Question

How can I read the X and Y DPI information from an image using Matlab?
imfinfo doesnt seems to supply this information.

Thanks

Answer 1

Not all images have resolution information. It contained in EXIF (Exchangeable Image File Format) tags. Only JPEG and TIFF files may contain EXIF, it usually supplied by digital camera or scanner. If it’s there you can get it from IMFINFO output.

info = imfinfo(filename);
xres = info.XResolution;
yres = info.YResolution;
resunit = info.ResolutionUnit;

You can always check if those fields exist:

if isfield(info,'XResolution')
    ...
end

UPDATE:

As for BMP files, they have HorzResolution and VertResolution properties that represent resolution in pixels per meter according to BMP format standard. You can multiply those values by 0.0254 to get DPI (approximately).