Model Prediction with Ultralytics YOLO

Introduction

In the world of machine learning and computer vision, the process of making sense out of visual data is called 'inference' or 'prediction'. Ultralytics YOLO11 offers a powerful feature known as predict mode that is tailored for high-performance, real-time inference on a wide range of data sources.

Watch: How to Extract the Outputs from Ultralytics YOLO Model for Custom Projects.

Real-world Applications

Manufacturing	Sports	Safety
Vehicle Spare Parts Detection	Football Player Detection	People Fall Detection

Why Use Ultralytics YOLO for Inference?

Here's why you should consider YOLO11's predict mode for your various inference needs:

• Versatility: Capable of making inferences on images, videos, and even live streams.
• Performance: Engineered for real-time, high-speed processing without sacrificing accuracy.
• Ease of Use: Intuitive Python and CLI interfaces for rapid deployment and testing.
• Highly Customizable: Various settings and parameters to tune the model's inference behavior according to your specific requirements.

Key Features of Predict Mode

YOLO11's predict mode is designed to be robust and versatile, featuring:

• Multiple Data Source Compatibility: Whether your data is in the form of individual images, a collection of images, video files, or real-time video streams, predict mode has you covered.
• Streaming Mode: Use the streaming feature to generate a memory-efficient generator of Results objects. Enable this by setting stream=True in the predictor's call method.
• Batch Processing: The ability to process multiple images or video frames in a single batch, further speeding up inference time.
• Integration Friendly: Easily integrate with existing data pipelines and other software components, thanks to its flexible API.

Ultralytics YOLO models return either a Python list of Results objects, or a memory-efficient Python generator of Results objects when stream=True is passed to the model during inference:

from ultralytics import YOLO

# Load a model
model = YOLO("yolo11n.pt")  # pretrained YOLO11n model

# Run batched inference on a list of images
results = model(["image1.jpg", "image2.jpg"])  # return a list of Results objects

# Process results list
for result in results:
    boxes = result.boxes  # Boxes object for bounding box outputs
    masks = result.masks  # Masks object for segmentation masks outputs
    keypoints = result.keypoints  # Keypoints object for pose outputs
    probs = result.probs  # Probs object for classification outputs
    obb = result.obb  # Oriented boxes object for OBB outputs
    result.show()  # display to screen
    result.save(filename="result.jpg")  # save to disk

from ultralytics import YOLO

# Load a model
model = YOLO("yolo11n.pt")  # pretrained YOLO11n model

# Run batched inference on a list of images
results = model(["image1.jpg", "image2.jpg"], stream=True)  # return a generator of Results objects

# Process results generator
for result in results:
    boxes = result.boxes  # Boxes object for bounding box outputs
    masks = result.masks  # Masks object for segmentation masks outputs
    keypoints = result.keypoints  # Keypoints object for pose outputs
    probs = result.probs  # Probs object for classification outputs
    obb = result.obb  # Oriented boxes object for OBB outputs
    result.show()  # display to screen
    result.save(filename="result.jpg")  # save to disk

Inference Sources

YOLO11 can process different types of input sources for inference, as shown in the table below. The sources include static images, video streams, and various data formats. The table also indicates whether each source can be used in streaming mode with the argument stream=True ✅. Streaming mode is beneficial for processing videos or live streams as it creates a generator of results instead of loading all frames into memory.

Below are code examples for using each source type:

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define path to the image file
source = "path/to/image.jpg"

# Run inference on the source
results = model(source)  # list of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define current screenshot as source
source = "screen"

# Run inference on the source
results = model(source)  # list of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define remote image or video URL
source = "https://ultralytics.com/images/bus.jpg"

# Run inference on the source
results = model(source)  # list of Results objects

from PIL import Image

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Open an image using PIL
source = Image.open("path/to/image.jpg")

# Run inference on the source
results = model(source)  # list of Results objects

import cv2

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Read an image using OpenCV
source = cv2.imread("path/to/image.jpg")

# Run inference on the source
results = model(source)  # list of Results objects

import numpy as np

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Create a random numpy array of HWC shape (640, 640, 3) with values in range [0, 255] and type uint8
source = np.random.randint(low=0, high=255, size=(640, 640, 3), dtype="uint8")

# Run inference on the source
results = model(source)  # list of Results objects

import torch

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Create a random torch tensor of BCHW shape (1, 3, 640, 640) with values in range [0, 1] and type float32
source = torch.rand(1, 3, 640, 640, dtype=torch.float32)

# Run inference on the source
results = model(source)  # list of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define a path to a CSV file with images, URLs, videos and directories
source = "path/to/file.csv"

