Image Intensity
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Hi all, Can any one tel me the command in matlab to calculate the intensity of image.
2 个评论
Jean
2013-7-5
Does anyone further know how to do this for a specific area of pixels? For example, image(100:1:200,100:1:200) for a 100 by 100 pixel area, and get the intensity in this area as an average?
Image Analyst
2013-7-5
编辑:Walter Roberson
2014-2-11
meanGrayLevel = mean2(yourImage(100:200,100:200));
Don't use "image" as the name of your variable since it's a function.
采纳的回答
Image Analyst
2012-6-4
The mean of a particular pixel is just simply the pixel value, since there is only one sample - nothing really to take the mean of:
intensityValue = grayImage(100, 230);
meanIntensityValue = mean(grayImage(100, 230));
Here, of course meanIntensityValue will equal intensityValue.
To get the mean of all the pixel values in the entire image, you can do any of these:
meanIntensityValue = mean2(grayImage);
meanIntensityValue = mean(grayImage(:));
meanIntensityValue = mean(mean(grayImage));
13 个评论
Walter Roberson
2021-6-9
If you are using a grayscale image in which the values are "brightness" (as opposed to something like Hue), then the real unit would be closer to "brightness per pixel^2". Summing that over a number of pixels in a row or column would give you "brightness per pixel^2 * pixels" which would be "brightness per pixel".
... Brightness would not be the real physical unit. Eyes do not perceive brightness in a linear manner. https://www.pathwaylighting.com/products/downloads/brochure/technical_materials_1466797044_Linear+vs+Logarithmic+Dimming+White+Paper.pdf
"Approximate perceived brightness = sqrt(measured brightness)"
I just woke up, and digging into luminance and chromaticities and transfer functions this early in my day is making my brain hurt. @Image Analyst studied those things, so he would be in a much better position to talk about what the real physical units would be.
Image Analyst
2021-6-10
The usual nomenclature of your vertical profile (the image summed horizontally across columns) is "integrated gray value" and it will have units of gray levels. For a standard digital camera which measures illuminance Lux or irradiance (watts per square meter), the units of gray level correspond to units of energy (Joules).
(watts/m^2) * (area of pixel in m^2) * (seconds of exposure time) = joules.
Note that watts = joules/second so everything cancels out except for joules.
Note: units prefixed with "Phot" or "Lum" (like illuminance) refer to radiation in the visible range 400-700 nm. If it doesn't have a prefix or has "rad" prefix (like irradiance), then it applies to all energy across the whole electromagnetic spectrum.
更多回答(4 个)
swetha Derangula
2017-8-5
编辑:Walter Roberson
2017-8-5
Is this code correct for entire image intensity? I didn't get any intensity value
clear all;
close all;
o=imread('450.jpg');
i=rgb2gray(o);
imshow(i)
intensityValue = i(100, 230);
meanIntensityValue = mean(mean(i));
please suggets me
2 个评论
Walter Roberson
2017-8-5
No code that contains "clear all" can be correct.
Your line
intensityValue = i(100, 230);
extracts one particular pixel's intensity, and only that one pixel. However,
meanIntensityValue = mean(mean(i));
should be fine for taking the mean intensity of the entire image.
Adina Stoica
2012-6-4
Well, the intensity of the image is the average of the intensities of all pixels in an image (unless you're doing anything more specific than that). So if you do
mean(imagefile(:))
you should get the intensity of the image.
Saranya
2014-1-30
hi image analyst i want to measure the intensity profile for gray scale image.. can you help me..?
18 个评论
Rasika Devi
2017-3-21
编辑:Rasika Devi
2017-3-21
Thank you so much sir.. One more thing from that weight value,how do i perform the image segmentation by using any algorithm? kindly help me...
Walter Roberson
2017-3-21
I suggest you look in the File Exchange, for Image Analyst's Image Segmentation Tutorial
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