Faster cycling through waves

Hello everybody,

I am currently implementing a thresholding algorithm in Igor. I want to decompose my original image wave in smaller section. A threshold will be applied to every single section. Afterwards I want to compose a new wave from the single smaller sections.

I am currently using two for loops in order to paste the smaller waves into the big output wave. See the example below:




However, my approach seem to be very slow. I was wondering if there is a faster way to assign values to a wave. Maybe something similar to pointers and iterators in C++?

Best regards,


Your existing code would go a bit faster by holding the dimsize outputs as variables and not calling them for every pixel.

You can also do the same thing without looping doing a direct wave assignment, like this(untested):

bigWave[rowOffset,rowOffset + (dimsize(SmallWave,0) - 1) ][colOffset,colOffset + (dimsize(SmallWave,1) - 1)] = smallWave[p-rowOffset][q-colOffset]

Where you specify the start and end of your pasted region and then assign the values from smallWave starting at [0][0].

But to answer the question, for this kind of stuff MatrixOp and the Image operations are very fast. e.g. I'm pretty sure one of the ImageTransform keywords is for a stitching operation that you might be able to use for your needs.

After you obtain the smaller image you can insert them into the larger image using ImageTransform with the keyword insertImage.

I don't know if your custom algorithm can use or accommodate to any of the inbuilt thresholding algorithms, but if it can, then something like this might be the fastest solution:

make/o/n=(256,256) w_img = ceil(enoise(256,2))

duplicate/o w_img, w_roi
redimension/b/u w_roi

fastop w_roi = 100 // any non zero value
w_roi[0,127][0,127] = 0 // define the roi
ImageThreshold/o/q/m=1/r=w_roi w_img // overwrite w_img due to the /o flag

fastop w_roi = 100
w_roi[128,255][128,255] = 0
ImageThreshold/o/q/m=1/r=w_roi w_img

This is the closes you'd get to operating on a region of the image wave without memory copy and duplication.