Wrong image geometries reported by LibRaw 201910 snapshot?

[jconejero]

We are receiving bug reports like the following one after updating our RAW support module to LibRaw 201910 snapshot:

https://pixinsight.com/forum/index.php?topic=14206.0

It seems that some reported coordinates of the visible image region (the height, width, top_margin and left_margin members of libraw_image_sizes_t) are wrong. Currently we have several reports of users with Canon EOS 600D cameras, as the above bug report; I cannot confirm if the same happens with other cameras. Raw dimensions (raw_height, raw_width) are correct.

If this is a confirmed bug, can we have it fixed soon, please?

At any rate, thank you so much for your great work on LibRaw.

Juan Conejero
PixInsight Development Team
https://pixinsight.com/

[LibRaw]

This is not bug, but intentional (so won't be fixed).
The problem:
LibRaw::COLOR(row,col) operates in active area coordinates, (0,0) relates to (left_margin,top_margin) of entire sensor.
To make this call valid for both active area and entire sensor area, left_margin/top_margin are always made even for bayer images (and multiple of 6 for X-Trans images)

[jconejero]

Of course, that makes perfect sense. So we'll stick to the 201910 snapshot, and will recommend our users to repeat their image preprocessing tasks with the new version. Thank you.

[LibRaw]

BTW, crop area may change for any camera because of several causes:

• change in LibRaw for cameras w/ hardcoded crops
• change in LibRaw for specific vendor or model: switch from hardcoded crop to crop specified in metadata
• change (update) in camera firmware that results in metadata-recorded crop change.

So, for processing like 'dark fields', 'bias', 'flat fields', etc it always safer to save entire sensor area, not cropped area (and do crop on final stage)

[jconejero]

Thank you for the information. I didn't know that raw cropping areas can be subject to these variations.

We have an option to disable cropping in our RAW support module. However, it's true that most of our users don't enable it and prefer to crop the visible region automatically at the image calibration stage. I'll consider implementing a slightly more 'persuasive' option to invite them to work on the entire raw frames.