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---
name: segment-anything-model
description: Foundation model for image segmentation with zero-shot transfer. Use when you need to segment any object in images using points, boxes, or masks as prompts, or automatically generate all object masks in an image.
version: 1.0.0
author: Orchestra Research
license: MIT
dependencies: [segment-anything, transformers>=4.30.0, torch>=1.7.0]
metadata:
hermes:
tags: [Multimodal, Image Segmentation, Computer Vision, SAM, Zero-Shot]
---
# Segment Anything Model (SAM)
Comprehensive guide to using Meta AI's Segment Anything Model for zero-shot image segmentation.
## When to use SAM
**Use SAM when:**
- Need to segment any object in images without task-specific training
- Building interactive annotation tools with point/box prompts
- Generating training data for other vision models
- Need zero-shot transfer to new image domains
- Building object detection/segmentation pipelines
- Processing medical, satellite, or domain-specific images
**Key features:**
- **Zero-shot segmentation**: Works on any image domain without fine-tuning
- **Flexible prompts**: Points, bounding boxes, or previous masks
- **Automatic segmentation**: Generate all object masks automatically
- **High quality**: Trained on 1.1 billion masks from 11 million images
- **Multiple model sizes**: ViT-B (fastest), ViT-L, ViT-H (most accurate)
- **ONNX export**: Deploy in browsers and edge devices
**Use alternatives instead:**
- **YOLO/Detectron2**: For real-time object detection with classes
- **Mask2Former**: For semantic/panoptic segmentation with categories
- **GroundingDINO + SAM**: For text-prompted segmentation
- **SAM 2**: For video segmentation tasks
## Quick start
### Installation
```bash
# From GitHub
pip install git+https://github.com/facebookresearch/segment-anything.git
# Optional dependencies
pip install opencv-python pycocotools matplotlib
# Or use HuggingFace transformers
pip install transformers
```
### Download checkpoints
```bash
# ViT-H (largest, most accurate) - 2.4GB
wget https://dl.fbaipublicfiles.com/segment_anything/sam_vit_h_4b8939.pth
# ViT-L (medium) - 1.2GB
wget https://dl.fbaipublicfiles.com/segment_anything/sam_vit_l_0b3195.pth
# ViT-B (smallest, fastest) - 375MB
wget https://dl.fbaipublicfiles.com/segment_anything/sam_vit_b_01ec64.pth
```
### Basic usage with SamPredictor
```python
import numpy as np
from segment_anything import sam_model_registry, SamPredictor
# Load model
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
sam.to(device="cuda")
# Create predictor
predictor = SamPredictor(sam)
# Set image (computes embeddings once)
image = cv2.imread("image.jpg")
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
predictor.set_image(image)
# Predict with point prompts
input_point = np.array([[500, 375]]) # (x, y) coordinates
input_label = np.array([1]) # 1 = foreground, 0 = background
masks, scores, logits = predictor.predict(
point_coords=input_point,
point_labels=input_label,
multimask_output=True # Returns 3 mask options
)
# Select best mask
best_mask = masks[np.argmax(scores)]
```
### HuggingFace Transformers
```python
import torch
from PIL import Image
from transformers import SamModel, SamProcessor
# Load model and processor
model = SamModel.from_pretrained("facebook/sam-vit-huge")
processor = SamProcessor.from_pretrained("facebook/sam-vit-huge")
model.to("cuda")
# Process image with point prompt
image = Image.open("image.jpg")
input_points = [[[450, 600]]] # Batch of points
inputs = processor(image, input_points=input_points, return_tensors="pt")
inputs = {k: v.to("cuda") for k, v in inputs.items()}
# Generate masks
with torch.no_grad():
outputs = model(**inputs)
# Post-process masks to original size
masks = processor.image_processor.post_process_masks(
outputs.pred_masks.cpu(),
inputs["original_sizes"].cpu(),
inputs["reshaped_input_sizes"].cpu()
)
```
## Core concepts
### Model architecture
```
SAM Architecture:
┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐
│ Image Encoder │────▶│ Prompt Encoder │────▶│ Mask Decoder │
│ (ViT) │ │ (Points/Boxes) │ │ (Transformer) │
└─────────────────┘ └─────────────────┘ └─────────────────┘
│ │ │
Image Embeddings Prompt Embeddings Masks + IoU
(computed once) (per prompt) predictions
```
### Model variants
| Model | Checkpoint | Size | Speed | Accuracy |
|-------|------------|------|-------|----------|
| ViT-H | `vit_h` | 2.4 GB | Slowest | Best |
| ViT-L | `vit_l` | 1.2 GB | Medium | Good |
| ViT-B | `vit_b` | 375 MB | Fastest | Good |
### Prompt types
| Prompt | Description | Use Case |
|--------|-------------|----------|
| Point (foreground) | Click on object | Single object selection |
| Point (background) | Click outside object | Exclude regions |
