Imgkap - kap File Converter Tool

[Rasbats]

Attempting to make a KAP to overlay soundings from survey_pi onto other raster charts.

PNG and TIF images with a transparent background can be made but the KAP chart produced by IMGKAP and also MAPC2MAPC renders these images with a white background, obscuring the background chart.

The only way found to display the soundings as an overlay so far is to make a KMZ which includes the transparent image file and then open this file with Google Earth. Using GE2KAP I can make a KAP which shows the soundings superimposed on an OpenCPN chart (Make land transparent).

Does the KAP standard allow a transparent background?

Mike

[seandepagnier]

kap doesn't support transparency, but we could make an extension for opencpn to do it.

[seandepagnier]

Also,

We should invent a new format for imagery charts. This format should probably use jpeg or possibly jpeg2000 compression. This will reduce the file size to 15% of a kap file without any loss in quality. We would then implement an extension to support transparency. I don't think we care about partial transparency, so a bitmap or possibly specifying a transparent color would do.

opencpn should treat this type of chart differently using a different color in the chart bar than typical raster charts, and be able to overlay it on top of raster charts as well as allowing blending to turn on and off the transparent area.

Finally, this chart format should support multiple images of the same area at different dates to reveal the area at different times to show different tide states as well as different sea states. These times should be referenced to what the tide was at that time and what the swell conditions were at that time.

[Rasbats]

One of my options is to use the OpenCPN plugin GE2KAP, which can make a chart from a section of OpenCPN. With the survey_pi plugin enabled the soundings are displayed. We get a screen shot with the soundings rendered. Example attached.

The first item on the wish list is for an OpenCPN overlay format with a transparent background.

The images for display on OpenCPN need to be very portable. I have not been able to make a JPG from QGis with a transparent background. GeoTiffs are large but do retain the transparent background. Could these be accommodated?

A lot of soundings have gone into OpenSeaMap and they are also looking at means of display. The TeamSurv raw/processed data seems closed to contributors once it has been uploaded.

Mike

[autumnbreeze27]

Originally Posted by boat_alexandra

Also,

We should invent a new format for imagery charts. This format should probably use jpeg or possibly jpeg2000 compression. This will reduce the file size to 15% of a kap file without any loss in quality. We would then implement an extension to support transparency. I don't think we care about partial transparency, so a bitmap or possibly specifying a transparent color would do.

Jpeg doesn't support transparency, PNG might be a better choice.

[Rasbats]

Thanks. A georeferenced PNG with a transparent background made from QGis is about the same size as the JPG from the same source.

Mike

[HappySeagull]

Here's an idea from another developer..."OSMAND"


here, it is applying "GeorgiaStraits-North.sqlitedb" as an overlay on an OpenStreetMap. note the little blue slider that controls transparency.
Making these "sqlitedbs" is a bit of work !
opining,
.... I find transparent map overlays are not really useful - neither is plain, combined they are a blur. But in this road-driver application, it is a way to see and switch-to charts- not as good imo, as Opencpn for the purpose.

[bcn]

Questions and issues coming to my mind:

A chartlet with some transparent areas will show what "below"?

Do we need chart layers?

Or is this chartlet something like an user created object? --> Draw-plugin...
What do we see then on the canvas? Thinking about an underlying Vector chart.

How does this work with quilting? Raster and Vector mixed...
Do the chartlet(s) quilt?

Hubert

Btw.: creating a chartlet with imgkap starting from a png with alpha channel gave us Black for the transparent areas

[HappySeagull]

for me, it'd seem the simplest way to do what rasbats has shown is to use icons ala the opencpn/s57 data folder and "call them up" with a gpx/xml...? something that might be included in the draw plugin....?

[bcn]

Happy...

a soundings/sounding path or depth line object (nested). Yes.

And think about exporting this. Or people who want a chartlet for a second, different system.

Boat_alexandra/Sean is proposing a more challenging scenario though.

But I'm with you that the draw-PI can be the home for the first solution.

Hubert

[Rasbats]

Happy .....

My screenshot was the product of my fork of survey_pi, generated from an sqlite database.

GitHub not yet updated.

I will take a closer look at O-Draw.

Mike

[rgleason]

There is a lot going on here, so bear with my 2 cents, keeping in mind I have not used imgkap much if at all. I think the idea Sean threw out is trying to provide a tool for many uses, one of them being a good way for OpenCPN to provide "layers" of various types of "user" information in an comprehensible and easily managed way.

Types of Information (not comprehensive)
-Google satellite pics (GeoKap)
-Weather overlays (weatherfax_pi)
-Satellite weather photos
-Navtex
-Draw_pi objects
- Survey data - (sorry Mike, almost forgot that)
-Climatology data
-Grib? (maybe not)etc.

with the possibly of having capabilities such as these
* location (coordinates) included in the file format
* transparency & controls (maybe on off, maybe an adustment bar)
* saved views - remember which layers were on in a given view.
* order of rendering of layers, select which one last, remembering that.
what else?

Can a Georeferenced PNG be considered a layer? Can it be the tool needed?

Maybe baby steps are needed, but BCN has asked this question in a different way earlier, thinking about all the different types of data and uses and how it impacts O. It certainly does not hurt to think/discuss this carefully, so there is a reasonable plan for development with less backing up and undoing things. Perhaps even with some shared tools that can be used by several plugins, which will leverage capabilities (think of watchdog and ocpn_draw_pi developments using guid)

[rgleason]

It is very likely I don't understand all the issues, but

Tide data is another type, that is really vectors over time, just like grib.

Also another capability is play controls over time, like the grib_pi

[leamas]

[many years pass...]

...and the idea to make imgkap part of linux distros pops up. Is is basically no problem besides the license legal issue.

As I understand it, the author intends to make this software freely available. However, the phrasing in the code is not clear enough to survive the reviews performed in linux distros.

So, could you please clarify under what conditions the software could be used? In the end you are the author and copyright holder so it's up to you. That said, I can see some alternatives:

• You could make a new release of the source code where you state that this software is in public domain.
• Or, you could add text to the source code under what license (e. g., GPL version 3) user could use the code.
• Or, simplest, if you just replied here that imgkap is in public domain it is sufficient for packagers.

So, ping, are you still here MdJ?

[nohal]

Originally Posted by leamas

[many years pass...]

...and the idea to make imgkap part of linux distros pops up. Is is basically no problem besides the license legal issue.

As I understand it, the author intends to make this software freely available. However, the phrasing in the code is not clear enough to survive the reviews performed in linux distros.

So, could you please clarify under what conditions the software could be used? In the end you are the author and copyright holder so it's up to you. That said, I can see some alternatives:

• You could make a new release of the source code where you state that this software is in public domain.
• Or, you could add text to the source code under what license (e. g., GPL version 3) user could use the code.
• Or, simplest, if you just replied here that imgkap is in public domain it is sufficient for packagers.

So, ping, are you still here MdJ?

Given the only more or less maintained version of this code in the last years is https://github.com/nohal/imgkap I'm a little afraid not.

Pavel