source: issm/trunk-jpl/src/m/contrib/morlighem/modeldata/interpFromGeotiff.m@ 26701

function dataout = interpFromGeotiff(geotiffname,X,Y,nanValue),

if nargin < 4
        nanValue = 10^30;
end

usemap = 0;
if license('test','map_toolbox')==0,
        disp('WARNING: map toolbox not installed, trying house code');
        usemap = 0;
elseif license('checkout','map_toolbox')==0
        disp('WARNING: map toolbox not available (checkout failed), trying house code');
        usemap = 0;
end

if usemap,
        [data,R] = geotiffread(geotiffname);
        data=double(flipud(data));
        xdata=R.XLimWorld(1):R.DeltaX:R.XLimWorld(2); xdata=xdata(:);
        xdata =(xdata(1:end-1)+xdata(2:end))/2;
        ydata=R.YLimWorld(2):R.DeltaY:R.YLimWorld(1); ydata=flipud(ydata(:));
        ydata =(ydata(1:end-1)+ydata(2:end))/2;
else

        %Get image info
        Tinfo = imfinfo(geotiffname);
        N     = Tinfo(1).Width;
        M     = Tinfo(1).Height;
        dx    = Tinfo(1).ModelPixelScaleTag(1);
        dy    = Tinfo(1).ModelPixelScaleTag(2);
        minx  = Tinfo(1).ModelTiepointTag(4);
        maxy  = Tinfo(1).ModelTiepointTag(5);

        %Generate vectors
        xdata = minx + dx/2 + ((0:N-1).*dx);
        ydata = maxy - dy/2 - ((M  -1:-1:0).*dy);

        %Read image
        if 1
                assert(dx>0); assert(dy>0);
                ydata = fliplr(ydata);

                %Get pixels we are interested in
                offset=2;
                xmin=min(X(:)); xmax=max(X(:));
                posx=find(xdata<=xmax);
                id1x=max(1,find(xdata>=xmin,1)-offset);
                id2x=min(numel(xdata),posx(end)+offset);

                ymin=min(Y(:)); ymax=max(Y(:));
                posy=find(ydata>=ymin);
                id1y=max(1,find(ydata<=ymax,1)-offset);
                id2y=min(numel(ydata),posy(end)+offset);

                data  = double(imread(geotiffname,'PixelRegion',{[id1y,id2y],[id1x,id2x]}));
                xdata=xdata(id1x:id2x);
                ydata=ydata(id1y:id2y);
        else
                data=double(flipud(imread(geotiffname)));
        end
        if nanValue > 0
                data(find(abs(data)>=nanValue))=NaN;
        else 
                data(find(data<=nanValue))=NaN;
        end

end

dataout = InterpFromGrid(xdata,ydata,data,X,Y);
dataout(dataout==-9999)=NaN;