| Bounding box | Rectangle around object | Larger objects |
| Previous mask | Low-res mask input | Iterative refinement |
## Interactive segmentation
### Point prompts
```python
# Single foreground point
input_point = np.array([[500, 375]])
input_label = np.array([1])
masks, scores, logits = predictor.predict(
point_coords=input_point,
point_labels=input_label,
multimask_output=True
)
# Multiple points (foreground + background)
input_points = np.array([[500, 375], [600, 400], [450, 300]])
input_labels = np.array([1, 1, 0]) # 2 foreground, 1 background
masks, scores, logits = predictor.predict(
point_coords=input_points,
point_labels=input_labels,
multimask_output=False # Single mask when prompts are clear
)
```
### Box prompts
```python
# Bounding box [x1, y1, x2, y2]
input_box = np.array([425, 600, 700, 875])
masks, scores, logits = predictor.predict(
box=input_box,
multimask_output=False
)
```
### Combined prompts
```python
# Box + points for precise control
masks, scores, logits = predictor.predict(
point_coords=np.array([[500, 375]]),
point_labels=np.array([1]),
box=np.array([400, 300, 700, 600]),
multimask_output=False
)
```
### Iterative refinement
```python
# Initial prediction
masks, scores, logits = predictor.predict(
point_coords=np.array([[500, 375]]),
point_labels=np.array([1]),
multimask_output=True
)
# Refine with additional point using previous mask
masks, scores, logits = predictor.predict(
point_coords=np.array([[500, 375], [550, 400]]),
point_labels=np.array([1, 0]), # Add background point
mask_input=logits[np.argmax(scores)][None, :, :], # Use best mask
multimask_output=False
)
```
## Automatic mask generation
### Basic automatic segmentation
```python
from segment_anything import SamAutomaticMaskGenerator
# Create generator
mask_generator = SamAutomaticMaskGenerator(sam)
# Generate all masks
masks = mask_generator.generate(image)
# Each mask contains:
# - segmentation: binary mask
# - bbox: [x, y, w, h]
# - area: pixel count
# - predicted_iou: quality score
# - stability_score: robustness score
# - point_coords: generating point
```
### Customized generation
```python
mask_generator = SamAutomaticMaskGenerator(
model=sam,
points_per_side=32, # Grid density (more = more masks)
pred_iou_thresh=0.88, # Quality threshold
stability_score_thresh=0.95, # Stability threshold
crop_n_layers=1, # Multi-scale crops
crop_n_points_downscale_factor=2,
min_mask_region_area=100, # Remove tiny masks
)
masks = mask_generator.generate(image)
```
### Filtering masks
```python
# Sort by area (largest first)
masks = sorted(masks, key=lambda x: x['area'], reverse=True)
# Filter by predicted IoU
high_quality = [m for m in masks if m['predicted_iou'] > 0.9]
# Filter by stability score
stable_masks = [m for m in masks if m['stability_score'] > 0.95]
```
## Batched inference
### Multiple images
```python
# Process multiple images efficiently
images = [cv2.imread(f"image_{i}.jpg") for i in range(10)]
all_masks = []
for image in images:
predictor.set_image(image)
masks, _, _ = predictor.predict(
point_coords=np.array([[500, 375]]),
point_labels=np.array([1]),
multimask_output=True
)
all_masks.append(masks)
```
### Multiple prompts per image
```python
# Process multiple prompts efficiently (one image encoding)
predictor.set_image(image)
# Batch of point prompts
points = [
np.array([[100, 100]]),
np.array([[200, 200]]),
np.array([[300, 300]])
]
all_masks = []
for point in points:
masks, scores, _ = predictor.predict(
point_coords=point,
point_labels=np.array([1]),
multimask_output=True
)
all_masks.append(masks[np.argmax(scores)])
```
## ONNX deployment
### Export model
```bash
python scripts/export_onnx_model.py \
--checkpoint sam_vit_h_4b8939.pth \
--model-type vit_h \
--output sam_onnx.onnx \
--return-single-mask
```
### Use ONNX model
```python
import onnxruntime
# Load ONNX model
ort_session = onnxruntime.InferenceSession("sam_onnx.onnx")
# Run inference (image embeddings computed separately)
masks = ort_session.run(
None,
{
"image_embeddings": image_embeddings,
"point_coords": point_coords,
"point_labels": point_labels,
"mask_input": np.zeros((1, 1, 256, 256), dtype=np.float32),
"has_mask_input": np.array([0], dtype=np.float32),
"orig_im_size": np.array([h, w], dtype=np.float32)
}
)
```
## Common workflows
### Workflow 1: Annotation tool
```python
import cv2
# Load model
predictor = SamPredictor(sam)
predictor.set_image(image)
def on_click(event, x, y, flags, param):
if event == cv2.EVENT_LBUTTONDOWN:
# Foreground point
masks, scores, _ = predictor.predict(
point_coords=np.array([[x, y]]),
point_labels=np.array([1]),
multimask_output=True
)
# Display best mask
display_mask(masks[np.argmax(scores)])
```
### Workflow 2: Object extraction
```python
def extract_object(image, point):
"""Extract object at point with transparent background."""