# Run inference on the source
results = model(source)  # list of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define path to video file
source = "path/to/video.mp4"

# Run inference on the source
results = model(source, stream=True)  # generator of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define path to directory containing images and videos for inference
source = "path/to/dir"

# Run inference on the source
results = model(source, stream=True)  # generator of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define a glob search for all JPG files in a directory
source = "path/to/dir/*.jpg"

# OR define a recursive glob search for all JPG files including subdirectories
source = "path/to/dir/**/*.jpg"

# Run inference on the source
results = model(source, stream=True)  # generator of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Define source as YouTube video URL
source = "https://youtu.be/LNwODJXcvt4"

# Run inference on the source
results = model(source, stream=True)  # generator of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Single stream with batch-size 1 inference
source = "rtsp://example.com/media.mp4"  # RTSP, RTMP, TCP, or IP streaming address

# Run inference on the source
results = model(source, stream=True)  # generator of Results objects

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Multiple streams with batched inference (e.g., batch-size 8 for 8 streams)
source = "path/to/list.streams"  # *.streams text file with one streaming address per line

# Run inference on the source
results = model(source, stream=True)  # generator of Results objects

rtsp://example.com/media1.mp4
rtsp://example.com/media2.mp4
rtmp://example2.com/live
tcp://192.168.1.100:554
...

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Run inference on the source
results = model(source=0, stream=True)  # generator of Results objects

Inference Arguments

model.predict() accepts multiple arguments that can be passed at inference time to override defaults:

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Run inference on 'bus.jpg' with arguments
model.predict("bus.jpg", save=True, imgsz=320, conf=0.5)

Inference arguments:

Visualization arguments:

Image and Video Formats

YOLO11 supports various image and video formats, as specified in ultralytics/data/utils.py. See the tables below for the valid suffixes and example predict commands.

Images

The below table contains valid Ultralytics image formats.

Videos

The below table contains valid Ultralytics video formats.

Working with Results

All Ultralytics predict() calls will return a list of Results objects:

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Run inference on an image
results = model("bus.jpg")  # list of 1 Results object
results = model(["bus.jpg", "zidane.jpg"])  # list of 2 Results objects

Results objects have the following attributes:

Results objects have the following methods:

For more details see the Results class documentation.

Boxes

Boxes object can be used to index, manipulate, and convert bounding boxes to different formats.

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Run inference on an image
results = model("bus.jpg")  # results list

# View results
for r in results:
    print(r.boxes)  # print the Boxes object containing the detection bounding boxes

Here is a table for the Boxes class methods and properties, including their name, type, and description:

For more details see the Boxes class documentation.

Masks

Masks object can be used index, manipulate and convert masks to segments.

from ultralytics import YOLO

# Load a pretrained YOLO11n-seg Segment model
model = YOLO("yolo11n-seg.pt")

# Run inference on an image
results = model("bus.jpg")  # results list

# View results
for r in results:
    print(r.masks)  # print the Masks object containing the detected instance masks

Here is a table for the Masks class methods and properties, including their name, type, and description:

For more details see the Masks class documentation.

Keypoints

Keypoints object can be used index, manipulate and normalize coordinates.

from ultralytics import YOLO

# Load a pretrained YOLO11n-pose Pose model
model = YOLO("yolo11n-pose.pt")

# Run inference on an image
results = model("bus.jpg")  # results list

# View results
for r in results:
    print(r.keypoints)  # print the Keypoints object containing the detected keypoints

Here is a table for the Keypoints class methods and properties, including their name, type, and description:

For more details see the Keypoints class documentation.

Probs

Probs object can be used index, get top1 and top5 indices and scores of classification.

from ultralytics import YOLO

# Load a pretrained YOLO11n-cls Classify model
model = YOLO("yolo11n-cls.pt")

# Run inference on an image
results = model("bus.jpg")  # results list

# View results
for r in results:
    print(r.probs)  # print the Probs object containing the detected class probabilities

Here's a table summarizing the methods and properties for the Probs class:

For more details see the Probs class documentation.

OBB

OBB object can be used to index, manipulate, and convert oriented bounding boxes to different formats.

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n-obb.pt")

# Run inference on an image
results = model("boats.jpg")  # results list

# View results
for r in results:
    print(r.obb)  # print the OBB object containing the oriented detection bounding boxes

Here is a table for the OBB class methods and properties, including their name, type, and description:

For more details see the OBB class documentation.

