Generate HTML-Map from image

Question

Is there a way of automatically generating a HTML-Map compatible list of coordinates of polygon-like objects (e.g. countries on a map) with very distinctive borders?

Example image:

Map of CEE countries http://www.bankaustria.at/landkarten/CEE_2007_w524.jpg

Final output:

<map id ="ceemap" name="ceemap">
    <area shape="poly" coords="149,303,162,301,162,298,171,293,180,299,169,309,159,306,148,306,149,303" href="austria.html" target ="_blank" alt="Austria" />       
    <!-- ... -->
</map>

Any tools/scripts extracting the coordinates of a polygon-like selection would be helpful.

Answer 1

Thanks for your help!

Although Jonathans hint to use the Sobel filter definitely would work, I chose Sparrs approach of first converting the bitmap into a vector image (via Inkscape) and then processing the SVG file. After studying some of the basics of the SVG spec, it was pretty easy to extract the - for HTML image maps needed - X/Y coordinates from all the other junk and generate a suitable code.

Although it’s no rocket science, someone might find this piece of code useful:

// input format: M 166,362.27539 C 163.525,360.86029 161.3875,359.43192 161.25,359.10124 C ...
private static void Svg2map(string svg_input)
{
    StringBuilder stringToFile = new StringBuilder();

    // get rid of some spaces and characters
    var workingString = svg_input.Replace("z", "").Replace(" M ", "M").Replace(" C ", "C");
    // split into seperate polygons
    var polygons = workingString.Split('M');
    foreach (var polygon in polygons)
    {
        if (!polygon.Equals(String.Empty))
        {
            // each polygon is a clickable area
            stringToFile.Append("<area shape=\"poly\" coords=\"");
            // split into point information
            var positionInformation = polygon.Split('C');
            foreach (var position in positionInformation)
            {
                var noise = position.Trim().Split(' ');
                // only the first x/y-coordinates after C are relevant
                var point = noise[0].Split(',');
                foreach (var value in point)
                {
                    var valueParts = value.Split('.');
                    // remove part after comma - we don't need this accurancy in HTML
                    stringToFile.Append(valueParts[0]);
                    // comma for seperation - don't worry, we'll clean the last ones within an area out later
                    stringToFile.Append(",");
                }
            }
            stringToFile.AppendLine("\" href=\"targetpage.html\" alt=\"Description\" />");
        }
    }
    // clean obsolete commas - not pretty nor efficient
    stringToFile = stringToFile.Replace(",\"", "\"");

    var fs = new StreamWriter(new FileStream("output.txt", FileMode.Create));
    fs.Write(stringToFile.ToString());
    fs.Close();
}

Answer 2

Open the map in Inkscape. If it is a bitmap, use Path -> Trace Bitmap to trace the edges. Clean up the vector data to include only the paths that you want to appear in your imagemap. Save the document, I suggest to a POVRay file. Now you have a list of vertices (and plenty of markup or metadata that you don't care about) in a plain text format. Converting from that to the requisite HTML syntax is still a problem, but not nearly as complex as the first step.

For what it is worth, there is a long standing feature request for Inkscape to include an option to export HTML image maps.