Hi all,

I got some strange images when loaded tif files using the DotSpatial release 0.11.9.6 Oct 7 2011, Beta.

It seems that it read 3 band image as 256 colors.

Please see the images:
http://imageshack.us/photo/my-images/26/fig1e.png/ >> a mid size tif image loaded in DemoMap and ArcGIS
http://imageshack.us/photo/my-images/855/fig2.png/ >> a big size tif image loaded in DemoMap and ArcGIS
http://imageshack.us/photo/my-images/441/fig3.png/ >> small size jpg image load error in DemoMap and loaded in ArcGIS

Does anyone are facing the same thing?

In DemoMap you are looking at only one band, which has been displayed with high values with a yellow color and low values as green. We'll need to add a feature so that you can view all three (R,G,B) bands as a composite image.

You should be all set in the latest version of DotSpatial. Be sure that you don't include the Gdal extension as it will provide different behavior.

Feel free to let us know your results!

Great!!! I will test it!!!

Thanks!

Hi mudnug,
I make the test, and it will works. Thank you very much.

Then if I would like to use in my project the GDAL Extension, I will see my geotiff file only in one band. Is it right?

Thank you again,

a

Presently, that is the behavior in the GDAL Extension.

Hi mudnug,
thank you, you are always very kind.

Then if I have a RGB geotiff aerial photo, and I load it using gdal extension I will see it always as 8 bit image. Is there some way to compose the three band inside DotSpatial starting from GDAL geotiff loading?

Best regards,

a

The GDAL Extension needs some work and I've been looking at setting it up for reading larger files, but I'm not sure about this issue. Feel free to grab the source and look at GdalImage.cs. There are some methods like

ReadArgb()

that suggest it was intended to read (display) more than one band.

Hi mudnug,
once again thank you.

I have downloaded MapWindow GIS, and I have added the same geotiff in MapWindow and in Demomap.exe; I'm using Demomap you have in DotSpatial 1.1 release with GDAL extension loaded.

As you can see here, both load properly my geotiff, and as you know Demomap load only one band and I have a 256 colors map.
The strange thing is that it seems that also MapWindow use a 256 color map, bat it uses colors much more similar to those of the originale RGB image.
Does MapWindows use GDAL extension? Is there some color method in dotspatial that I can use to adapt a 256 color map to a RGB image?

Thank you,

Andrea

DotSpatial's use of GDAL isn't up to par with MapWindow 4.x, yet. MapWindow uses GDAL, though the source is pulled into the ocx, instead of linking to it.

My guess is that MapWindow 4.x uses all three bands, where DotSpatial only uses one. The code probably needs to be modified to get the result you want.

Hi mudnug,
ok, probably I will not use GDAL extension, I'm not a great developer.

Is there a way, without GDAL extension, to map no-data value in a RGB aerial photo?

Thank you,

Andrea

Hi mudnug,
I have solved.

In my project I use gdalwarp utility, I run this command:

gdalwarp -t_srs epsg:32633 -tps -dstnodata 0 -co COMPRESS=JPEG -co JPEG_QUALITY=80 -tr 0.5 0.5 input.tif output.tif

If I load the output image using GDAL extension, DotSpatial maps no-data value. If I remove GDAL extension it does not map properly no-data value.

I have changed my command in:

gdalwarp -t_srs epsg:32633 -tps -dstalpha -co COMPRESS=DEFLATE  -tr 0.5 0.5 input.tif output.tif

Now I load my output.tif as IImageData, and no-data value is properly mapped.

Thank you very very much,

Andrea