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Convert vehicle coordinates to image coordinates



imagePoints = vehicleToImage(monoCam,vehiclePoints) converts [x y] or [x y z] vehicle coordinates to [x y] image coordinates by applying a projective transformation. The monocular camera object, monoCam, contains the camera parameters.


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Create a forward-facing monocular camera sensor mounted on an ego vehicle. Examine an image captured from the camera and determine locations within the image in both vehicle and image coordinates.

Set the intrinsic parameters of the camera. Specify the focal length, the principal point of the image plane, and the output image size. Units are in pixels. Save the intrinsics as a cameraIntrinsics object.

focalLength = [800 800];
principalPoint = [320 240];
imageSize = [480 640];

intrinsics = cameraIntrinsics(focalLength,principalPoint,imageSize);

Specify the position of the camera. Position the camera 2.18 meters above the ground with a 14-degree pitch toward the ground.

height = 2.18;
pitch = 14;

Define a monocular camera sensor using the intrinsic camera parameters and the position of the camera. Load an image from the camera.

sensor = monoCamera(intrinsics,height,'Pitch',pitch);

Ioriginal = imread('road.png');
title('Original Image')

Determine the image coordinates of a point 10 meters directly in front of the camera. The X-axis points forward from the camera and the Y-axis points to the left.

xyVehicleLoc1 = [10 0];
xyImageLoc1 = vehicleToImage(sensor,xyVehicleLoc1)
xyImageLoc1 = 1×2

  320.0000  216.2296

Display the point on the image.

IvehicleToImage = insertMarker(Ioriginal,xyImageLoc1);
IvehicleToImage = insertText(IvehicleToImage,xyImageLoc1 + 5,'10 meters');
title('Vehicle-to-Image Point')

Determine the vehicle coordinates of a point that lies on the road surface in the image.

xyImageLoc2 = [300 300];
xyVehicleLoc2 = imageToVehicle(sensor,xyImageLoc2)
xyVehicleLoc2 = 1×2

    6.5959    0.1732

The point is about 6.6 meters in front of the vehicle and about 0.17 meters to the left of the vehicle center.

Display the vehicle coordinates of the point on the image.

IimageToVehicle = insertMarker(Ioriginal,xyImageLoc2);
displayText = sprintf('(%.2f m, %.2f m)',xyVehicleLoc2);
IimageToVehicle = insertText(IimageToVehicle,xyImageLoc2 + 5,displayText);

title('Image-to-Vehicle Point')

Input Arguments

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Monocular camera parameters, specified as a monoCamera object.

Vehicle points, specified as an M-by-2 or M-by-3 matrix containing M number of [x y] or [x y z] vehicle coordinates.

Output Arguments

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Image points, returned as an M-by-2 matrix containing M number of [x y] image coordinates.

More About

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Vehicle Coordinate System

In the vehicle coordinate system (XV, YV, ZV) defined by vehicleToImage:

  • The XV-axis points forward from the vehicle.

  • The YV-axis points to the left, as viewed when facing forward.

  • The ZV-axis points up from the ground to maintain the right-handed coordinate system.

The default origin of this coordinate system is on the road surface, directly below the camera center. The focal point of the camera defines this center point.

Vehicle with front-facing camera and Xv-axis, Yv-axis, and Zv-axis labeled

To change the placement of the origin within the vehicle coordinate system, update the SensorLocation property.

For more details about the vehicle coordinate system, see Coordinate Systems in Automated Driving Toolbox.

Angle Directions

The monocular camera sensor uses clockwise positive angle directions when looking in the positive direction of the Z-, Y-, and X-axes, respectively.

2-D and 3-D pitch, yaw, and roll camera views

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2017a