Instance Segmentation Example

Content:

PyTorch Version with Trainer
Reload and Perform Inference
Note on Custom Data

PyTorch Version with Trainer

This model is based on the script run_instance_segmentation.py. The script uses the 🤗 Trainer API to manage training automatically, including distributed environments. Here, we fine-tune a Mask2Former model on a subsample of the ADE20K dataset. We created a small dataset with approximately 2,000 images containing only "person" and "car" annotations; all other pixels are marked as "background."

Here is the label2id mapping for this model:

label2id = {
    "person": 0,
    "car": 1,
}

The training was done with the following command:

python run_instance_segmentation.py \
    --model_name_or_path facebook/mask2former-swin-tiny-coco-instance \
    --output_dir finetune-instance-segmentation-ade20k-mini-mask2former \
    --dataset_name qubvel-hf/ade20k-mini \
    --do_reduce_labels \
    --image_height 256 \
    --image_width 256 \
    --do_train \
    --fp16 \
    --num_train_epochs 40 \
    --learning_rate 1e-5 \
    --lr_scheduler_type constant \
    --per_device_train_batch_size 8 \
    --gradient_accumulation_steps 2 \
    --dataloader_num_workers 8 \
    --dataloader_persistent_workers \
    --dataloader_prefetch_factor 4 \
    --do_eval \
    --evaluation_strategy epoch \
    --logging_strategy epoch \
    --save_strategy epoch \
    --save_total_limit 2 \
    --push_to_hub

Reload and Perform Inference

You can easily load this trained model and perform inference as follows:

import torch
import requests
import matplotlib.pyplot as plt

from PIL import Image
from transformers import Mask2FormerForUniversalSegmentation, Mask2FormerImageProcessor

# Load image
image = Image.open(requests.get("http://farm4.staticflickr.com/3017/3071497290_31f0393363_z.jpg", stream=True).raw)

# Load model and image processor
device = "cuda"
checkpoint = "qubvel-hf/finetune-instance-segmentation-ade20k-mini-mask2former"

model = Mask2FormerForUniversalSegmentation.from_pretrained(checkpoint, device_map=device)
image_processor = Mask2FormerImageProcessor.from_pretrained(checkpoint)

# Run inference on image
inputs = image_processor(images=[image], return_tensors="pt").to(device)
with torch.no_grad():
    outputs = model(**inputs)

# Post-process outputs
outputs = image_processor.post_process_instance_segmentation(outputs, target_sizes=[image.size[::-1]])

print("Mask shape: ", outputs[0]["segmentation"].shape)
print("Mask values: ", outputs[0]["segmentation"].unique())
for segment in outputs[0]["segments_info"]:
    print("Segment: ", segment)

Mask shape:  torch.Size([427, 640])
Mask values:  tensor([-1.,  0.,  1.,  2.,  3.,  4.,  5.,  6.])
Segment:  {'id': 0, 'label_id': 0, 'was_fused': False, 'score': 0.946127}
Segment:  {'id': 1, 'label_id': 1, 'was_fused': False, 'score': 0.961582}
Segment:  {'id': 2, 'label_id': 1, 'was_fused': False, 'score': 0.968367}
Segment:  {'id': 3, 'label_id': 1, 'was_fused': False, 'score': 0.819527}
Segment:  {'id': 4, 'label_id': 1, 'was_fused': False, 'score': 0.655761}
Segment:  {'id': 5, 'label_id': 1, 'was_fused': False, 'score': 0.531299}
Segment:  {'id': 6, 'label_id': 1, 'was_fused': False, 'score': 0.929477}

Use the following code to visualize the results:

import numpy as np
import matplotlib.pyplot as plt

segmentation = outputs[0]["segmentation"].numpy()

plt.figure(figsize=(10, 10))
plt.subplot(1, 2, 1)
plt.imshow(np.array(image))
plt.axis("off")
plt.subplot(1, 2, 2)
plt.imshow(segmentation)
plt.axis("off")
plt.show()