML Overlay Plugin

[phiggins]

Hi Tore,

When you say you displayed the kmz file, did you display it using the plugin or GE? The plugin allows you to overlay KML data on opencpn including kmz files with JPGs. The new version of GE2KAP can now create a KMZ file of an area of GE instead of a chart. The JPG is included in the the KMZ file and shows the GE area. If you opened the KMZ file with GE it would just overla the same picture onto GE.

I sent the new version to a couple of other users and so far good feedback. I'll send you a copy but you'll have to get the plugin working to see how it works.

[phiggins]

It would be nice if this plugin included a slider to adjust the transparency of the overlay.

[LeaseOnLife]

Originally Posted by phiggins

It would be nice if this plugin included a slider to adjust the transparency of the overlay.

[SethDart]

Originally Posted by phiggins

It would be nice if this plugin included a slider to adjust the transparency of the overlay.

Well, I already replied to this request but maybe only privately. Here's a summary:

KML/KMZ is a container and, as such, can contain multiple objects (point, line, polygon, ground overlay, screen overlay, etc.)
Every object can have colour and transparency set, each being possibly different.

So (to me) the problem is how a user interface can provide this feature (altering transparency) to the user?

Right now, only the container (KML/KMZ) is listed in the list box. If you change transparency, how would it alter each object's settings?

Here's an example:
Say I've one KML/KMZ file with 2 objects (lines, polygons or ground overlay, no matter)
Object #1 has 20% transparency
Object #2 has 60% transparency
When I move the transparency slider to 50%, what should I get?
- option 1: 50% of 20% for object #1 (that makes 10%) and 50% of 60% for object #2 (30%)
- option 2: 50% for each object (whatever the initial value was)
- option 3: some math that would keep ratio (20% vs 60%) between objects but allowing 0-100% span.

As you can see in this example, this is not an easy task. With option 1, original transparency would be the maximum allowed, you can only decrease it (there might be just another option being original% + slider position%). With option 2, you lose original transparency and cannot get it back without resetting your original data. option 3 might be a good compromise but you may not be able to get object #1 transparency to 100% (because of the ratio with object #2)

The other solution would be to show each and every object in the list box and be able to change transparency selectively... Well, that's a Pandora box: then some would want to change colour, then show/hide objects, then maybe move them.

The purpose of this plugin was to display a KML/KMZ file and I really don't know if I want to open that Pandora box ;-)

I'll be off sailing for the next 10 days, I'll try to take some time to make some of the requested changes to this plugin.

Comments welcome :-D

Regards,
Jean-Eudes

[bcn]

Originally Posted by SethDart

Here's an example:
Say I've one KML/KMZ file with 2 objects (lines, polygons or ground overlay, no matter)
Object #1 has 20% transparency
Object #2 has 60% transparency
When I move the transparency slider to 50%, what should I get?
- option 1: 50% of 20% for object #1 (that makes 10%) and 50% of 60% for object #2 (30%)
- option 2: 50% for each object (whatever the initial value was)
- option 3: some math that would keep ratio (20% vs 60%) between objects but allowing 0-100% span.

....

Comments welcome :-D

Regards,
Jean-Eudes

Jean-Eudes,

you might have a look at Inkscape, how they handle this:

- Apply transparency to an object
- Select a second one and group those two
- Apply transparency to the grouped object

It looks like option3 and is probably the expected behavior from a user's point of view.
That's like flattening all the objects into one layer and applying transparency to that one.

Hubert

[phiggins]

I have decided due to this revelation to make the the kmz overlays created by GE2KAP completely opaque and if you overlay a chart to let you adjust the transparency of the overlay in GE2KAP. Attached is an example of what this would look like for a harbor Santos Harbor in Brazil lat:023 58.5774 S lon: 046 23.5575 W.

[phiggins]

SethDart,

Just a guess but isn't it likely that most of the time the opacity of all the objects in the KMZ container will have a value of 100%?

Could the logic be:

If all the objects have the same opacity, show a slider that allows you to adjust all of them by the same amount. if they are not the same, don't show a slider.

[SethDart]

Originally Posted by phiggins

Just a guess but isn't it likely that most of the time the opacity of all the objects in the KMZ container will have a value of 100%?

That may be the case for GroundOverlay but remember KML can contain others objects. For example, I can display a zone with red colour with a polygon, using 60% transparency for fill colour (border colour is set separately) so I can see the chart below. That could be used for dangerous zone, or maybe to display delimited regatta zone (as done in America's Cup World Series views). I'm sure there's a lot of use for this. That could be used for NtoM: no transparency to hide some nav objects on the chart, some transparency to add text or drawings above chart.

Originally Posted by phiggins

Could the logic be:

If all the objects have the same opacity, show a slider that allows you to adjust all of them by the same amount. if they are not the same, don't show a slider.

I can do that, but I would rather disable the slider instead of hiding it. And, as border colour (thus transparency) is separate from fill colour, it'll be disabled for most objects, creating a bad user experience, IMHO. With the example of polygons, if you don't want borders, you set it to whatever colour and transparency to 100%, same for fill (if you only want border) so transparency is different and the slider will be disabled. Here comes the Pandora box. Transparency is not a single setting, unfortunately.

I'll try to come with a solution while sailing in the next 10 days.

Thanks for your comments.

Regards,
Jean-Eudes

[bcn]

Originally Posted by SethDart

I'll try to come with a solution while sailing in the next 10 days.

Thanks for your comments.

Regards,
Jean-Eudes

So have fun and fair winds!

Here a bit more literature from SVG:
Clipping, Masking and Compositing

Hubert

[Mike_S]

First post, and new to the open source community, so bear with me. I have OpenCPN 2.5.0 installed successfully, on Windows 7 64 bit. I've created a KML file using ArcGIS software, and found this plug-in. However, can't get it to work? I've downloaded what I think is the most recent dlls, installed as shown below:

C:\Program Files (x86)\OpenCPN\libexpat.dll
C:\Program Files (x86)\OpenCPN\plugins\kmloverlay_pi.dll

Does this plug-in only work on a newer beta version which the user has to compile, or with the standard download of OpenCPN?

Being someone who works with GIS/mapping software, I see the use of having this KML overlay being powerful for me.

Thanks for any help.

Mike

[nohal]

Mike...
Yes, this plugin needs the latest additions to the API. You don't have to compile the beta code, Windows installer downloads for the latest development version are available just below the stable version on Download OpenCPN | Official OpenCPN Homepage. We are currently finalizing the next stable release, so the latest beta is 99.9% percent of what OpenCPN 3.0 will be in the next days - I would say safe to use, actually better than what 2.5.0 is.

Pavel

[sinbad7]

Mike..

Have you tried either GE2KAP or C2GPXKML?
Do a Google on GE2KAP and you will find the download site.

Tore

[Mike_S]

Thanks Pavel, that did it. Tore - no, haven't checked them out yet. I grabbed GE2KAP and tried, the rexx ?? interpreter gave me an error on the install, but I'll play around with it, looks interesting.

[phiggins]

Just to let you know that I have not yet uploaded to my website the GE2KAP version that creates KMZ files that can be used on this KML overlay plugin.

If you want to try the version of GE2KAP that does this drop me an email and I'll send it to you: phiggins()gmn-usa.com (replace the () with a @)

[boraxtr]

I installed OpenCPN 2.6.1729,

- then libexpat .dll + zlib1.dll into the root (C:\Program Files\OpenCPN) and
- kmloverlay_pi.dll into the plugin folder (C:\Program Files\OpenCPN\plugins)

I see nothing at the menu bar when I run OCPN.