| Re: Image output display from IDL [message #60822] |
Sat, 21 June 2008 16:31  |
Raghu
Messages: 3
Registered: June 2008
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Junior Member |
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On Jun 20, 3:51 pm, Yaswant Pradhan <Yaswant.Prad...@gmail.com> wrote:
> On Jun 20, 5:36 am, Raghu <geor...@gmail.com> wrote:
>
>
>
>
>
>> Hi Chris,
>
>> These are just gray scale images. I just narrowed down the actual
>> problem. My images are in ERDAS Imagine (.img) floating point data
>> type. When i convert these into floating point again using
>> float(images) in ENVI , the resulting images are in ENVI format. When
>> these ENVI float images are used in the script, the output looks fine.
>> It seems like IDL treats ERDAS' floats differently or i don't quite
>> know if there's something else thats wrong here. I have tried it a few
>> times now and although the header file in ENVI reads the ERDAS files
>> as float, the IDL script seems to do something else when i read the
>> ERDAS files directly.
>
>> I'm wondering if i'd have to import all my images into an IDL float
>> type before i start processing. I'd still think that float
>> irrespective of the software would be the same, but i might be wrong.
>
>> Ram
>
>> On Jun 19, 8:38 pm, Chris <cnb4s...@gmail.com> wrote:
>
>>> Are they truecolor images?
>
>>> If so, it may be an issue with how the image is passed back and forth
>>> in IDL. An n pixel by n pixel color image read into idl (usually) gets
>>> stored as a n x n x 3 data cube (plane 0 is R, plane 1 is G, and plane
>>> 2 is B). You have to tell IDL which dimension of the array stores
>>> these color slices when working with them. In the above example, the
>>> third dimension stores the color slices so, if I wanted to display the
>>> image in IDL, I would use tvscl,im,true=3. Similarly, if you write out
>>> a color image, you usually have to specify which dimension runs
>>> through the different colors. Perhaps during the reading and writing
>>> stages, you switched this index, meaning that the final image would
>>> have all of these weird color/stripe patterns.
>
>>> Try scanning the IDL help for the "TRUE" keyword
>
>>> Chris
>
>>> On Jun 19, 1:42 pm, Raghu <geor...@gmail.com> wrote:
>
>>>> Hi all,
>
>>>> I wrote a script in IDL which reads multiple images and outputs an
>>>> image according to some conditions i specified.
>>>> The code works, seemingly with no errors and outputs the required
>>>> image. However, when i display the image in ENVI, the output image
>>>> looks like a series of tiles/bands as if the values are grouped line-
>>>> by-line. The statistics are right, but the display looks really weird.
>
>>>> I had read something about how IDL stores images but i can't quite
>>>> find the keywords to search for it.
>>>> Does this have to do with any machine settings or is it a setting
>>>> within IDL itself ? Any ideas ?
>
>>>> I can attach a graphic if it helps.
>
>>>> Thanks in advance,
>>>> Ram- Hide quoted text -
>
>>> - Show quoted text -
>
> Unless you change the OS, IDL should treat the floating point grey-
> scale images (from ERDAS) correctly. Few points you could check - (i)
> number of pixels and scan-lines (and the size of the file), (ii) how
> the bands are stored, BIL/BSQ/BIP?
> If you are reading Erdas .img files straight in IDL, remember that
> there will be few bytes recorded as file header. Perhaps you want to
> export the images/bands as binary flat file(s) before reading in IDL.- Hide quoted text -
>
> - Show quoted text -
Hi,
It looks like IDL doesn't support ERDAS IMG files. It supports TIFF
and my program works with TIFF. As you said, i might have to import
the files into a compatible format before i read them in.
Thanks,
Ram
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