Create a mask image using the rectangle, then use the mask over the input image. Then apply the threshold. You can also extract and do that. as far i know, there is no way to apply only to the part of image directly.
Thats true. You will have only the extracted part left as a new image. If you need to place it on original image, you can use Image to Image vi. But remember that your thresholded part will be of binary and the other will be 8 bit. Usually this will be used only for diaplay purpose. Example attached.
To eat with the image on which it is drawn Rectangle. To me it is necessary to make Threshold only to Rectangle, instead of to the image. A problem in that that I on an output want to see the image together with Threshold. After application of a mask the image decreases on size Rectangle. As to me it to make.
Look my example. Yours it not that that is necessary to me. The same effect with rectangle. In my example the image is necessary for me does not vary, and you cut out Rectangle. Have removed a part of the first image. The problem to not cut out - to impose result Threeshold but not on the image. Only on Rectangle. At me on the image.
