Create fast intenstiy histogram without Vision toolkit

[Terry_S]

I am trying to create an intensity histogram from an 8bit gray scale image that is being acquired from a USB camera.  Using the drivers that camera that came with the camera I am able to get a 2D array of image data (1021 x 764).  What I am doing is concatenate all the columns in the array to create a 1d array.  I then use the general histogram function that is set to a max of 256, min of 0 and 100 bins.  This approach takes approx. 5 secs. to complete. Attached is my approach.

Is there a better approach that would process much faster? 

If I use the Vision functions to convert the image data to an IMAQ image and then using the IMAQ histograph function, it processes almost immediately.  However I do not wish to use the Vision functions because I do not wish to pay for a Vision runtime license for each installation of my application.

Thanks

Terry.

[RavensFan]

It looks like you are trying to do the same thing as Reshape Array.  If you used that function, how fast does it run?

[GregSands · Accepted solution]

This is the simplest way to obtain a histogram.  Is it fast enough?

That will give a 256-bin histogram, but I iust noticed that you want 100 bins for some reason.  The easiest way to do that is to scale your image from 0-255 to 0-99 (multiply by 99/255) and do the same thing, something like this:

[Terry_S]

Thanks for the suggestion GregS.  However the array function that you have in the inner for loop, where did you find this?  This is something I have not discovered yet in labview

[GregSands]

That's the In Place Element Structure, which ensures that the array is not copied when it is used.  You can find it in the Structures palette since LabVIEW 2009 I think.  Or you can effectively replace it with the pair of functions Array Index and Array Replace - the IPES is just a little cleaner!