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2010-05-10T08:40:29  <yuguess> Hello sir
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2010-05-10T08:44:08  <kstreith> hello
2010-05-10T08:46:00  <yuguess> Hi, I have a problem about that tutorial 5
2010-05-10T08:46:19  <yuguess> The result of that algorithm should be a gray image
2010-05-10T08:46:34  <yuguess> while I find some pixel value is more than 255
2010-05-10T08:47:49  <yuguess> a little confused
2010-05-10T08:48:28  <tclarke> was the original data multi-byte?
2010-05-10T08:48:35  <tclarke> only 8-bit unsigned data will have a max value of 255
2010-05-10T08:50:00  <yuguess> Oh, the orignal data is signed short type
2010-05-10T08:50:34  <tclarke> also, the results of tutorial 5 are stored as floating point
2010-05-10T08:50:43  <tclarke> so in theory the values can be even larger...the current kernel will clamp however
2010-05-10T08:50:54  <tclarke> the histogram window controls how the actual data values are mapped to the 0-255 display values
2010-05-10T08:52:31  <tclarke> the default is to calculate a histogram for the data and set the value at the 5th percentile to 0 in the display, set the value at the 95th percentile to 255 in the display, and to linearly map the 5-95 values to the remaining display values
2010-05-10T08:52:53  <yuguess> sorry
2010-05-10T08:54:19  <yuguess> though the actual value of result may be larger than 255, it will finally mapped into  range 0~255 when displaying in the Opticks
2010-05-10T08:54:27  <kstreith> yuguess: myself and mconsidi heading out to lunch
2010-05-10T08:56:19  <yuguess> Ok
2010-05-10T08:58:21  <tclarke> correct
2010-05-10T08:58:36  <tclarke> if you open the Histogram Window, the shaded region will be mapped to 0-255. Things outside that region are clamped to 0 or 255
2010-05-10T08:58:45  <tclarke> and the mapping can be linear (the default), logarithmic, or exponential
2010-05-10T08:58:55  <tclarke> finally, it's also possible to perform histogram equalization in which case you won't see a shaded region
2010-05-10T09:03:06  <yuguess> yeah, I tried, when I adjust the shade range shorter, the image become "brighter"
2010-05-10T09:04:49  <yuguess> since fewer pixels are mapped into 0~255 and more are set to 255
2010-05-10T09:05:03  <tclarke> correct
2010-05-10T09:10:42  <yuguess> Thanks, I know how to solve my problem now : )
2010-05-10T10:33:32  <kstreith> back
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2010-05-10T19:58:16  <okibot> New news from nightlybuilds: Opticks4.4Dev-Nightly-Linux #14 (SUCCESS)
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