Plotting Results

The plot() method in Results objects facilitates visualization of predictions by overlaying detected objects (such as bounding boxes, masks, keypoints, and probabilities) onto the original image. This method returns the annotated image as a NumPy array, allowing for easy display or saving.

from PIL import Image

from ultralytics import YOLO

# Load a pretrained YOLO11n model
model = YOLO("yolo11n.pt")

# Run inference on 'bus.jpg'
results = model(["bus.jpg", "zidane.jpg"])  # results list

# Visualize the results
for i, r in enumerate(results):
    # Plot results image
    im_bgr = r.plot()  # BGR-order numpy array
    im_rgb = Image.fromarray(im_bgr[..., ::-1])  # RGB-order PIL image

    # Show results to screen (in supported environments)
    r.show()

    # Save results to disk
    r.save(filename=f"results{i}.jpg")

plot() Method Parameters

The plot() method supports various arguments to customize the output:

Thread-Safe Inference

Ensuring thread safety during inference is crucial when you are running multiple YOLO models in parallel across different threads. Thread-safe inference guarantees that each thread's predictions are isolated and do not interfere with one another, avoiding race conditions and ensuring consistent and reliable outputs.

When using YOLO models in a multi-threaded application, it's important to instantiate separate model objects for each thread or employ thread-local storage to prevent conflicts:

from threading import Thread

from ultralytics import YOLO


def thread_safe_predict(model, image_path):
    """Performs thread-safe prediction on an image using a locally instantiated YOLO model."""
    model = YOLO(model)
    results = model.predict(image_path)
    # Process results


# Starting threads that each have their own model instance
Thread(target=thread_safe_predict, args=("yolo11n.pt", "image1.jpg")).start()
Thread(target=thread_safe_predict, args=("yolo11n.pt", "image2.jpg")).start()

For an in-depth look at thread-safe inference with YOLO models and step-by-step instructions, please refer to our YOLO Thread-Safe Inference Guide. This guide will provide you with all the necessary information to avoid common pitfalls and ensure that your multi-threaded inference runs smoothly.

Streaming Source for-loop

Here's a Python script using OpenCV (cv2) and YOLO to run inference on video frames. This script assumes you have already installed the necessary packages (opencv-python and ultralytics).

import cv2

from ultralytics import YOLO

# Load the YOLO model
model = YOLO("yolo11n.pt")

# Open the video file
video_path = "path/to/your/video/file.mp4"
cap = cv2.VideoCapture(video_path)

# Loop through the video frames
while cap.isOpened():
    # Read a frame from the video
    success, frame = cap.read()

    if success:
        # Run YOLO inference on the frame
        results = model(frame)

        # Visualize the results on the frame
        annotated_frame = results[0].plot()

        # Display the annotated frame
        cv2.imshow("YOLO Inference", annotated_frame)

        # Break the loop if 'q' is pressed
        if cv2.waitKey(1) & 0xFF == ord("q"):
            break
    else:
        # Break the loop if the end of the video is reached
        break

# Release the video capture object and close the display window
cap.release()
cv2.destroyAllWindows()

This script will run predictions on each frame of the video, visualize the results, and display them in a window. The loop can be exited by pressing 'q'.

FAQ

What is Ultralytics YOLO and its predict mode for real-time inference?

Ultralytics YOLO is a state-of-the-art model for real-time object detection, segmentation, and classification. Its predict mode allows users to perform high-speed inference on various data sources such as images, videos, and live streams. Designed for performance and versatility, it also offers batch processing and streaming modes. For more details on its features, check out the Ultralytics YOLO predict mode.

How can I run inference using Ultralytics YOLO on different data sources?

Ultralytics YOLO can process a wide range of data sources, including individual images, videos, directories, URLs, and streams. You can specify the data source in the model.predict() call. For example, use 'image.jpg' for a local image or 'https://ultralytics.com/images/bus.jpg' for a URL. Check out the detailed examples for various inference sources in the documentation.

How do I optimize YOLO inference speed and memory usage?

To optimize inference speed and manage memory efficiently, you can use the streaming mode by setting stream=True in the predictor's call method. The streaming mode generates a memory-efficient generator of Results objects instead of loading all frames into memory. For processing long videos or large datasets, streaming mode is particularly useful. Learn more about streaming mode.

What inference arguments does Ultralytics YOLO support?

The model.predict() method in YOLO supports various arguments such as conf, iou, imgsz, device, and more. These arguments allow you to customize the inference process, setting parameters like confidence thresholds, image size, and the device used for computation. Detailed descriptions of these arguments can be found in the inference arguments section.

How can I visualize and save the results of YOLO predictions?

After running inference with YOLO, the Results objects contain methods for displaying and saving annotated images. You can use methods like result.show() and result.save(filename="result.jpg") to visualize and save the results. For a comprehensive list of these methods, refer to the working with results section.

📅 Created 1 year ago ✏️ Updated 27 days ago

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