Photoshop :: Histogram Pixel Area
Jun 15, 2011
For a research project, I am calculating the area of the cytosol of a cell by finding the total cell area and subtracting the total nuclear area. I have been using the lasso tool to select the boundaries and then the histogram to measure the total pixels in that selection area. Proportionately, the nuclear pixel area should always be smaller than the total cell area since the nucleus is inside that cell. Most of my measurements have been accurate, but I started to run into the problem in which occasionally the nuclear pixel area is larger the total cell area. This does not make sense, which means that Pixel # that the histogram records must not actually be counting every pixel. I have tried to do some reading online and it sounds like the histogram is made based on different color intensities. If that were the case, that histogram pixel count is not the total area of the selection but rather only the pixel count that is being used to calculate the histogram.
I have tried changing the Channels from grayscale to RGB, etc. to see if that might use more of the pixels but there is no difference. What is the difference in these measurements and how can I make sure that the histogram counts every pixel?
Also, once I have that issue figured out, to convert my pixel count to a cell area, do I use the equation
A=P/s^2?
A=real cell area
P=pixel count
S=linear pixel/cm.
I have a bar scale from the microscope on the bottom of each image, thus I can accurately find this variable. I would have to square it since I need the area. Does that look correct?
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Mar 22, 2012
I am using the histogram function in PS CS4 for Windows. I am using the magic wand tool to choose numerous "green" elements (for example). As I choose more and more elements, the pixel amount goes up in the histogram table. For some weird reason, when I choose enough elements to hit around 50000 pixels, the amount reverts to 12000 and goes to "cache level 2". I need to be able to have a total of all my elements for the project I'm working on. Is this a memory issue? How can I increase the cache?
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Jan 16, 2009
I am working on a research project that involves evaluating the relative abundance of various colors in a leaf. The leaves that I am working with have three distinct sections of color (green, burgundy, and coral).
I have scanned images of the leaf samples on a flat bed scanner (all with the same quality) and am using the magic wand tool to determine the total pixel count of the leaf and the total pixel count for each individual color. With this data, I determine the relative percent of each color within the leaf. Code:
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Jul 15, 2013
I am using Photoshop CS5.
Right now I am trying to extract edited area and add some effects only on the area. I added some hand paintings on a picture and I need to extract hand painted area from the picture and add some effects on the extracted hand paintings and combine it with the original picture. I know I should hand paint on a different layer and add some effects on the layer and combine it with the picture, but I have to do what I am doing right now.
See pictures below.(those pictures are much simpler than my pictures I am editing right now)
There is a layer that has only 1 color, green.And 2nd picture has pinky letter A on 1st layer, so 2nd layer has green and pink color. I need to extract pinky A letter from 2nd layer and need to add some effects only on the letter A, and combine 1st layer and edited letter A to make 3rd layer.
I tried to use blend mode Difference to extract edited area but it changes the color of the area.And I don't want to use select tool & alpha mask, because my picture is much complicated.
What I want to do is something like Difference Matte effect in After Effects. Is it possible in Photoshop?
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Aug 4, 2012
I have a layer with a vector mask.
When I go to the properties panel, enter the feather radius „0.5“ and hit the enter key it rounds it up to 1 (Pixels).
Entering „0.4“ and hitting enter gives 0.
4.3 gives 4
4.6 gives 5
and so on.
So hitting enter rounds the value, although decimal values are accepted and do work. Why is that? What's the purpose of rounding the number?
When I enter „0.5“ and click somewhere it works without changing it to 1. Then it's really just 0.5 px. But hitting enter (the most natural thing after entering some value) rounds it.
Is this a feature or a flaw?
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Apr 11, 2013
When I crop a picture Pixel Demensions become 6 bytes Width and Height 1 pixel each. I can no longer see the picture. How can I fix this?
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Apr 22, 2013
I have two art objects on two layers. I want to match to the pixel the two objects that otherwise could be exactly the same but one layered object was imported slightly smaller.
The scale tool has good scale handling, I just want to measure the tool spots to the pixel to gain an exact scale size factor and match sizes.
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May 12, 2007
It blows my mind that somthing this simple isnt all that simple. I used the eyedropper tool to slect a color from another photo, then used the brush while fully magnified to change the color of each pixel.
It was coming out a weird greyish color, and I noticed that if I clicked more than once, it got darker, but so did the pixels directly around the one i was editing. So, i copied both pictures, loaded them into paint, and went to town.
