Using JAI was not my decision, I couldn't find a JAI-free Geotools solution
for this as I said in my first post. I'll be glad to hear it.
2013/1/11 Ian Turton <[email protected]>
> 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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