Legacy ImageMagick Discussions Archive

I have a series of raw format grayscale images, all with 12 bits per pixel. However, the pixels are padded with 4 bits in the MSBs, so that each pixel is 2 bytes long.

Is this the standard format for raw GRAY files? I can't seem to get IM to properly recognize these. For example, if I want to convert the image to a BMP, I've tried the following:

convert -size 4096x1714 -depth 12 gray:<input_file.raw> bmp:<output_file.bmp>

This doesn't output the correct image, and neither does using -depth 16.

What is the correct way to tell IM to handle 12-bit pixels, and do the samples need to be packed in the file, or can they be padded out to 16 bits?

Add -endian lsb or -endian msb along with -depth 16 and see if that fixes the problem.

I can see different results using the -endian option, but none of them are correct:

display -size 4096x1714 -depth 16 -endian msb gray:stem0.raw All black output
display -size 4096x1714 -depth 16 -endian lsb gray:stem0.raw Image shapes recognizable, but looks like MSBs and LSBs are swapped

display -size 4096x1714 -depth 12 -endian msb gray:stem0.raw Image shapes recognizable, but strong vertical striations
display -size 4096x1714 -depth 12 -endian lsb gray:stem0.raw Same as previous one


The pixels are stored big-endian, so I would expect that option to work, but something is still off. Any other ideas? Thanks!

We have a couple of ideas but to save time can you post a URL to one of your images and its width and height. We'll get it displayed properly and then post the proper command here.

You should have padded them in the lsb. Your "black" images may be really very dark gray,
with values 0-3855. To view the existing images you will have to multiply each pixel by 17.

Yes, that was the problem. These images were output from a software JPEG2000 decoder, and there was no option where to place the 12-bit samples inside the 16 bits (the MSBs were padded), so I had to rewrite the files myself in order to view them.

Then this was the correct command: display -size 4096x1714 -depth 16 -endian msb gray:input.raw gray:output.raw

It appears that the -depth option tells IM to always expect packed samples for a RAW pixel format. It would be useful if the documentation stated this, since I originally was confused whether to use -depth 12 or -depth 16.

Thanks for your assistance!