MATLAB: Problem creating a geoTIFF from a non-georeferenced image

georeferencinggeotiffgeotiffwriteworldfilewrite

I'm trying to create a geoTIFF file in Matlab from the attached png. I'm following the example provided in: https://uk.mathworks.com/help/map/examples/exporting-images-and-raster-grids-to-geotiff.html
but need to create georeferencing information from scratch, so using makerefmat and worldfilewrite to acheive this. The code below does not cause a crash, but generates a TIFF that image readers seem to struggle with, so I assume I'm doing something wrong. There may also be some redundancy as I haven't worked with TIFF tags before. Any help appreciated!
% Load image without georeferencing
RGB = imread('uk_dT.png');
% Create worldfile for image.  At present this is done by first creating a
% reference matrix, then using these values to generate a worldfile.
% Longitude spans -17:10 (west to east), latitude 63:47 (north to south)
lonmin = -17; lonmax = 10; latmin = 47; latmax = 63;
DX = (lonmax-lonmin)/(length(RGB(1,:,1))); DY = (latmin-latmax)/(length(RGB(:,1,1)));
R = makerefmat(lonmin, latmax, DX, DY);
worldfilewrite(R,'uk_dT.tfw');
% Read worldfile, create geotiff
REF = worldfileread('uk_dT.tfw','geographic',size(RGB));
geotiffwrite('uk_dT.tif',RGB,REF)

Best Answer

file = 'uk_dT.png' ; 
[path,name,ext] = fileparts(file) ;
I = imread(file) ;
lonmin = -17; lonmax = 10; latmin = 47; latmax = 63;
x = linspace(lonmin,lonmax,size(I,2)) ;
y = linspace(latmin,latmax,size(I,1)) ;
% Write to geotiff
R = georasterref('RasterSize',size(I),'LatitudeLimits',[latmin,latmax],'LongitudeLimits',[lonmin,lonmax]);
tiffile = strcat(name,'.tif') ;
geotiffwrite(tiffile,I,R)
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