predictor.set_image(image)
masks, scores, _ = predictor.predict(
point_coords=np.array([point]),
point_labels=np.array([1]),
multimask_output=True
)
best_mask = masks[np.argmax(scores)]
# Create RGBA output
rgba = np.zeros((image.shape[0], image.shape[1], 4), dtype=np.uint8)
rgba[:, :, :3] = image
rgba[:, :, 3] = best_mask * 255
return rgba
```
### Workflow 3: Medical image segmentation
```python
# Process medical images (grayscale to RGB)
medical_image = cv2.imread("scan.png", cv2.IMREAD_GRAYSCALE)
rgb_image = cv2.cvtColor(medical_image, cv2.COLOR_GRAY2RGB)
predictor.set_image(rgb_image)
# Segment region of interest
masks, scores, _ = predictor.predict(
box=np.array([x1, y1, x2, y2]), # ROI bounding box
multimask_output=True
)
```
## Output format
### Mask data structure
```python
# SamAutomaticMaskGenerator output
{
"segmentation": np.ndarray, # H×W binary mask
"bbox": [x, y, w, h], # Bounding box
"area": int, # Pixel count
"predicted_iou": float, # 0-1 quality score
"stability_score": float, # 0-1 robustness score
"crop_box": [x, y, w, h], # Generation crop region
"point_coords": [[x, y]], # Input point
}
```
### COCO RLE format
```python
from pycocotools import mask as mask_utils
# Encode mask to RLE
rle = mask_utils.encode(np.asfortranarray(mask.astype(np.uint8)))
rle["counts"] = rle["counts"].decode("utf-8")
# Decode RLE to mask
decoded_mask = mask_utils.decode(rle)
```
## Performance optimization
### GPU memory
```python
# Use smaller model for limited VRAM
sam = sam_model_registry["vit_b"](checkpoint="sam_vit_b_01ec64.pth")
# Process images in batches
# Clear CUDA cache between large batches
torch.cuda.empty_cache()
```
### Speed optimization
```python
# Use half precision
sam = sam.half()
# Reduce points for automatic generation
mask_generator = SamAutomaticMaskGenerator(
model=sam,
points_per_side=16, # Default is 32
)
# Use ONNX for deployment
# Export with --return-single-mask for faster inference
```
## Common issues
| Issue | Solution |
|-------|----------|
| Out of memory | Use ViT-B model, reduce image size |
| Slow inference | Use ViT-B, reduce points_per_side |
| Poor mask quality | Try different prompts, use box + points |
| Edge artifacts | Use stability_score filtering |
| Small objects missed | Increase points_per_side |
## References
- **[Advanced Usage](references/advanced-usage.md)** - Batching, fine-tuning, integration
- **[Troubleshooting](references/troubleshooting.md)** - Common issues and solutions
## Resources
- **GitHub**: https://github.com/facebookresearch/segment-anything
- **Paper**: https://arxiv.org/abs/2304.02643
- **Demo**: https://segment-anything.com
- **SAM 2 (Video)**: https://github.com/facebookresearch/segment-anything-2
- **HuggingFace**: https://huggingface.co/facebook/sam-vit-huge

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# Segment Anything Advanced Usage Guide
## SAM 2 (Video Segmentation)
### Overview
SAM 2 extends SAM to video segmentation with streaming memory architecture:
```bash
pip install git+https://github.com/facebookresearch/segment-anything-2.git
```
### Video segmentation
```python
from sam2.build_sam import build_sam2_video_predictor
predictor = build_sam2_video_predictor("sam2_hiera_l.yaml", "sam2_hiera_large.pt")
# Initialize with video
predictor.init_state(video_path="video.mp4")
# Add prompt on first frame
predictor.add_new_points(
frame_idx=0,
obj_id=1,
points=[[100, 200]],
labels=[1]
)
# Propagate through video
for frame_idx, masks in predictor.propagate_in_video():
# masks contains segmentation for all tracked objects
process_frame(frame_idx, masks)
```
### SAM 2 vs SAM comparison
| Feature | SAM | SAM 2 |
|---------|-----|-------|
| Input | Images only | Images + Videos |
| Architecture | ViT + Decoder | Hiera + Memory |
| Memory | Per-image | Streaming memory bank |
| Tracking | No | Yes, across frames |
| Models | ViT-B/L/H | Hiera-T/S/B+/L |
## Grounded SAM (Text-Prompted Segmentation)
### Setup
```bash
pip install groundingdino-py
pip install git+https://github.com/facebookresearch/segment-anything.git
```
### Text-to-mask pipeline
```python
from groundingdino.util.inference import load_model, predict
from segment_anything import sam_model_registry, SamPredictor
import cv2
# Load Grounding DINO
grounding_model = load_model("groundingdino_swint_ogc.pth", "GroundingDINO_SwinT_OGC.py")
# Load SAM
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
predictor = SamPredictor(sam)
def text_to_mask(image, text_prompt, box_threshold=0.3, text_threshold=0.25):
"""Generate masks from text description."""
