Image Histogram
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Hello everyone,
I am unable to understand why the max value is 255 in the graph shown below even when the graph is not reaching the maximum value? Kindly help... 
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Hello Chinmaya,
On 23.10.2014 16:13, csadangi wrote: > Hello everyone, > > I am unable to understand why the max value is 255 in the graph shown below > even when the graph is not reaching the maximum value? Kindly help... > <http://imagej.1557.x6.nabble.com/file/n5010164/2aa-acb.jpg> what makes you think there are no values of 255 in this image? Actually, all the pixels from the scale bar seem to be "white", in other words 255... Cheers Niko -- Niko Ehrenfeuchter | Image Analysis Specialist | Biozentrum, University of Basel | Klingelbergstr. 50/70 | CH-4056 Basel Phone: +41 (61) 26 72673 | [hidden email] | www.biozentrum.unibas.ch | www.microscopynetwork.unibas.ch -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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I didn't get your point on "Actually, all the pixels from the scale bar seem to be "white", in other words 255... " Could you please explain. I think there are no values of 255 in the image because the graph starts at 0 and ends way before 255. |
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In reply to this post by csadangi
That's the max value possible in a one channel color image. 0 = black 255
= white. This is a standard scale for 8bit gray images regardless of the content of the image On Oct 23, 2014 10:15 AM, "csadangi" <[hidden email]> wrote: > Hello everyone, > > I am unable to understand why the max value is 255 in the graph shown below > even when the graph is not reaching the maximum value? Kindly help... > <http://imagej.1557.x6.nabble.com/file/n5010164/2aa-acb.jpg> > > > > ----- > ---- > Chinmaya > Medical University Innsbruck > Innsbruck > Austria > -- > View this message in context: > http://imagej.1557.x6.nabble.com/Image-Histogram-tp5010164.html > Sent from the ImageJ mailing list archive at Nabble.com. > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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In reply to this post by csadangi
>
> I didn't get your point on "Actually, all the pixels from the scale bar seem > to be "white", in other > words 255... " Could you please explain. > > I think there are no values of 255 in the image because the graph starts at > 0 and ends way before 255. You're having a scale bar "stamped" into your image. And the pixels from this bar are white, meaning they are having a value of 255. At least that's my guess from the image you attached... Cheers Niko -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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In reply to this post by csadangi
The scalebar pixels are 255.
=========================================================================== Michael Cammer, Microscopy Core & Skirball Institute, NYU Langone Medical Center Cell: 914-309-3270 note that we do not receive messages left at 212-263-3208 http://ocs.med.nyu.edu/microscopy & http://microscopynotes.com/ -----Original Message----- From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of csadangi Sent: Thursday, October 23, 2014 10:13 AM To: [hidden email] Subject: Image Histogram Hello everyone, I am unable to understand why the max value is 255 in the graph shown below even when the graph is not reaching the maximum value? Kindly help... <http://imagej.1557.x6.nabble.com/file/n5010164/2aa-acb.jpg> ----- ---- Chinmaya Medical University Innsbruck Innsbruck Austria -- View this message in context: http://imagej.1557.x6.nabble.com/Image-Histogram-tp5010164.html Sent from the ImageJ mailing list archive at Nabble.com. -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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In reply to this post by Niko Ehrenfeuchter
Hi Chinmaya,
You might also want to see what you get if you select the "log" representation, or print out the list of values, by clicking on the "list" button. Joel Joel B. Sheffield, Ph.D Department of Biology Temple University Philadelphia, PA 19122 Voice: 215 204 8839 e-mail: [hidden email] URL: *http://tinyurl.com/khbouft <http://tinyurl.com/khbouft>* On Thu, Oct 23, 2014 at 10:23 AM, Niko Ehrenfeuchter < [hidden email]> wrote: > Hello Chinmaya, > > On 23.10.2014 16:13, csadangi wrote: > >> Hello everyone, >> >> I am unable to understand why the max value is 255 in the graph shown >> below >> even when the graph is not reaching the maximum value? Kindly help... >> <http://imagej.1557.x6.nabble.com/file/n5010164/2aa-acb.jpg> >> > > what makes you think there are no values of 255 in this image? > > Actually, all the pixels from the scale bar seem to be "white", in other > words 255... > > Cheers > Niko > > -- > Niko Ehrenfeuchter | Image Analysis Specialist | Biozentrum, University of > Basel | Klingelbergstr. 50/70 | CH-4056 Basel > Phone: +41 (61) 26 72673 | [hidden email] | > www.biozentrum.unibas.ch | www.microscopynetwork.unibas.ch > > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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This post was updated on .