It worked, but then when i copied it back into photoshop, it had a black background (there was no background in the original pictures) around the sprite I was editing. I tried to use the magic wand tool to get rid of it, but it took parts of the sprite with it, so...
Is there any way that I can edit the color of a single pixel (or hell, even a group of pixels if they share the same exact color would be nice...preferred, even) accurately? If not, what program could I use that would keep the transparent background?
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Apr 11, 2008
Does anybody knows wich was the first PS version to include this window? silly question but I cant find it in version 7, I think the one with the eye in it´s logo.
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Jul 10, 2006
I sometimes see a razor
thin line on the right edge.
Is that clipping?
I mean it very clear when I see the mountain slamming up to the right, but many times I see a normal mountain rise and fall, and then seem to see this razor thin blue green or red line on the right edge.
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Feb 19, 2012
Via VBA macro, some way of getting RGB/CMYK color values of a bitmap pixel by pixel?
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May 22, 2012
about cs6 , why the histogram is always set to colors? i mean is a bug like cs5 it should be set by default to rgb
every photo i load it's always set to colors and i guess there is not option to save and have rgb by default.
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Feb 25, 2009
Other than using the PrtScrn procedure,
way to save/copy the histogram of an image?
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Mar 13, 2011
I managed to remove the background, of an image,(A whit background) and put the image on top of a transparent layer. made a transparent image. When I place this image over a light color background, it looks fine, but when I place it over a dark color background, the edge of the image looks very rough and dirty, I think it's because some of the anti alias from the original image, how can I make it a clean image without going to delete pixel by pixel?
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Jul 26, 2012
We are developing an application using functionality of Gimp´s channel mixer with java.
Our problem is that we don’t Know how channel mix works exactly for transforming pixel by pixel in Java.
For example,
We have an image an do on it the next mix:
Output Channel = Red
Red=200.0
Green=0.0
Blue=0.0
For simulate that, we transform all pixels with Red Component *2 and 255 (maximum) if is greater.
Our problem is:
Output Channel = Red
Red=200.0
Green=60.0
Blue=0.0
How can I simulate that?
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Oct 19, 2011
Why the histogram for a gradient is not flat, as I guess it should be? Or, how to make a gradient that results in a flat histogram (that is, with the same number of pixels for each level)? The screen capture annexed should clarify the subject.
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Nov 5, 2008
On a number of tutorials in Photoshop User and elsewhere I've noticed when the curves dialogue is brought up there's a histogram laid in the background of the curves manipulator, but I don't have that. How do I get that histogram? I use CS2.
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Feb 24, 2008
When using the Hide function on the Crop tool I understand the pixels are hidden and the info retained. My question is does the Histogram palette look at the 'big picture' on the Hide function, and the histograms in either Levels or Curves only look at what is visible?
I'm guessing this is so, but was wondering if someone could verify it. I ask because of the difference in the histograms when using Levels or Curves compared to the Histogram palette.
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Oct 30, 2008
How do I get Photoshop to open with floating windows and the histogram in compact RGB mode? I have to reset this every time I open a new photo. I can't believe how hard it is to change modes in the histogram.I have to undock it, change it to expanded view, change the mode, change it back to compact view and redock it. This made sense to someone? I tried saving the workspace.
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Feb 28, 2013
I am trying to collect the mean, median, and mode of the RGB color values for a lot of different images.. Instead of just exporting the histogram raw data, I would rather just export what you see in the 'statistics' window when you open the histogram window.
Also, if I just wanted to transcribe it myself, I am not even able to keep the histogram window open while typing the data in excel.. So I constantly have to click back and forth (or just get better memory)..
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Apr 24, 2012
I use the histogram feature in PS to figure out how many square feet of yarn I will use in a rug that I am making (I work as a rug designer). I am running into a problem with this which is scary because my numbers have to be accurate.
As an example, I may have a 9x12 (inch--this is later blown up to feet using a transparency) drawing. In the drawing there may be 45 organic looking shapes that will be green. I use the magic wand tool and choose all of these green shapes. What I am noticing is that once I get to a certain number (not always consistent) in the histogram reading it will all of a sudden change to a different number and go to (for example) Cache 3. Because of this I have no idea if my histogram reading is accurate.
Is this some sort of memory issue? How do I prevent this from happening so that I can get an accurate heading?