# Get bounding boxes from text
boxes, logits, phrases = predict(
model=grounding_model,
image=image,
caption=text_prompt,
box_threshold=box_threshold,
text_threshold=text_threshold
)
# Generate masks with SAM
predictor.set_image(image)
masks = []
for box in boxes:
# Convert normalized box to pixel coordinates
h, w = image.shape[:2]
box_pixels = box * np.array([w, h, w, h])
mask, score, _ = predictor.predict(
box=box_pixels,
multimask_output=False
)
masks.append(mask[0])
return masks, boxes, phrases
# Usage
image = cv2.imread("image.jpg")
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
masks, boxes, phrases = text_to_mask(image, "person . dog . car")
```
## Batched Processing
### Efficient multi-image processing
```python
import torch
from segment_anything import SamPredictor, sam_model_registry
class BatchedSAM:
def __init__(self, checkpoint, model_type="vit_h", device="cuda"):
self.sam = sam_model_registry[model_type](checkpoint=checkpoint)
self.sam.to(device)
self.predictor = SamPredictor(self.sam)
self.device = device
def process_batch(self, images, prompts):
"""Process multiple images with corresponding prompts."""
results = []
for image, prompt in zip(images, prompts):
self.predictor.set_image(image)
if "point" in prompt:
masks, scores, _ = self.predictor.predict(
point_coords=prompt["point"],
point_labels=prompt["label"],
multimask_output=True
)
elif "box" in prompt:
masks, scores, _ = self.predictor.predict(
box=prompt["box"],
multimask_output=False
)
results.append({
"masks": masks,
"scores": scores,
"best_mask": masks[np.argmax(scores)]
})
return results
# Usage
batch_sam = BatchedSAM("sam_vit_h_4b8939.pth")
images = [cv2.imread(f"image_{i}.jpg") for i in range(10)]
prompts = [{"point": np.array([[100, 100]]), "label": np.array([1])} for _ in range(10)]
results = batch_sam.process_batch(images, prompts)
```
### Parallel automatic mask generation
```python
from concurrent.futures import ThreadPoolExecutor
from segment_anything import SamAutomaticMaskGenerator
def generate_masks_parallel(images, num_workers=4):
"""Generate masks for multiple images in parallel."""
# Note: Each worker needs its own model instance
def worker_init():
sam = sam_model_registry["vit_b"](checkpoint="sam_vit_b_01ec64.pth")
return SamAutomaticMaskGenerator(sam)
generators = [worker_init() for _ in range(num_workers)]
def process_image(args):
idx, image = args
generator = generators[idx % num_workers]
return generator.generate(image)
with ThreadPoolExecutor(max_workers=num_workers) as executor:
results = list(executor.map(process_image, enumerate(images)))
return results
```
## Custom Integration
### FastAPI service
```python
from fastapi import FastAPI, File, UploadFile
from pydantic import BaseModel
import numpy as np
import cv2
import io
app = FastAPI()
# Load model once
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
sam.to("cuda")
predictor = SamPredictor(sam)
class PointPrompt(BaseModel):
x: int
y: int
label: int = 1
@app.post("/segment/point")
async def segment_with_point(
file: UploadFile = File(...),
points: list[PointPrompt] = []
):
# Read image
contents = await file.read()
nparr = np.frombuffer(contents, np.uint8)
image = cv2.imdecode(nparr, cv2.IMREAD_COLOR)
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
# Set image
predictor.set_image(image)
# Prepare prompts
point_coords = np.array([[p.x, p.y] for p in points])
point_labels = np.array([p.label for p in points])
# Generate masks
masks, scores, _ = predictor.predict(
point_coords=point_coords,
point_labels=point_labels,
multimask_output=True
)
best_idx = np.argmax(scores)
return {
"mask": masks[best_idx].tolist(),
"score": float(scores[best_idx]),
"all_scores": scores.tolist()
}
@app.post("/segment/auto")
async def segment_automatic(file: UploadFile = File(...)):
contents = await file.read()
nparr = np.frombuffer(contents, np.uint8)
image = cv2.imdecode(nparr, cv2.IMREAD_COLOR)
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
mask_generator = SamAutomaticMaskGenerator(sam)
masks = mask_generator.generate(image)
return {
"num_masks": len(masks),
"masks": [
{
"bbox": m["bbox"],
"area": m["area"],
"predicted_iou": m["predicted_iou"],
"stability_score": m["stability_score"]
}
for m in masks
]
}
```
### Gradio interface
```python
import gradio as gr
import numpy as np
# Load model
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
predictor = SamPredictor(sam)
def segment_image(image, evt: gr.SelectData):
"""Segment object at clicked point."""
