Polygonize a raster using GDAL JAVA bindings - passing raster pixel value to the resulting feature

Question

I have a raster GeoTIFF file with values from 0 to let's say 5. When I run gdal.polygonize (I'm working with JAVA and GDAL bindings to JAVA) on it, I get features with corresponding polygons.

The problem is that the value of the raster pixels are not passed anywhere and I lose the information about which polygon belongs to which value. Is there any way to store this information anywhere?

PS. Sorry if the question is not clear. This is my first experience with GIS world (and with advanced programming also to be honest :) )

Answer 1

Well it is a bit late but maybe there is someone else with this problem. There is the command gdalinfo . If you have pictures with only 1 band and a color palette you can use it to see which DN-code stands for wich RGB-Value. Here is an example of the code using the gdal java-bindings (gdal 1.11.1):

    public static void main(String[] args) {
        String[] src = { "C:\\Users\\User\\Desktop\\picture.png" };
        int[][] table = gdalInfo(src);
        System.out.println(table.length);
        System.out.println(Arrays.deepToString(table));

    }

    public static int[][] gdalInfo(String[] args) {
        gdal.AllRegister();

        args = gdal.GeneralCmdLineProcessor(args);

        Dataset hDataset = gdal.Open(args[0], gdalconstConstants.GA_ReadOnly);

        Band hBand = hDataset.GetRasterBand(1);
        ColorTable hTable = hBand.GetRasterColorTable();
        int[][] colorCodes = new int[hTable.GetCount()][3];

        if (hBand.GetRasterColorInterpretation() == gdalconstConstants.GCI_PaletteIndex
                && (hTable != null)) {

            for (int count = 0; count < hTable.GetCount(); count++) {

                colorCodes[count][0] = hTable.GetColorEntry(count).getRed();
                colorCodes[count][1] = hTable.GetColorEntry(count).getGreen();
                colorCodes[count][2] = hTable.GetColorEntry(count).getBlue();
            }

        }

        return colorCodes;
    }