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Sep 10, 2012
I was investigating something else, and I saw something not working... I'm under the distinct impression that the Histogram panel should automatically update after every operation. Having the Histogram panel displayed full-time on the screen, it should always be up to date.
However, when I Dodge or Burn or even paint color on an image, the Histogram is not updating. If I select one of the History states I've just created, it updates.Consider this simple sequence of operations:
I'm able to reproduce this failure in Photoshop CS5 as well, BUT NOT IN CS4 (it updates in Photoshop CS4 after every painting operation), so clearly it's not a new bug, though somehow I've managed not to notice it in my years of using Photoshop CS5.
Is it broken like this for everyone in Photoshop CS5 and 6?Could this be some twisted attempt to try to optimize painting performance? If so, why isn't there an option to allow a user to request it to update on every operation on a fast computer with cores out the wazoo?
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Sep 9, 2012
I prefer leaving my histogram in Photoshop CS6 in RGB mode, yet everytime I close the program and re-open photoshop, it defaults to Colors when I open a new document. How to get it to retain the RGB readout as a default?
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Jul 10, 2012
I found out on cs5 there is a histogram equalizer with in hdr toning...I also found out that there are plugins for histogram equalizers. I did download one called kamflex it was ok but it was noisy. From my learned friends on this site can you recommend others and if so where is the best place to get them.
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Jan 5, 2013
I'm currently recording the median luminosity and standard deviation of luminosity values in various photographs. This has been an ongoing project so I've been working on it for probably the last 4 months. Today I resumed my work and had to go back and check a previous photo that I had already recorded luminosity values for and noticed that the luminosity values that I had originally recorded were different than the values I'm seeing today in the histogram.
The attached picture shows the histogram I'm using (and have been using since I started this project). It is showing a median luminosity and standard deviation of luminosity for a photo that originally gave me this median luminosity value: 75 and this standard deviation: 27.87
I accidentally changed some setting in photoshop that affected the luminosity readings, or if the luminosity values of a photo are estimated by photoshop and thus aren't always the same etc. ?
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Dec 6, 2012
I'm using Photoshop CS5 and as you can see on the picture below, when I set my grid line to every 1 px, grid doesn't match canvas pixel size.
Now I'm not able to draw sharp shapes using pen tool because even if I hold shift key everything gets blurry.
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Jan 9, 2009
Recently I noticed the histogram in PS4 displaying color channels instead of luminosity. And all three RGB colors seem to spike off the top of the window. Is there a way to only display the luminosity histogram curve? Also, how often would be considered normal to have to re-set preferences?
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Jun 16, 2013
How can I save my raw histogram data in order to export it to something like excel?
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Sep 30, 2013
Since I capture my images in RAW, when I open them in Adobe Camera RAW (via Elements 11), what information is displayed in the image and the histogram I see?
Is it showing me the jpeg created in the camera? If so, the jpeg settings in my camera are not only important in viewing the LCD and the histogram in my camera at the time of capture. They would also be important in viewing my image when it first opens in Adobe Camera RAW.
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Aug 8, 2011
I live in the American Southwest and during the summers here the light is very harsh, the skies are usually completely clear and there are few, if any, shadows at mid-day. A couple of days ago a large red-tailed hawk had landed on a tree near where I live and I had the chance to shoot a lot of (Canon 7D) RAW images of the hawk with the bright sky behind. After processing I found I was not happy with the way the photos came out with my usual photo software (Dxo and Elements , so I re-installed a copy of PSPP X3 on my computer and thought I would try to use layers to darken the sky without darkening the hawk (if I can figure out how to use layers...).
But I noticed that when I opened the histogram palette that there was no graph display other than what looked like a single stright line (with no width) in the center of the photo. I tried several other RAW photos and they were pretty much the same - sometimes empty, sometimes very, very small curves, but so low on the graph that it was easy to not even see them. I then tried some of the converted jpgs from Dxo and Elements 8 and they seemed OK. Visible histograms with normal height. The other software I have displays the RAW histograms normally. The distribution is not pleasant because there is such a bright background, but the curves are easily visible and of normal height. I began to wonder if there was some issue with PSPP X3 processing RAW Canon cr2 images that might be causing this problem for me.
My PSPP X3 is up to date with all service packs, but I can find nothing of this issue in the knowledgebase.
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Dec 24, 2012
My Histogram is always gone when opening Gimp. It says "recently closed" but I never close it. I want it to stay open the way it used to.
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