predictor.set_image(image)
point = np.array([[evt.index[0], evt.index[1]]])
label = np.array([1])
masks, scores, _ = predictor.predict(
point_coords=point,
point_labels=label,
multimask_output=True
)
best_mask = masks[np.argmax(scores)]
# Overlay mask on image
overlay = image.copy()
overlay[best_mask] = overlay[best_mask] * 0.5 + np.array([255, 0, 0]) * 0.5
return overlay
with gr.Blocks() as demo:
gr.Markdown("# SAM Interactive Segmentation")
gr.Markdown("Click on an object to segment it")
with gr.Row():
input_image = gr.Image(label="Input Image", interactive=True)
output_image = gr.Image(label="Segmented Image")
input_image.select(segment_image, inputs=[input_image], outputs=[output_image])
demo.launch()
```
## Fine-Tuning SAM
### LoRA fine-tuning (experimental)
```python
from peft import LoraConfig, get_peft_model
from transformers import SamModel
# Load model
model = SamModel.from_pretrained("facebook/sam-vit-base")
# Configure LoRA
lora_config = LoraConfig(
r=16,
lora_alpha=32,
target_modules=["qkv"], # Attention layers
lora_dropout=0.1,
bias="none",
)
# Apply LoRA
model = get_peft_model(model, lora_config)
# Training loop (simplified)
optimizer = torch.optim.AdamW(model.parameters(), lr=1e-4)
for batch in dataloader:
outputs = model(
pixel_values=batch["pixel_values"],
input_points=batch["input_points"],
input_labels=batch["input_labels"]
)
# Custom loss (e.g., IoU loss with ground truth)
loss = compute_loss(outputs.pred_masks, batch["gt_masks"])
loss.backward()
optimizer.step()
optimizer.zero_grad()
```
### MedSAM (Medical imaging)
```python
# MedSAM is a fine-tuned SAM for medical images
# https://github.com/bowang-lab/MedSAM
from segment_anything import sam_model_registry, SamPredictor
import torch
# Load MedSAM checkpoint
medsam = sam_model_registry["vit_b"](checkpoint="medsam_vit_b.pth")
medsam.to("cuda")
predictor = SamPredictor(medsam)
# Process medical image
# Convert grayscale to RGB if needed
medical_image = cv2.imread("ct_scan.png", cv2.IMREAD_GRAYSCALE)
rgb_image = np.stack([medical_image] * 3, axis=-1)
predictor.set_image(rgb_image)
# Segment with box prompt (common for medical imaging)
masks, scores, _ = predictor.predict(
box=np.array([x1, y1, x2, y2]),
multimask_output=False
)
```
## Advanced Mask Processing
### Mask refinement
```python
import cv2
from scipy import ndimage
def refine_mask(mask, kernel_size=5, iterations=2):
"""Refine mask with morphological operations."""
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (kernel_size, kernel_size))
# Close small holes
closed = cv2.morphologyEx(mask.astype(np.uint8), cv2.MORPH_CLOSE, kernel, iterations=iterations)
# Remove small noise
opened = cv2.morphologyEx(closed, cv2.MORPH_OPEN, kernel, iterations=iterations)
return opened.astype(bool)
def fill_holes(mask):
"""Fill holes in mask."""
filled = ndimage.binary_fill_holes(mask)
return filled
def remove_small_regions(mask, min_area=100):
"""Remove small disconnected regions."""
labeled, num_features = ndimage.label(mask)
sizes = ndimage.sum(mask, labeled, range(1, num_features + 1))
# Keep only regions larger than min_area
mask_clean = np.zeros_like(mask)
for i, size in enumerate(sizes, 1):
if size >= min_area:
mask_clean[labeled == i] = True
return mask_clean
```
### Mask to polygon conversion
```python
import cv2
def mask_to_polygons(mask, epsilon_factor=0.01):
"""Convert binary mask to polygon coordinates."""
contours, _ = cv2.findContours(
mask.astype(np.uint8),
cv2.RETR_EXTERNAL,
cv2.CHAIN_APPROX_SIMPLE
)
polygons = []
for contour in contours:
epsilon = epsilon_factor * cv2.arcLength(contour, True)
approx = cv2.approxPolyDP(contour, epsilon, True)
polygon = approx.squeeze().tolist()
if len(polygon) >= 3: # Valid polygon
polygons.append(polygon)
return polygons
def polygons_to_mask(polygons, height, width):
"""Convert polygons back to binary mask."""
mask = np.zeros((height, width), dtype=np.uint8)
for polygon in polygons:
pts = np.array(polygon, dtype=np.int32)
cv2.fillPoly(mask, [pts], 1)
return mask.astype(bool)
```
### Multi-scale segmentation
```python
def multiscale_segment(image, predictor, point, scales=[0.5, 1.0, 2.0]):
"""Generate masks at multiple scales and combine."""
h, w = image.shape[:2]
masks_all = []
for scale in scales:
# Resize image
new_h, new_w = int(h * scale), int(w * scale)
scaled_image = cv2.resize(image, (new_w, new_h))
scaled_point = (point * scale).astype(int)
# Segment
predictor.set_image(scaled_image)
masks, scores, _ = predictor.predict(
point_coords=scaled_point.reshape(1, 2),
point_labels=np.array([1]),
multimask_output=True
)
# Resize mask back
best_mask = masks[np.argmax(scores)]
original_mask = cv2.resize(best_mask.astype(np.uint8), (w, h)) > 0.5
masks_all.append(original_mask)
# Combine masks (majority voting)
combined = np.stack(masks_all, axis=0)
final_mask = np.sum(combined, axis=0) >= len(scales) // 2 + 1
return final_mask
```
## Performance Optimization
### TensorRT acceleration
```python
import tensorrt as trt
import pycuda.driver as cuda
import pycuda.autoinit
def export_to_tensorrt(onnx_path, engine_path, fp16=True):
"""Convert ONNX model to TensorRT engine."""
