As far as I can see your problem is that you decided to use JAI directly
instead of calculating NDVI using the GeoTools raster classes that would
have maintained the location of the data. JAI is an image processing
solution and as such throws away all the geography in the data - then
GeoTools is unable to import the image because it doesn't know where it is.
Ian
On 11 January 2013 11:37, Gökçen Güner <[email protected]> wrote:
> Thank you so much guys. I didn't have much time at that time so I switched
> from Geotools to Grass, I'm not familiar with Python as much as Java but it
> has more features on programming side.
>
> Besides I couldn't use geotools effectively, I think some native
> implementation required this image processing thing. It shouldn't be so
> hard to subtract an image from another. You just do it pixel by pixel, you
> have same geocode in both files, preserve them and write it to the new
> file, it is just easy as that. I looked at JAI related posts, 9 of 10
> people say 'don't use it'. I looked at Geotools posts or tutorials, they
> all use JAI. Geotools must find a way to get rid of JAI in my opinion.
>
> It is not directly about geotools, it is about Java for sure but any GIS
> framework should have a some way to do this. In Grass, they bridged
> functionalities of Grass to Python, you import the classes(modules in
> Python) and you are good to go. In image processing, C/C++ has more
> popularity in comparison with Java but using JNI it can be dealt with I
> think. It is not well documented you can say, it's hard do debug or test
> you can say but it should be considered as a solution. Coded with JNI,
> proposed as a Java class and users will use it.
>
> As a Java developer and fan(it is fun to code with java), I felt
> disappointed when I realized that in Java we don't have so many choices in
> GIS. Geotools still seems to be best but considering its competitors I
> think more work is needed.
>
> Thanks for making time to read this.
>
> 2013/1/10 Rafael Santos <[email protected]>
>
>> Hi,
>> > I need to find NDVI and other vegetation indices and then find changes
>> > in time with tif images.
>> >
>> > I've been using Geotools for this. Took 2 tiff images, then using QGis
>> > I changed them to PNG because original ones are huge. Then taking
>> > those 2 PNG I created NDVI image using JAI. The problem is that I
>> > couldn't show this file with Geotools. You can look at the code here:
>> That code creates a TIFF with floating point pixels, which can be
>> loaded/viewed with DisplayNBImage since DisplayNBImage internally
>> creates a byte-based surrogate version of the floating-point image. If
>> your purpose is just to display the image why not create a byte-based one?
>>
>> >
>> > In fact, proposing non-Jai way of the same thing would be awesome.
>> >
>> If you don't mind having a byte image that should be simple. Open both
>> images, declare a matrix of the appropriate size of type float,
>> calculate the NDVI for each pixel, create a temporary byte image and
>> populate it with the values from the matrix, properly normalized. Some
>> steps for this are on
>>
>> http://www.lac.inpe.br/JIPCookbook/1200-create-gl.jsp#imageanddatamanipulationcreatinggraylevelimages
>> . Two caveats: I am not sure if plain Java have readers for TIFF images
>> (in case your original images are TIFFs) and the original NDVI values
>> will be of course gone -- not an issue for visualization/comparison.
>>
>> hope it helps
>>
>> Rafael
>>
>>
>>
>>
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>
>
>
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Ian Turton
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