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

weixj2003ld weixj2003ld at 163.com
Sun May 16 20:17:51 EDT 2010

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?


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
gdal_translate -b 1 -of PNG -ot Byte source.tif des.png
gdal_translate -b 1 -of PNG -ot UInt16 source.tif des.png
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.

Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/ 
17.2416N 80.1426E
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