Hi Prof. Joel,
Thanks a lot for the suggestion. I selected log and it shows there are points also at 255 and before that. And the list also shows points near 255 and before that too. Reading all the suggestions above i think it has also taken the scale bar (as it is white) in the calculation. I tried cropping the image by excluding the scale bar and i found that the maximum decreases to around 166. Thanks a lot :) Cheers
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Dear Chinmaya,
would you mind reading the ImageJ-Manual, especially page 141? <rsb.info.nih.gov/ij/docs/guide/user-guide.pdf> HTH Herbie :::::::::::::::::::::::::::::::::: On 23.10.14 18:09, csadangi wrote: > Hi Prof. Joel, > > Thanks a lot for the suggestion. > > I selected log and it shows there are points also at 255 and before that. > And the list also shows points near 255 and before that too. Reading all the > suggestions above i think it has also taken the scale bar (as it is white) > in the calculation. I tried cropping the image by excluding the scale bar > and i found that the maximum decreases to around 166. > Could you please tell me what does the "log" tells us? > > Thanks a lot :) > > Cheers > > > JOEL B. SHEFFIELD wrote >> Hi Chinmaya, >> >> You might also want to see what you get if you select the "log" >> representation, or print out the list of values, by clicking on the "list" >> button. >> >> Joel >> >> >> >> Joel B. Sheffield, Ph.D >> Department of Biology >> Temple University >> Philadelphia, PA 19122 >> Voice: 215 204 8839 >> e-mail: > >> jbs@ > >> URL: *http://tinyurl.com/khbouft <http://tinyurl.com/khbouft>* >> >> On Thu, Oct 23, 2014 at 10:23 AM, Niko Ehrenfeuchter < > >> nikolaus.ehrenfeuchter@ > >>> wrote: >> >>> Hello Chinmaya, >>> >>> On 23.10.2014 16:13, csadangi wrote: >>> >>>> Hello everyone, >>>> >>>> I am unable to understand why the max value is 255 in the graph shown >>>> below >>>> even when the graph is not reaching the maximum value? Kindly help... >>>> <http://imagej.1557.x6.nabble.com/file/n5010164/2aa-acb.jpg> >>>> >>> >>> what makes you think there are no values of 255 in this image? >>> >>> Actually, all the pixels from the scale bar seem to be "white", in other >>> words 255... >>> >>> Cheers >>> Niko >>> >>> -- >>> Niko Ehrenfeuchter | Image Analysis Specialist | Biozentrum, University >>> of >>> Basel | Klingelbergstr. 50/70 | CH-4056 Basel >>> Phone: +41 (61) 26 72673 | > >> nikolaus.ehrenfeuchter@ > >> | >>> www.biozentrum.unibas.ch | www.microscopynetwork.unibas.ch >>> >>> >>> -- >>> ImageJ mailing list: http://imagej.nih.gov/ij/list.html >>> >> >> -- >> ImageJ mailing list: http://imagej.nih.gov/ij/list.html > > > > > > ----- > ---- > Chinmaya > Medical University Innsbruck > Innsbruck > Austria > -- > View this message in context: http://imagej.1557.x6.nabble.com/Image-Histogram-tp5010164p5010173.html > Sent from the ImageJ mailing list archive at Nabble.com. > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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In reply to this post by csadangi
Hi Chinmaya,
There is a full description of the histogram function on the imageJ website: http://imagej.nih.gov/ij/docs/guide/146-30.html#toc-Subsection-30.10 Basically, though, the log display uses a log scale on the graph, so that small values appear to take up more space in the graph. Joel Joel B. Sheffield, Ph.D Department of Biology Temple University Philadelphia, PA 19122 Voice: 215 204 8839 e-mail: [hidden email] URL: *http://tinyurl.com/khbouft <http://tinyurl.com/khbouft>* On Thu, Oct 23, 2014 at 12:09 PM, csadangi <[hidden email]> wrote: > Hi Prof. Joel, > > Thanks a lot for the suggestion. > > I selected log and it shows there are points also at 255 and before that. > And the list also shows points near 255 and before that too. Reading all > the > suggestions above i think it has also taken the scale bar (as it is white) > in the calculation. I tried cropping the image by excluding the scale bar > and i found that the maximum decreases to around 166. > Could you please tell me what does the "log" tells us? > > Thanks a lot :) > > Cheers > > > JOEL B. SHEFFIELD wrote > > Hi Chinmaya, > > > > You might also want to see what you get if you select the "log" > > representation, or print out the list of values, by clicking on the > "list" > > button. > > > > Joel > > > > > > > > Joel B. Sheffield, Ph.D > > Department of Biology > > Temple University > > Philadelphia, PA 19122 > > Voice: 215 204 8839 > > e-mail: > > > jbs@ > > > URL: *http://tinyurl.com/khbouft <http://tinyurl.com/khbouft>* > > > > On Thu, Oct 23, 2014 at 10:23 AM, Niko Ehrenfeuchter < > > > nikolaus.ehrenfeuchter@ > > >> wrote: > > > >> Hello Chinmaya, > >> > >> On 23.10.2014 16:13, csadangi wrote: > >> > >>> Hello everyone, > >>> > >>> I am unable to understand why the max value is 255 in the graph shown > >>> below > >>> even when the graph is not reaching the maximum value? Kindly help... > >>> <http://imagej.1557.x6.nabble.com/file/n5010164/2aa-acb.jpg> > >>> > >> > >> what makes you think there are no values of 255 in this image? > >> > >> Actually, all the pixels from the scale bar seem to be "white", in other > >> words 255... > >> > >> Cheers > >> Niko > >> > >> -- > >> Niko Ehrenfeuchter | Image Analysis Specialist | Biozentrum, University > >> of > >> Basel | Klingelbergstr. 50/70 | CH-4056 Basel > >> Phone: +41 (61) 26 72673 | > > > nikolaus.ehrenfeuchter@ > > > | > >> www.biozentrum.unibas.ch | www.microscopynetwork.unibas.ch > >> > >> > >> -- > >> ImageJ mailing list: http://imagej.nih.gov/ij/list.html > >> > > > > -- > > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > > > > > > ----- > ---- > Chinmaya > Medical University Innsbruck > Innsbruck > Austria > -- > View this message in context: > http://imagej.1557.x6.nabble.com/Image-Histogram-tp5010164p5010173.html > Sent from the ImageJ mailing list archive at Nabble.com. > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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