imageMap-methods {Rgraphviz} | R Documentation

## Write an HTML IMG tag together with a MAP image map.

### Description

Write an HTML IMG tag together with a MAP image map.

### Usage

      ## S4 method for signature 'Ragraph, connection, list,
      ##   character':
      imageMap(object, con, tags, imgname, width, height, usr = par("usr"))

### Arguments

`object` | The graph layout for which we want to create an image map.
`con` | Connection to which the image map is written.
`tags` | Named list whose elements are named character vectors. Names must correspond to node names in `object`. See details.
`imgname` | Character. Name of the image file (for example PNG file) that contains the plot.
`width` | Width of the image.
`height` | Height of the image.
`usr` | Numeric vector of length 4. The user coordinates in the plot window that `object` was plotted into.

### Details

The most important tags are `TITLE`, `HREF`, and `TARGET`. If the list `tags` contains an element with name `TITLE`, then this must be a named character vector containing the tooltips that are to be displayed when the mouse moves over a node. The names of the nodes are specified in the `names` attribute of the character vector and must match those of `object`.

Similarly, `HREF` may be used to specify hyperlinks that the browser can follow when the mouse clicks on a node, and `TARGET` to specify the target browser window.

Currently, only rectangular regions are implemented; the actual shape of the nodes as specified in `object` is ignored. Also, tags for edges of the graph are currently not supported.

This function is typically used with the following sequence of steps:

1. Create a graph layout with `agopen`
2. Plot it into a bitmap device, e.g. `jpeg` or `png`.
3. Write HTML header.
4. Call the `imageMap` function.
5. Optionally, write further text into the HTML connection.
6. Close HTML file.

### Value

The function is called for its side effect, which is writing text into the connection `con`.

### Author(s)

Wolfgang Huber http://www.dkfz.de/mga/whuber

### See Also

`agopen`, `openHTMLpage`

### Examples

    fhtml = paste(tempfile(), ".html", sep="")
    fpng  =paste(tempfile(), ".png", sep="")

    if(capabilities()["png"] && interactive()) {

      ## Create and layout a random graph
      set.seed(123)
      g  = randomEGraph(letters[14:22], 0.2)
      lg = agopen(g, name="My layout")

      ## Make tooltips and hyperlinks
      tooltip = paste("This is node", nodes(g))
      url = paste("This could be a link for node", nodes(g))
      names(url) = names(tooltip) = nodes(g)

      ## Plot it
      width = height = 512
      png(fpng, width=width, height=height)
      par(mai=rep(0,4))
      plot(g)

      ## Write an HTML file with the image map
      con = file(fhtml, open="wt")
      writeLines("<html><head><title>Click Me</title></head><body>\n", con)

      imageMap(lg, con, fpng, tags=list(HREF=url, TITLE=tooltip), width=width, height=height)

      writeLines("</body></html>", con)
      dev.off()
      close(con)
      cat("Now have a look at file", fhtml, "with your browser.\n")
    }

[Package Rgraphviz version 1.8.0 Index]