How can I save a 32 bit image (uint32) as a tiff?
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Hello,
I am currently working on a post processing HDR script which requires that I use a 32 bit data type. The images start at 14 bit, once they are imported I convert them to int32, and after I do my calculations I convert them back to uint32. After I create my HDR image the max pixel value is about 181,000 counts. I am currently using,
imwrite(FinalImage, 'HDR Result.tif')
which works for 16 bit images, but does not seem to work for 32 bit images. If you could give me any help or insight I would greatly appreciate it.
Thank you, Jason
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Ashish Uthama
2014-1-28
Could you say more on what you mean by 'does not seem to work'? Do you get an error message or does it write the data incorrectly?
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DGM
2024-6-6
Here's a simple demo that should demonstrate writing odd numeric classes to a TIFF. This supports 8,16, and 32 bit signed and unsigned integers, as well as single and double-precision float. Bear in mind that many things in IPT and base MATLAB may not properly deal with int8, int32, or uint32 images, so you're on your own.
% an uint8 image
inpict = imread('peppers.png'); % uint8, RGB
% inpict = im2gray(inpict); % if you want to play with signed-int types, RGB is not supported
% make it into a 32b integer class somehow
% normally, i'd just use MIMT imcast(), but let's just do this garbage
%inpict = imcast(inpict,'uint32'); % let's pretend we can't have nice things
inpict = uint32(inpict)*16843009; % uint8 to uint32
%inpict = int32(double(inpict)*16843009 - 2147483648); % uint8 to int32
% output file name
filename = 'test.tiff';
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% get to work
sz = size(inpict,1:3);
inclass = class(inpict);
t = Tiff(filename, 'w');
tagstruct.ImageLength = sz(1);
tagstruct.ImageWidth = sz(2);
tagstruct.Compression = Tiff.Compression.AdobeDeflate;
tagstruct.SamplesPerPixel = sz(3);
tagstruct.PlanarConfiguration = Tiff.PlanarConfiguration.Chunky;
% I/RGB?
% i'm choosing to presume that 3ch inputs are RGB
if sz(3) == 1
tagstruct.Photometric = Tiff.Photometric.MinIsBlack;
elseif sz(3) == 3
tagstruct.Photometric = Tiff.Photometric.RGB;
end
% what is the numeric type?
if isinteger(inpict) && inclass(1) == 'u'
tagstruct.SampleFormat = Tiff.SampleFormat.UInt;
elseif isinteger(inpict) && inclass(1) == 'i'
tagstruct.SampleFormat = Tiff.SampleFormat.Int;
elseif isfloat(inpict)
tagstruct.SampleFormat = Tiff.SampleFormat.IEEEFP;
else
error('this demo only supports integer and float inputs')
end
% what's the sample width?
switch inclass
case {'uint8','int8'}
tagstruct.BitsPerSample = 8;
case {'uint16','int16'}
tagstruct.BitsPerSample = 16;
case {'uint32','int32','single'}
tagstruct.BitsPerSample = 32;
case {'uint64','int64'}
error('LibTIFF does not support 64b outputs except for double-precision floats')
case 'double'
tagstruct.BitsPerSample = 64;
otherwise
error('this demo only supports integer and float inputs')
end
% write everything and close the file
t.setTag(tagstruct);
t.write(inpict);
t.close();
% read the image back
newpict = imread(filename);
isequal(inpict,newpict) % test that it's the same
Limitations:
- I have made no attempt to support logical images
- AFAIK, uint64/int64 inputs are not supported by LibTIFF. There may be broader reasons for that.
- Signed integer inputs cannot be RGB.
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