logger = trt.Logger(trt.Logger.WARNING)
builder = trt.Builder(logger)
network = builder.create_network(1 << int(trt.NetworkDefinitionCreationFlag.EXPLICIT_BATCH))
parser = trt.OnnxParser(network, logger)
with open(onnx_path, 'rb') as f:
if not parser.parse(f.read()):
for error in range(parser.num_errors):
print(parser.get_error(error))
return None
config = builder.create_builder_config()
config.max_workspace_size = 1 << 30 # 1GB
if fp16:
config.set_flag(trt.BuilderFlag.FP16)
engine = builder.build_engine(network, config)
with open(engine_path, 'wb') as f:
f.write(engine.serialize())
return engine
```
### Memory-efficient inference
```python
class MemoryEfficientSAM:
def __init__(self, checkpoint, model_type="vit_b"):
self.sam = sam_model_registry[model_type](checkpoint=checkpoint)
self.sam.eval()
self.predictor = None
def __enter__(self):
self.sam.to("cuda")
self.predictor = SamPredictor(self.sam)
return self
def __exit__(self, *args):
self.sam.to("cpu")
torch.cuda.empty_cache()
def segment(self, image, points, labels):
self.predictor.set_image(image)
masks, scores, _ = self.predictor.predict(
point_coords=points,
point_labels=labels,
multimask_output=True
)
return masks, scores
# Usage with context manager (auto-cleanup)
with MemoryEfficientSAM("sam_vit_b_01ec64.pth") as sam:
masks, scores = sam.segment(image, points, labels)
# CUDA memory freed automatically
```
## Dataset Generation
### Create segmentation dataset
```python
import json
def generate_dataset(images_dir, output_dir, mask_generator):
"""Generate segmentation dataset from images."""
annotations = []
for img_path in Path(images_dir).glob("*.jpg"):
image = cv2.imread(str(img_path))
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
# Generate masks
masks = mask_generator.generate(image)
# Filter high-quality masks
good_masks = [m for m in masks if m["predicted_iou"] > 0.9]
# Save annotations
for i, mask_data in enumerate(good_masks):
annotation = {
"image_id": img_path.stem,
"mask_id": i,
"bbox": mask_data["bbox"],
"area": mask_data["area"],
"segmentation": mask_to_rle(mask_data["segmentation"]),
"predicted_iou": mask_data["predicted_iou"],
"stability_score": mask_data["stability_score"]
}
annotations.append(annotation)
# Save dataset
with open(output_dir / "annotations.json", "w") as f:
json.dump(annotations, f)
return annotations
```

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# Segment Anything Troubleshooting Guide
## Installation Issues
### CUDA not available
**Error**: `RuntimeError: CUDA not available`
**Solutions**:
```python
# Check CUDA availability
import torch
print(torch.cuda.is_available())
print(torch.version.cuda)
# Install PyTorch with CUDA
pip install torch torchvision --index-url https://download.pytorch.org/whl/cu121
# If CUDA works but SAM doesn't use it
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
sam.to("cuda") # Explicitly move to GPU
```
### Import errors
**Error**: `ModuleNotFoundError: No module named 'segment_anything'`
**Solutions**:
```bash
# Install from GitHub
pip install git+https://github.com/facebookresearch/segment-anything.git
# Or clone and install
git clone https://github.com/facebookresearch/segment-anything.git
cd segment-anything
pip install -e .
