Add ImageToDisc pipeline step for saving processed images to file

[Copilot]

Adds a pipeline-compatible class to export intermediate images (raw, background, corrected, segmented) to disk for visualization and manual review.

pyopia.io.ImageToDisc

• Configurable image_keys selecting which pipeline data to save (default: imraw, imbg, im_corrected, imbw)
• scale_factor for downscaling before save
• collage mode: combine all stages into a single image, or save separately
• image_format selection (default: png)
• Gracefully skips missing keys

Usage

[steps.saveimages]
pipeline_class = 'pyopia.io.ImageToDisc'
output_folder = 'processed_images'
image_keys = ['imraw', 'im_corrected', 'imbw']
scale_factor = 0.5
collage = true

Tests

7 new tests covering separate/collage modes, scaling, grayscale, binary masks, and missing keys.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Means to store the background corrected images to file</issue_title>
<issue_description>featrue to direct background corrected images from an image stack to a "bckg-processed-folder".
These images are good for client visualisation and for manual review-
</issue_description>

<agent_instructions>Provide a command line function to store to file the various processed images in the pipeline to a file (from the raw image, background image, up til segmented image). Optional command inputs to scale down the size when storing to file, and whether to store one collage of image (per input image), or separate for each pipeline step. </agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Means to store the background corrected images to file #362

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[nepstad]

@copilot Update documentation with an instructive example of how and when to use this functionality

[Copilot]

@copilot Update documentation with an instructive example of how and when to use this functionality

Added documentation in commit 77618d4:

• docs/notebooks/toml_config.ipynb: New "Saving processed images to disc" section with a configuration options table, examples for both separate-image and collage modes, and guidance on where to place the step in the pipeline.
• docs/notebooks/processing_raw_data.ipynb: New "(Optional) Save intermediate images to disc" section in the processing guide, explaining when and how to use ImageToDisc for quality control.