<span dir="ltr">weixj2003ld,<br><br>Be aware that histogram equalization changes the pixel values. It is better used for display purposes only.<br><br>You should choose between Byte and UInt16 or any other type based on the range of pixel values in the raster band.<br>
</span><br><div class="gmail_quote">On Mon, May 17, 2010 at 5:47 AM, weixj2003ld <span dir="ltr"><<a href="mailto:weixj2003ld@163.com">weixj2003ld@163.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>Thk u for your answer.</div>
<div>Yes,they give the same output except Type.</div>
<div> </div>
<div>Driver: PNG/Portable Network Graphics<br>Files: SRTM_GTOPO_u30_n090e060.png<br>Size is 4800, 6000<br>Coordinate System is `'<br>Corner Coordinates:<br>Upper Left ( 0.0, 0.0)<br>Lower Left ( 0.0, 6000.0)<br>
Upper Right ( 4800.0, 0.0)<br>Lower Right ( 4800.0, 6000.0)<br>Center ( 2400.0, 3000.0)<br>Band 1 Block=4800x1 Type=Byte, ColorInterp=Gray<br></div>
<div>1. I want to know that when I should use '-ot Byte ' and when use ' -ot UInt16 '?</div>
<div>2. when I use -ot UInt16 ',Must I perform histogram equalization on it?</div>
<div> </div>
<div> </div>
<div></div><br>
<blockquote style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;"><div class="im">weixj2003ld,<br><br>I couldn't open the link.<br>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.<br>
<br>
<div class="gmail_quote">2010/5/11 weixj2003ld <span dir="ltr"><<a href="mailto:weixj2003ld@163.com" target="_blank">weixj2003ld@163.com</a>></span><br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>I download a elevation data (SRTM,GTOPO30) from <a href="http://glcfapp.glcf.umd.edu:8080/esdi/index.jsp" target="_blank">http://glcfapp.glcf.umd.edu:8080/esdi/index.jsp</a></div>
<div> </div>
<div> use </div>
<div>gdal_translate -b 1 -of PNG -ot Byte source.tif des.png</div>
<div>and </div>
<div>gdal_translate -b 1 -of PNG -ot UInt16 source.tif des.png</div>
<div>differently,</div>
<div>with parameter 'UInt16',I get a black picture,with Byte,get a different one,why?</div>
<div>BTW,I want to get a png file from elevation data(.tif),must I use command gdal_translate?</div>
<div>Thk u in advance.</div>
<div> </div></blockquote></div><br></div></blockquote><br><br><span title="neteasefooter"></span><hr>
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