feat: add ADetailer support (#1785)

docs/adetailer.md

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+# ADetailer
+
+`sd-cli` can run a YOLOv8 object detector on an existing or newly generated
+image and perform a cropped inpaint pass for every detected object. The first
+implementation supports YOLOv8 detection checkpoints. YOLOv8 segmentation and
+MediaPipe models are not supported yet.
+
+## Convert a detector
+
+Ultralytics checkpoints must be converted before use. The converter fuses
+BatchNorm into convolution layers and writes a safetensors file with the weight
+names expected by the native GGML implementation.
+
+```bash
+python scripts/convert_yolov8_to_safetensors.py face_yolov8n.pt face_yolov8n.safetensors
+```
+
+The converter requires Python packages `ultralytics`, `torch`, and
+`safetensors`.
+Only YOLOv8 detection checkpoints are accepted.
+PyTorch checkpoints use pickle internally, so only convert `.pt` files from a
+trusted source.
+
+## Repair an existing image
+
+Use the dedicated `adetailer` mode to detect and repair objects in an existing
+image:
+
+```bash
+./bin/sd-cli \
+  -M adetailer \
+  -m model.safetensors \
+  -i input.png \
+  -o repaired.png \
+  -p "detailed portrait photo" \
+  --negative-prompt "deformed face" \
+  --steps 24 \
+  --cfg-scale 6 \
+  --strength 0.4 \
+  --sampling-method dpm++2m \
+  --scheduler karras \
+  --ad-model face_yolov8n.safetensors \
+  --extra-ad-args "confidence=0.3,inpaint_padding=32,mask_blur=4"
+```
+
+This mode reuses the normal image-generation options for the detail pass:
+
+- `--init-img`, `--output`, `--prompt`, and `--negative-prompt`
+- `--steps`, `--cfg-scale`, `--sampling-method`, and `--scheduler`
+- `--strength`, `--seed`, LoRA settings, VAE tiling, and backend assignments
+- `--width` and `--height`, which also resize the input when specified
+
+`--ad-prompt` and `--ad-negative-prompt` optionally override the normal prompts.
+Values provided in `--extra-ad-args`, such as `steps`, `cfg_scale`,
+`denoising_strength`, or `inpaint_width`, take precedence over inherited values.
+
+## Repair generated images
+
+ADetailer can also run automatically after normal image generation:
+
+```bash
+./bin/sd-cli \
+  -m model.safetensors \
+  -p "portrait photo" \
+  --ad-model face_yolov8n.safetensors \
+  --ad-prompt "[PROMPT], detailed face" \
+  --ad-negative-prompt "" \
+  --extra-ad-args "confidence=0.3,denoising_strength=0.4,inpaint_width=512,inpaint_height=512"
+```
+
+An empty ADetailer prompt inherits the main prompt. `[PROMPT]` inserts the main
+prompt, `[SEP]` assigns different prompts to consecutive masks, and `[SKIP]`
+skips the corresponding mask.
+
+All settings other than the detector path and prompts are passed through
+`--extra-ad-args` as a comma-separated `key=value` list:
+
+| Key | Default | Description |
+| --- | ---: | --- |
+| `input_size` | `640` | Square YOLO input size; must be a multiple of 32 |
+| `confidence` | `0.3` | Detection confidence threshold |
+| `nms` | `0.45` | NMS IoU threshold |
+| `max_detections` | `100` | Maximum detections retained after NMS |
+| `mask_k_largest` | `0` | Keep only the largest K masks; zero keeps all |
+| `mask_min_ratio` | `0` | Minimum bbox area relative to the image |
+| `mask_max_ratio` | `1` | Maximum bbox area relative to the image |
+| `dilate_erode` | `4` | Positive values dilate; negative values erode |
+| `x_offset`, `y_offset` | `0` | Mask offset in pixels; positive Y moves upward |
+| `mask_mode` | `none` | `none`, `merge`, or `merge_invert` |
+| `merge_masks`, `invert_mask` | `false` | Boolean alternatives to `mask_mode` |
+| `mask_blur` | `4` | Final composite feather radius |
+| `inpaint_padding` | `32` | Padding around the detected region |
+| `inpaint_width`, `inpaint_height` | mode-specific | `512x512` after generation; input/output size in `adetailer` mode |
+| `denoising_strength` | mode-specific | `0.4` after generation; inherits `--strength` in `adetailer` mode |
+| `steps` | `0` | Detail steps; zero inherits the main generation |
+| `cfg_scale` | `-1` | Detail CFG; a negative value inherits the main generation |
+| `sample_method` | inherited | Detail sampler name |
+| `scheduler` | inherited | Detail scheduler name |
+| `sort_by` | `none` | `none`, `left_to_right`, `center_to_edge`, or `area` |
+
+Multiple masks are processed serially. Each completed inpaint becomes the input
+for the next mask, and the seed is incremented by the mask index. Use
+`mask_mode=merge` to process all detections in one inpaint pass.
+
+The detector uses the `detector` backend module. For example, keep detection on
+the CPU while diffusion runs on CUDA:
+
+```bash
+--backend "diffusion=cuda0,detector=cpu"
+```