[Gvsig_english] Code Question - raster layers

Wed Sep 16 14:06:38 CEST 2009

Hello, Aldo.

Yes, we know that the VM sometimes (I think J9 doesn't) uses a new thread when dealing with images (reading or resampling), that's why we wrote this method:

public static Image getScaled(Image img, int newwidth, int newheight);

in the ResourceReader class, but I think we forgot to use it in the draw method of the WKFRasterDriver class :-/

So I think you have these three options:

- Use the J9 version (as I said, I think J9 loads/resamples images in the main thread)
- Edit the code, use that method and compile
- Convert your JPG/PNG/GIF images to ECW with Gdal ( http://fwtools.maptools.org )

Even if you use J9 or fix the bug yourself, I recommend using ECW because the other formats are a great bother. After loading one of those images, the application becomes more unstable.

Thanks for reporting this problem.

As for the rotation, we simply ignore it. The second and third parameters of the world file (*.WLD) are not used at all, sorry. Again, with Gdal you can convert a rotated image (PNG/JPG/GIF + WLD file with non-zero values in second and third line) into a ECW file which will obviously have black triangles by the margins. In this case, you need two steps:

gdalwarp image.jpg image.tif
gdal_translate -of ecw image.tif image.ecw

Regards,

Juan Lucas Domínguez Rubio
---
Prodevelop SL, Valencia (España)
0° 22' 49.62" W, 39° 28' 25.45" N
Tlf.: 96.351.06.12 -- Fax: 96.351.09.68
http://www.prodevelop.es <http://www.prodevelop.es/> 
---

________________________________

De: gvsig_internacional-bounces at listserv.gva.es en nombre de Aldo Stracquadanio
Enviado el: mié 16/09/2009 13:00
Para: Users and Developers mailing list
Asunto: Re: [Gvsig_english] Code Question - raster layers

Hi Juan,

I know about the limitation of 400k pixels, I will send you the
exported project I'm working on as soon as I will be in my office. The
problem with resampling of the image is that a
clipping-translating-composition can't resolve the rotation part of a
generic affine transform (and I think in my image it's needed a little
rotation too).

Moreover I see that you use the getScaledInstance method to get a
scaled instance of the image and immediatly after this you check for
width. This often gives me -1 (causing an exception) because this
method (like the most of the graphics methods of CDC) can exibit an
asynchronus behavior; have you ever had such problems?

Regards,
Aldo Stracquadanio.

2009/9/15 Juan Lucas Dominguez Rubio <jldominguez at prodevelop.es>:
> Hello, Aldo.
>
> As you say, the Graphics2D class in CDC knows nothing about affine
> transforms, so you always have to provide 'final' coordinates, that is,
> screen coordinates.
>
> The Image class has a resample method and of course there are ways to clip
> an image, so all you have to do is clipping and resizing the image until you
> have the final image, and then paste it in the correct coordinates on the
> screen, that's what the WKRasterDriver does.
>
> These images (we're talking about JPG, PNG and GIF images; the ECW driver is
> totally different) are very memory-consuming and can only be loaded if the
> have less than 400,000 pixels. If we tried to open larger images, the
> virtual machine itself would be at risk.
>
> We tried to do the clipping and resampling in such a way that we never need
> to instantiate a large image, but maybe this is not always possible.
>
> Can you send us the log files under \gvSIGMobile\log\ or even the image
> itself?
>
>
> Regards,
> Juan Lucas Domínguez Rubio
> ---
> Prodevelop SL, Valencia (España)
> 0° 22' 49.62" W, 39° 28' 25.45" N
> Tlf.: 96.351.06.12 -- Fax: 96.351.09.68
> http://www.prodevelop.es <http://www.prodevelop.es/> 
> ---
>
>
>
> -----Mensaje original-----
> De: gvsig_internacional-bounces at listserv.gva.es en nombre de Aldo
> Stracquadanio
> Enviado el: mar 15/09/2009 18:32
> Para: gvsig_internacional at listserv.gva.es
> Asunto: [Gvsig_english] Code Question - raster layers
>
> Hi everybody,
>
> I'm reading the phoneME Mobile source code, but I can't understand
> something about the WKFRasterDriver: if there is no support for
> AffineTransform in CDC, how do you obtain a "shear" effect using only
> scaling-translation operations? I can't figure it out and, as well,
> the raster layer visualization is not working at all on my
> installation: in my opinion there is some problem with the asynchronus
> behaviour of the Image.getScaledInstance method since I get a "Cannot
> resample (down)".
>
> Can someone help me understanding?
> Thank's all, Aldo Stracquadanio.
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