Using two topic's information in a subscriber's callback

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Hi,

I have a design problem.

I have a topic with an image, that needs to be analyzed and I need to get a certain coordinate from it. I also have another topic with a certain coordinate.

I need to use both of those coordinates in a callback method. So let's say I have a subscriber's callback:

callback(imageInfo) {
    //I only get the imageinfo here
}

So I get the imageinfo there but I need to use the certain coordinate info also, to calculate a result. I could create a global variable for the certain coordinate and have a different subscriber with a callback setting its value and then use the global variable in the callback(imageinfo).

But is there a better way? It doesn't seem that good.