Reading CR2 (Canon RAW) images into MATLAB

Hi,

I was wondering if anyone could help me to read in some CR2 images into MATLAB?

I have tried just using imread but it just reads the image as an 8 bit. I can used Adobe's DNG converter as people have suggested but would rather have the whole code automated. Other questions like this are a few years old so was hoping some people had new suggestions.

Thanks!

Answer 1

[Arvind Narayanan]

It is possible to read CR2 data into MATLAB with the normal workflow for reading images. You can try the following sample code snippet:

A=imread('sample.CR2');
imshow(A);
imwrite(A,'filename.jpg');

[Steffen B. Petersen]

The code below is essentially what Arvind proposes :

the red channel of the image displayed (an astronomical image with a few high intensity stars) is a correct representation of what MATLABN displayes - but clearly there is a problem with the lowest intensity levels of the image. It appears as if MATLAB is utilizing lossy compression schemes, which in apprearance looks like JPEG compression.

I would like to know how to swicth off the compression, if anybody knows.

[myfile,mypath]=uigetfile({'*.cr2'});

>> mygray2=myim(:,:,1);

>> mytiny2=mygray2(2000:2500,3300:3800);

>> figure(3);

>> imshow(mytiny2,[10 30]);

[DGM]

A CR2 file is structured like a TIFF. It contains multiple images, both compressed and uncompressed. Two of these images are JPG, only one of which is lossless (the CFA data). When picked up by imread(), it looks like it's just treating the image as a TIFF and reading the first IFD, which would be the lossy preview JPG.

Either use raw2rgb() to get a demosaiced RGB image from the CFA data, or use rawread() to get the CFA data to reconstruct the image yourself.

Otherwise, consider these resources.

Format information (see the resources at the end): http://lclevy.free.fr/cr2/

Processing RAW images in MATLAB: https://rcsumner.net/raw_guide/RAWguide.pdf

That guide PDF is fairly old, but the workflow it describes is essentially what you're avoiding by using raw2rgb().

Answer 2

[Dinesh Iyer]

The raw2rgb and rawread functions will support RAW file formats.

https://www.mathworks.com/help/images/ref/raw2rgb.html

https://www.mathworks.com/help/images/ref/rawread.html