MQBBoxMin

Overview

MQBBoxMin (Median/Quantile Bounding Box) derives a robust subject bounding box from a mask. It auto-detects whether the mask represents foreground or background, applies quantile-based trimming to ignore outliers, and optionally inflates the result to maintain a minimum span. The node returns both the bounding box and a debug string describing the decision path.

Inputs

mask (MASK): Input tensor in any common mask layout; converted to a 2D float array internally.
invert_mask (STRING, default "auto"): Controls which side of the mask is treated as foreground. "auto" picks the side with less border mass, "false" keeps the mask as-is, "true" inverts it.
q_left, q_right, q_top, q_bottom (FLOAT, defaults 0.005 / 0.995): Quantiles used to crop the subject along each axis. Lower values trim only extreme borders; higher values create tighter boxes.
min_span_px (INT, default 8): Minimum width/height enforced after quantile cropping.
tight_crop (BOOLEAN, default False): When False, the node simply returns the full image bounds. When True, the node creates a tight bounding box around the subject with safety margins and crops to the tightest legal resolution, effectively cropping out dead space in the image.

Outputs

x, y, w, h (INT): Bounding box coordinates in pixels relative to the mask.
debug (STRING): Notes on the foreground selection, quantile bounds, and any aspect-ratio adjustments.

Processing Notes

The mask is normalised to [0, 1], with automatic conversion from 8-bit values when necessary.
Quantile bounds are computed using cumulative sums along rows and columns, ensuring consistent behaviour even for noisy masks.
The routine grows the quantile box by a padding proportional to image size and then searches for the minimal-area rectangle matching the image aspect ratio. Additional candidate aspect ratios (1:1, 2:3, 3:4, 9:16, etc.) are evaluated to minimise area.
If a suitable aspect container cannot be found, the raw quantile rectangle is returned.

Tips

Feed the output directly into FitAspectHeadSafe to generate camera-friendly crops.
Raise min_span_px when working with thin subject masks to avoid degenerate boxes.
For masks that include the background (white is background, black is subject), set invert_mask to "true" instead of relying on "auto".*** End Patch

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