Not a complete walk through here but some quick thoughts to a post for assist on twitter. What they wanted was to turn geotiff tags into csv or xml.
If you have GDAL installed & who doesn’t these days a quick way to turn the gdalinfo info (tags) into xml is to convert raster to Virtual Raster (VRT). This is an xml representation of raster.
>> gdal_translate -of VRT [destination name with .vrt extension]
This is what you end up with:
All that’s left to do is parse 
<VRTDataset rasterXSize=”5529″ rasterYSize=”4607″>
<SRS>PROJCS["Lambert Conformal Conic",GEOGCS["NAD83",DATUM["North_American_Datum_1983",SPHEROID["GRS 1980",6378137,298.2572221010002,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433],AUTHORITY["EPSG","4269"]],PROJECTION["Lambert_Conformal_Conic_2SP"],PARAMETER["standard_parallel_1",49],PARAMETER["standard_parallel_2",77],PARAMETER["latitude_of_origin",63.390675],PARAMETER["central_meridian",-91.86666666666666],PARAMETER["false_easting",6200000],PARAMETER["false_northing",3000000],UNIT["metre",1,AUTHORITY["EPSG","9001"]]]</SRS>
<GeoTransform> 5.6058900000000000e+06, 3.0000000000000000e+01, 0.0000000000000000e+00, 3.8967900000000000e+06, 0.0000000000000000e+00, -3.0000000000000000e+01</GeoTransform>
<Metadata>
<MDI key=”AREA_OR_POINT”>Area</MDI>
</Metadata>
<VRTRasterBand dataType=”Float32″ band=”1″>
<Metadata>
<MDI key=”COLOR_TABLE_RULE_RGB_0″>0.000000e+00 4.821725e+01 255 255 0 0 255 0</MDI>
<MDI key=”COLOR_TABLE_RULE_RGB_1″>4.821725e+01 9.643450e+01 0 255 0 0 255 255</MDI>
<MDI key=”COLOR_TABLE_RULE_RGB_2″>9.643450e+01 1.446518e+02 0 255 255 0 0 255</MDI>
<MDI key=”COLOR_TABLE_RULE_RGB_3″>1.446518e+02 1.928690e+02 0 0 255 255 0 255</MDI>
<MDI key=”COLOR_TABLE_RULE_RGB_4″>1.928690e+02 2.410863e+02 255 0 255 255 0 0</MDI>
<MDI key=”COLOR_TABLE_RULES_COUNT”>5</MDI>
</Metadata>
<NoDataValue>-9.99900000000000E+03</NoDataValue>
<ColorInterp>Gray</ColorInterp>
<SimpleSource>
<SourceFilename relativeToVRT=”1″>cded_30m.tif</SourceFilename>
<SourceBand>1</SourceBand>
<SourceProperties RasterXSize=”5529″ RasterYSize=”4607″ DataType=”Float32″ BlockXSize=”5529″ BlockYSize=”1″ />
<SrcRect xOff=”0″ yOff=”0″ xSize=”5529″ ySize=”4607″ />
<DstRect xOff=”0″ yOff=”0″ xSize=”5529″ ySize=”4607″ />
</SimpleSource>
</VRTRasterBand>
</VRTDataset>
