Extracting Bayer array from DNG file results in black image

CFA
1

I’m trying to get the Color Filter Array (CFA) from a DNG file using Matlab. I used some code I found online but it’s not working as expected. Here’s what I did:

imageInfo = imfinfo('camera_raw.dng');
tiff = Tiff('camera_raw.dng', 'r');
subIFDs = tiff.getTag('SubIFD');
tiff.setSubDirectory(subIFDs(1));
rawData = double(tiff.read());

When I plot rawData, it’s just a black image. The matrix is all zeros. I’m not sure what I’m doing wrong. Does anyone know how to correctly extract the Bayer array from a DNG file? I’d really appreciate some help figuring this out. Thanks!

2

I’ve encountered this problem before when working with DNG files. One crucial step you might be missing is applying the appropriate white balance and color correction to the raw data. The raw sensor data often appears dark or black without proper processing. Try incorporating these steps after reading the raw data:

Apply the white balance coefficients from the DNG metadata. Demosaic the Bayer pattern to get full RGB values. Apply the color matrix from the DNG metadata for color correction.

Additionally, ensure you’re reading the correct IFD (Image File Directory) that contains the raw sensor data. Some DNG files have multiple IFDs, and the raw data might not be in the first one. If you’re still having issues, consider using a dedicated raw processing library like LibRaw or dcraw, which handle many of these complexities automatically.

3

hey ryan, i’ve run into similar issues before. make sure ur DNG file isn’t compressed - some cameras do that by default. also, try using the ‘imread’ function instead of Tiff. it’s simpler and often works better for DNGs. if that doesn’t help, double-check ur file path and permissions. good luck!

4

Hey there! I’m super curious about your DNG processing adventure. Have you tried playing around with the exposure settings when you’re reading the file? Sometimes the raw data can be pretty dark and needs a boost.

Oh, and here’s a thought - what camera are you using? Different manufacturers handle their raw files slightly differently. Maybe we could dig into the specifics of your camera model?

I’m wondering, have you tried viewing the DNG in any other software? Like, does it look okay in Lightroom or RawTherapee? That might give us a clue if it’s a file issue or a code issue.

This stuff can be tricky, but it’s so cool when you finally crack it! Keep us posted on what you find out, okay? I’m really interested to see how you solve this!