Counting color pixels
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Hi,
I am new to this forum but I'm having some difficulty with the ImageJ program. My goal is to take color doppler images and to count the colored pixels within a certain area. The main colors I am looking for are red and blue, but the color ranges from light to dark red and blue. What makes things difficult is that the background is black, light and dark grey. Basically I want to count the colored pixels and divide it by the total number of pixels of a chosen area. I keep seeing that this is possible with Image J, but I have not been able to make this work. Any help would be appreciated. Thank you! |
Antwort: Counting color pixels
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Hi Smileyy,
you might want to convert your image from regular RGB (what I assume you have) to a HUE based presentation. Here seems to be a good overview article of the color capabilities of several ImageJ plugins: http://www.fmhs.auckland.ac.nz/sms/biru/_docs/Colour_Analysis_Tools_in_ImageJ.pdf Mit freundlichen Grüßen / Best regards Joachim Wesner Smileyy1585 <[hidden email]> Gesendet von: An ImageJ Interest [hidden email] Group Kopie <[hidden email]. GOV> Thema Counting color pixels 12.09.2009 23:01 Bitte antworten an ImageJ Interest Group <[hidden email]. GOV> Hi, I am new to this forum but I'm having some difficulty with the ImageJ program. My goal is to take color doppler images and to count the colored pixels within a certain area. The main colors I am looking for are red and blue, but the color ranges from light to dark red and blue. What makes things difficult is that the background is black, light and dark grey. Basically I want to count the colored pixels and divide it by the total number of pixels of a chosen area. I keep seeing that this is possible with Image J, but I have not been able to make this work. Any help would be appreciated. Thank you! -- View this message in context: http://n2.nabble.com/Counting-color-pixels-tp3633831p3633831.html Sent from the ImageJ mailing list archive at Nabble.com. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ |
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In reply to this post by Smileyy1585
What is the format of your doppler images? If it is just 8-bit index
color e.g., NWS radar images, then it would be really easy. Select an area of interest. Do Analyze | Histogram, then click on List. The first column is the color index and the second column is the pixel count. Now you just need to find out what color is represented by which index value. You can zoom in and position the cursor on the pixel with the color you want to count and read it off on the status bar of ImageJ. It would be up to you to define what red or blue are e.g., range of dBZ you're interested in. Hope this help. On Sat, 12 Sep 2009, Smileyy1585 wrote: > I am new to this forum but I'm having some difficulty with the ImageJ > program. My goal is to take color doppler images and to count the colored > pixels within a certain area. The main colors I am looking for are red and > blue, but the color ranges from light to dark red and blue. What makes > things difficult is that the background is black, light and dark grey. > Basically I want to count the colored pixels and divide it by the total > number of pixels of a chosen area. > > I keep seeing that this is possible with Image J, but I have not been able > to make this work. Any help would be appreciated. Thank you! -- Pang (Wai Pang Chan, [hidden email], PAB A087, 206-685-1519) The Biology Imaging Facility (http://depts.washington.edu/if/) |
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In reply to this post by Smileyy1585
My guess is that you have not operationally defined what you mean by red and
blue. Computer images are composed of a 3 byte definition in the red, green, and blue channel which means that there will be shades of red and blue that may contain a small amount of green. Likewise, grey and white pixels can contain significant red and blue content. This makes your task potentially non-trivial even if the original red and blue colors were added using pseudocoloring values in the red and blue channels of the image. One of the first thing to do to get an idea of the problem you face is to do: iamge | color | split channels and examine the areas that were previously blue or red. The next thing that I would recommend is taking a look at Gabriel Landini's Threshhold_colour plugin described on the ImageJ Wiki, http://imagejdocu.tudor.lu/doku.php?id=plugin:color:threshold_colour:start and available on his site, http://www.dentistry.bham.ac.uk/landinig/software/software.html It may be that looking at your image in HSB mode will give you additional insight into how to segment it. HTH, Rob ----- Original Message ----- From: "Smileyy1585" <[hidden email]> To: <[hidden email]> Sent: Saturday, September 12, 2009 4:01 PM Subject: Counting color pixels > Hi, > > > I am new to this forum but I'm having some difficulty with the ImageJ > program. My goal is to take color doppler images and to count the colored > pixels within a certain area. The main colors I am looking for are red and > blue, but the color ranges from light to dark red and blue. What makes > things difficult is that the background is black, light and dark grey. > Basically I want to count the colored pixels and divide it by the total > number of pixels of a chosen area. > > I keep seeing that this is possible with Image J, but I have not been able > to make this work. Any help would be appreciated. Thank you! > -- > View this message in context: > http://n2.nabble.com/Counting-color-pixels-tp3633831p3633831.html > Sent from the ImageJ mailing list archive at Nabble.com. > |
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