[gdal-dev] get different result when use different parameters

[Chaitanya kumar CH]

weixj2003ld,

Be aware that histogram equalization changes the pixel values. It is better
used for display purposes only.

You should choose between Byte and UInt16 or any other type based on the
range of pixel values in the raster band.

On Mon, May 17, 2010 at 5:47 AM, weixj2003ld <weixj2003ld at 163.com> wrote:

> Thk u for your answer.
> Yes,they give the same output except Type.
>
> Driver: PNG/Portable Network Graphics
> Files: SRTM_GTOPO_u30_n090e060.png
> Size is 4800, 6000
> Coordinate System is `'
> Corner Coordinates:
> Upper Left  (    0.0,    0.0)
> Lower Left  (    0.0, 6000.0)
> Upper Right ( 4800.0,    0.0)
> Lower Right ( 4800.0, 6000.0)
> Center      ( 2400.0, 3000.0)
> Band 1 Block=4800x1 Type=Byte, ColorInterp=Gray
> 1. I want to know that when I should use '-ot Byte ' and when use ' -ot
> UInt16 '?
> 2. when I use  -ot UInt16 ',Must I perform histogram equalization on it?
>
>
>
> weixj2003ld,
>
> I couldn't open the link.
> Try "gdalinfo -mm des.png" on both the output images. I think they will
> both give the same output. UInt16 should give a dark image unless you
> perform histogram equalization on it.
>
> 2010/5/11 weixj2003ld <weixj2003ld at 163.com>
>
>> I download a elevation data (SRTM,GTOPO30) from
>> http://glcfapp.glcf.umd.edu:8080/esdi/index.jsp
>>
>>  use
>> gdal_translate -b 1 -of PNG -ot Byte source.tif des.png
>> and
>> gdal_translate -b 1 -of PNG -ot UInt16 source.tif des.png
>> differently,
>> with parameter 'UInt16',I get a black picture,with Byte,get a different
>> one,why?
>> BTW,I want to get a png file from elevation data(.tif),must I use command
>> gdal_translate?
>> Thk u in advance.
>>
>>
>
>
>
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-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9848167848
17.2416N 80.1426E
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