How to set or update plot_brush points programmatically?

[filpas]

I am using the interactive plots and brushing in a few shiny app to select a region on an image or to zoom a particular region. I would like to implement dynamic zooming using plot brushing similar like zooming on cell phones and was wondering if its possible to set the plot_brush xmin, xmax, ymin, ymax programmatically. So far, I could not find a way to accomplish this.

The following simplified function should clarify the idea more:

dynamicZooming <- function(image) {
    p <- input$plot_brush
    image <- image[p$xmin-10:p$xmax+10, p$ymin-10:p$ymax+10]
    main_plot<- renderImage(image)
    output$plot_brush$xmin <- 10
    output$plot_brush$xmax <- dim(image)[1] - 10
    output$plot_brush$ymin <- 10
    output$plot_brush$ymax <- dim(image)[2] - 10
}