How to get vaules in the histogram

pzwhz · Post by **pzwhz** » Sun Mar 25, 2012 7:52 am

How to get values in the histogram from a script?
For example: Mean,Std Dev,Median,Pixels.

pfaffenbichler · Post by **pfaffenbichler** » Sun Mar 25, 2012 9:17 am

With mathematic, I guess.
At least I don’t know another way to access that information.

Maybe this helps somewhat:
Code: Select all// 2012, use it at your own risk;
#target photoshop
if (app.documents.length > 0) {
var myDocument = app.activeDocument;
var theHist = myDocument.histogram;
// get total number;
var thePixels = 0;
for (var m = 0; m < theHist.length; m++) {
thePixels = thePixels + theHist[m]
};
// get mean and median;
var theMean = 0;
var aTotal = 0;
var check = false;
for (var n = 0; n < theHist.length; n++) {
theMean = theMean + (n * theHist[n] / thePixels);
aTotal = aTotal + theHist[n];
if (aTotal >= thePixels / 2 && check == false) {
   theMedian = n;
   check = true;
   }
};
alert (thePixels + " pixels\n" + theMean + " mean\n" + theMedian + " median")
};

pzwhz · Post by **pzwhz** » Tue Mar 27, 2012 7:36 am

These code is to get the Histogram of whole document , how to get a layer's histograms? Like photoshop can select whole document or a layer selected .

pfaffenbichler · Post by **pfaffenbichler** » Tue Mar 27, 2012 7:45 am

The Document Object Model does not seem to provide a histogram-property for (art)layers.
So short of hiding all other layers and loading the layer’s transparency as a selection I can’t think of a (reasonable) method to get that.
Maybe one of the regulars knows more about it, though.

What is your ultimate target for this information anyway?

xbytor · Post by **xbytor** » Tue Mar 27, 2012 2:47 pm

Code: Select allSo short of hiding all other layers and loading the layer’s transparency as a selection I can’t think of a (reasonable) method to get that.

This is true. Also, the histogram is shallow, only 8 bits instead of 16 or 32. You are getting a rough approximation using Document.histogram regardless of what you do. There is a file in xtools that handles some of the maths needed but I've never figured a way to get exactly the numbers that show up in the histogram palette.

pzwhz · Post by **pzwhz** » Wed Mar 28, 2012 1:10 am

There are many artlayers in the document.
I want to get the histogram of a artlayer by name.
If the artlayer has transparent pixels, the best not statistics the transparent pixels.
Can you give me the script?

pfaffenbichler · Post by **pfaffenbichler** » Wed Mar 28, 2012 8:42 am

As xbytor has confirmed that a viable approach would be to hide the other Layers and load the transparency you could just try amending the Script accordingly yourself.