CompressedImage

(To be removed) Create compressed image message

CompressedImage object will be removed in a future release. Use message structure format when you create ROS messages using the rosmessage function, by specifying the Dataformat name-value argument as "struct". You can use rosReadImage and rosWriteImage functions to read and write compressed image data from ROS messages respectively. For more information, see ROS Message Structure Functions.

Description

The CompressedImage object is an implementation of the sensor_msgs/CompressedImage message type in ROS. The object contains the compressed image and meta-information about the message. You can create blank CompressedImage messages and populate them with data, or subscribe to image messages over the ROS network. To convert the image to a MATLAB^® image, use the readImage function.

Only images that are sent through the ROS Image Transport package are supported for conversion to MATLAB images.

Creation

Syntax

msg = rosmessage('sensor_msgs/CompressedImage')

Description

msg = rosmessage('sensor_msgs/CompressedImage') creates an empty CompressedImage object. To specify image data, use the msg.Data property. You can also get these image messages off the ROS network using rossubscriber.

Properties

MessageType — Message type of ROS message

Read-only: character vector

This property is read-only.

Message type of ROS message, returned as a character vector.

Data Types: char

Header — ROS Header message

Read-only: Header object

This property is read-only.

ROS Header message, returned as a Header object. This header message contains the MessageType, sequence (Seq), timestamp (Stamp), and FrameId.

Format — Image format

character vector

Image format, specified as a character vector.

Example: 'bgr8; jpeg compressed bgr8'

Data — Image data

uint8 array

Image data, specified as a uint8 array.

Object Functions

readImage

(To be removed) Convert ROS image data into MATLAB image

Examples

Read and Write CompressedImage Messages

Read and write a sample ROS CompressedImage message by converting it.

Load sample ROS messages and inspect the image message. The imgcomp object is a sample ROS CompressedImage message object.

exampleHelperROSLoadMessages
imgcomp

imgcomp = 
  ROS CompressedImage message with properties:

    MessageType: 'sensor_msgs/CompressedImage'
         Header: [1×1 Header]
         Format: 'bgr8; jpeg compressed bgr8'
           Data: [30376×1 uint8]

  Use showdetails to show the contents of the message

Create a MATLAB image from the CompressedImage message using readImage and display it.

I = readImage(imgcomp);
imshow(I)

Create Blank Compressed Image Message

compImg = rosmessage('sensor_msgs/CompressedImage')

compImg = 
  ROS CompressedImage message with properties:

    MessageType: 'sensor_msgs/CompressedImage'
         Header: [1×1 Header]
         Format: ''
           Data: [0×1 uint8]

  Use showdetails to show the contents of the message

Version History

Introduced in R2019b

R2021a: ROS Message Structure Functions

You can now create messages as structures with fields matching the message object properties. Using structures typically improves performance of creating, updating, and using ROS messages, but message fields are no longer validated when set. Message types and corresponding field values from the structures are validated when sent across the network.

To support message structures as inputs, new functions that operate on specialized ROS messages have been provided. These new functions are based on the existing object functions of message objects, but support ROS and ROS 2 message structures as inputs instead of message objects.

The object functions will be removed in a future release.

Message Types	Object Function Name	New Function Name
Image CompressedImage	readImage writeImage	rosReadImage rosWriteImage
LaserScan	readCartesian readScanAngles lidarScan plot	rosReadCartesian rosReadScanAngles rosReadLidarScan rosPlot
PointCloud2	apply readXYZ readRGB readAllFieldNames readField scatter3	rosApplyTransform rosReadXYZ rosReadRGB rosReadAllFieldNames rosReadField rosPlot
Quaternion	readQuaternion	rosReadQuaternion
OccupancyGrid	readBinaryOccupanyGrid readOccupancyGrid writeBinaryOccupanyGrid writeOccupanyGrid	rosReadOccupancyGrid rosReadBinaryOccupancyGrid rosReadOccupancyGrid rosWriteBinaryOccupancyGrid rosWriteOccupancyGrid
Octomap	readOccupancyMap3D	rosReadOccupancyMap3D
PointStamped PoseStamped QuaternionStamped Vector3Stamped TransformStamped	apply	rosApplyTransform
All messages	showdetails	rosShowDetails