The new camera styles - question

[Bordwall]

Direct reading of an XMP file

This is a fairly hacky approach, but it’s possible to read the param values from the XML file by unpacking the binary data, provided you know the expected struct format. As a simple example, if you look at the source for the temperature module, you can find the definition for the dt_iop_temperature_params_t (link). This module simply stores four float values in the param struct. Finding the temperature operation element in the XML file for my test image, the param value is f3b420400000803f6a…

Here’s an earlier reply I wrote on decoding param values from sidecar xml files, and I expect it’s similar (if not identical) for styles. The struct for the exposure module can be found here in code.

Rather than updating the value in this way, it may be more straightforward to create a new style (based on the original) and make the change to the exposure module in the darktable UI.

Alternatively, you could create a style with your desired exposure settings and simply copy the parameter value from that file rather than encoding a new set “from scratch”.

Best of luck!