# Verify installation
python -c "from segment_anything import sam_model_registry; print('OK')"
```
### Missing dependencies
**Error**: `ModuleNotFoundError: No module named 'cv2'` or similar
**Solutions**:
```bash
# Install all optional dependencies
pip install opencv-python pycocotools matplotlib onnxruntime onnx
# For pycocotools on Windows
pip install pycocotools-windows
```
## Model Loading Issues
### Checkpoint not found
**Error**: `FileNotFoundError: checkpoint file not found`
**Solutions**:
```bash
# Download correct checkpoint
wget https://dl.fbaipublicfiles.com/segment_anything/sam_vit_h_4b8939.pth
# Verify file integrity
md5sum sam_vit_h_4b8939.pth
# Expected: a7bf3b02f3ebf1267aba913ff637d9a2
# Use absolute path
sam = sam_model_registry["vit_h"](checkpoint="/full/path/to/sam_vit_h_4b8939.pth")
```
### Model type mismatch
**Error**: `KeyError: 'unexpected key in state_dict'`
**Solutions**:
```python
# Ensure model type matches checkpoint
# vit_h checkpoint → vit_h model
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
# vit_l checkpoint → vit_l model
sam = sam_model_registry["vit_l"](checkpoint="sam_vit_l_0b3195.pth")
# vit_b checkpoint → vit_b model
sam = sam_model_registry["vit_b"](checkpoint="sam_vit_b_01ec64.pth")
```
### Out of memory during load
**Error**: `CUDA out of memory` during model loading
**Solutions**:
```python
# Use smaller model
sam = sam_model_registry["vit_b"](checkpoint="sam_vit_b_01ec64.pth")
# Load to CPU first, then move
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
sam.to("cpu")
torch.cuda.empty_cache()
sam.to("cuda")
# Use half precision
sam = sam_model_registry["vit_h"](checkpoint="sam_vit_h_4b8939.pth")
sam = sam.half()
sam.to("cuda")
```
## Inference Issues
### Image format errors
**Error**: `ValueError: expected input to have 3 channels`
**Solutions**:
```python
import cv2
# Ensure RGB format
image = cv2.imread("image.jpg")
image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB) # BGR to RGB
# Convert grayscale to RGB
if len(image.shape) == 2:
image = cv2.cvtColor(image, cv2.COLOR_GRAY2RGB)
# Handle RGBA
if image.shape[2] == 4:
image = image[:, :, :3] # Drop alpha channel
```
### Coordinate errors
**Error**: `IndexError: index out of bounds` or incorrect mask location
**Solutions**:
```python
# Ensure points are (x, y) not (row, col)
# x = column index, y = row index
point = np.array([[x, y]]) # Correct
# Verify coordinates are within image bounds
h, w = image.shape[:2]
assert 0 <= x < w and 0 <= y < h, "Point outside image"
# For bounding boxes: [x1, y1, x2, y2]
box = np.array([x1, y1, x2, y2])
assert x1 < x2 and y1 < y2, "Invalid box coordinates"
```
### Empty or incorrect masks
**Problem**: Masks don't match expected object
**Solutions**:
```python
# Try multiple prompts
input_points = np.array([[x1, y1], [x2, y2]])
input_labels = np.array([1, 1]) # Multiple foreground points
# Add background points
input_points = np.array([[obj_x, obj_y], [bg_x, bg_y]])
input_labels = np.array([1, 0]) # 1=foreground, 0=background
# Use box prompt for large objects
box = np.array([x1, y1, x2, y2])
masks, scores, _ = predictor.predict(box=box, multimask_output=False)
# Combine box and point
masks, scores, _ = predictor.predict(
point_coords=np.array([[center_x, center_y]]),
point_labels=np.array([1]),
box=np.array([x1, y1, x2, y2]),
multimask_output=True
)
# Check scores and select best
print(f"Scores: {scores}")
best_mask = masks[np.argmax(scores)]
```
### Slow inference
**Problem**: Prediction takes too long
**Solutions**:
```python
# Use smaller model
sam = sam_model_registry["vit_b"](checkpoint="sam_vit_b_01ec64.pth")
# Reuse image embeddings
predictor.set_image(image) # Compute once
for point in points:
masks, _, _ = predictor.predict(...) # Fast, reuses embeddings
# Reduce automatic generation points
mask_generator = SamAutomaticMaskGenerator(
model=sam,
points_per_side=16, # Default is 32
)
# Use ONNX for deployment
# Export: python scripts/export_onnx_model.py --return-single-mask
```
## Automatic Mask Generation Issues
### Too many masks
**Problem**: Generating thousands of overlapping masks
**Solutions**:
```python
mask_generator = SamAutomaticMaskGenerator(
model=sam,
points_per_side=16, # Reduce from 32
pred_iou_thresh=0.92, # Increase from 0.88
stability_score_thresh=0.98, # Increase from 0.95
box_nms_thresh=0.5, # More aggressive NMS
min_mask_region_area=500, # Remove small masks
)
```
### Too few masks
**Problem**: Missing objects in automatic generation
**Solutions**:
```python
mask_generator = SamAutomaticMaskGenerator(
model=sam,
points_per_side=64, # Increase density
pred_iou_thresh=0.80, # Lower threshold
stability_score_thresh=0.85, # Lower threshold
crop_n_layers=2, # Add multi-scale
min_mask_region_area=0, # Keep all masks
)
```
### Small objects missed
**Problem**: Automatic generation misses small objects
**Solutions**:
```python
# Use crop layers for multi-scale detection
mask_generator = SamAutomaticMaskGenerator(
model=sam,
crop_n_layers=2,
crop_n_points_downscale_factor=1, # Don't reduce points in crops
min_mask_region_area=10, # Very small minimum
)
# Or process image patches
def segment_with_patches(image, patch_size=512, overlap=64):
h, w = image.shape[:2]
all_masks = []
for y in range(0, h, patch_size - overlap):
for x in range(0, w, patch_size - overlap):
patch = image[y:y+patch_size, x:x+patch_size]
masks = mask_generator.generate(patch)
# Offset masks to original coordinates
for m in masks:
m['bbox'][0] += x
m['bbox'][1] += y
# Offset segmentation mask too
all_masks.extend(masks)
return all_masks
```
## Memory Issues
### CUDA out of memory
**Error**: `torch.cuda.OutOfMemoryError: CUDA out of memory`
**Solutions**:
```python
# Use smaller model
sam = sam_model_registry["vit_b"](checkpoint="sam_vit_b_01ec64.pth")
# Clear cache between images
torch.cuda.empty_cache()
# Process images sequentially, not batched
for image in images:
predictor.set_image(image)
masks, _, _ = predictor.predict(...)
torch.cuda.empty_cache()
# Reduce image size
max_size = 1024
h, w = image.shape[:2]
if max(h, w) > max_size:
scale = max_size / max(h, w)
image = cv2.resize(image, (int(w*scale), int(h*scale)))
# Use CPU for large batch processing
sam.to("cpu")
```
### RAM out of memory
**Problem**: System runs out of RAM
**Solutions**:
```python
# Process images one at a time
for img_path in image_paths:
image = cv2.imread(img_path)
masks = process_image(image)
save_results(masks)
del image, masks
gc.collect()
# Use generators instead of lists
def generate_masks_lazy(image_paths):
for path in image_paths:
image = cv2.imread(path)
masks = mask_generator.generate(image)
yield path, masks
```
## ONNX Export Issues
### Export fails
**Error**: Various export errors
**Solutions**:
```bash
# Install correct ONNX version
pip install onnx==1.14.0 onnxruntime==1.15.0
# Use correct opset version
python scripts/export_onnx_model.py \
--checkpoint sam_vit_h_4b8939.pth \
--model-type vit_h \
--output sam.onnx \
--opset 17
```
### ONNX runtime errors
**Error**: `ONNXRuntimeError` during inference
**Solutions**:
```python
import onnxruntime
# Check available providers
print(onnxruntime.get_available_providers())
# Use CPU provider if GPU fails
session = onnxruntime.InferenceSession(
"sam.onnx",
providers=['CPUExecutionProvider']
)
# Verify input shapes
for input in session.get_inputs():
print(f"{input.name}: {input.shape}")
```
## HuggingFace Integration Issues
### Processor errors
**Error**: Issues with SamProcessor
**Solutions**:
```python
from transformers import SamModel, SamProcessor
# Use matching processor and model
model = SamModel.from_pretrained("facebook/sam-vit-huge")
processor = SamProcessor.from_pretrained("facebook/sam-vit-huge")
# Ensure input format
input_points = [[[x, y]]] # Nested list for batch dimension
inputs = processor(image, input_points=input_points, return_tensors="pt")
# Post-process correctly
masks = processor.image_processor.post_process_masks(
outputs.pred_masks.cpu(),
inputs["original_sizes"].cpu(),
inputs["reshaped_input_sizes"].cpu()
)
```
## Quality Issues
### Jagged mask edges
**Problem**: Masks have rough, pixelated edges
**Solutions**:
```python
import cv2
from scipy import ndimage
def smooth_mask(mask, sigma=2):
"""Smooth mask edges."""
# Gaussian blur
smooth = ndimage.gaussian_filter(mask.astype(float), sigma=sigma)
return smooth > 0.5
def refine_edges(mask, kernel_size=5):
"""Refine mask edges with morphological operations."""
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (kernel_size, kernel_size))
# Close small gaps
closed = cv2.morphologyEx(mask.astype(np.uint8), cv2.MORPH_CLOSE, kernel)
# Open to remove noise
opened = cv2.morphologyEx(closed, cv2.MORPH_OPEN, kernel)
return opened.astype(bool)
```
### Incomplete segmentation
**Problem**: Mask doesn't cover entire object
**Solutions**:
```python
# Add multiple points
input_points = np.array([
[obj_center_x, obj_center_y],
[obj_left_x, obj_center_y],
[obj_right_x, obj_center_y],
[obj_center_x, obj_top_y],
[obj_center_x, obj_bottom_y]
])
input_labels = np.array([1, 1, 1, 1, 1])
# Use bounding box
masks, _, _ = predictor.predict(
box=np.array([x1, y1, x2, y2]),
multimask_output=False
)
# Iterative refinement
mask_input = None
for point in points:
masks, scores, logits = predictor.predict(
point_coords=point.reshape(1, 2),
point_labels=np.array([1]),
mask_input=mask_input,
multimask_output=False
)
mask_input = logits
```
## Common Error Messages
| Error | Cause | Solution |
|-------|-------|----------|
| `CUDA out of memory` | GPU memory full | Use smaller model, clear cache |
| `expected 3 channels` | Wrong image format | Convert to RGB |
| `index out of bounds` | Invalid coordinates | Check point/box bounds |
| `checkpoint not found` | Wrong path | Use absolute path |
| `unexpected key` | Model/checkpoint mismatch | Match model type |
| `invalid box coordinates` | x1 > x2 or y1 > y2 | Fix box format |
## Getting Help
1. **GitHub Issues**: https://github.com/facebookresearch/segment-anything/issues
2. **HuggingFace Forums**: https://discuss.huggingface.co
3. **Paper**: https://arxiv.org/abs/2304.02643
### Reporting Issues
Include:
- Python version
- PyTorch version: `python -c "import torch; print(torch.__version__)"`
- CUDA version: `python -c "import torch; print(torch.version.cuda)"`
- SAM model type (vit_b/l/h)
- Full error traceback
- Minimal reproducible code