Basler Vision Connector Messaging: Image Format#

To standardize image transfer between camera streaming applications and image-driven applications, use the following format for transferring images. The ZeroMQ message consists of a multipart message with each frame/part described below.

This message format is prepared to support the streaming of multiple cameras.

The following image format namespaces are supported via this communication channel:

Message Envelope for ZeroMQ Messages on the Pub/Sub Channel#

Frame	Field	Description	Type
1	topic	Device identification	Binary string (UTF-8) to identify the device in the following syntax: device/{DeviceID}/stream
2	metadata	Metadata	Binary metadata JSON (UTF-8)
3	image	Image 1	Binary
4 … n	image	Image n - For multi-stream camera	Binary

Metadata JSON#

Field	Optional	Type	Default	Description
version	No	String	1	Metadata format version
count	No	Integer (32-bit unsigned)	1	Number of images in the message
timestamp	No	String	-	Date and time string UTF-8 ISO8601. Application host datetime
detail	No	Image Detail Object Array	-	Images details

Image Detail Object#

Field	Optional	Type	Default	Description
FormatNamespace	Yes	String	GenICam	Image format namespace. For GenICam pixel format, use `GenICam` and use `Compressed` for compressed formats.^a
Format	No	String	–	Image format^a
Width	No / Yes (encoded formats)	Integer	–	Image width
Height	No / Yes (encoded formats)	Integer	–	Image height
LinePadding	Yes	Integer	0	Number of bytes added at the end of the byte stream to reach a multiple of 4 bytes. For example, an image with 61 pixels, mono8, will have a line padding of 3, filling the stream to reach 64 bytes.
ImageData	No / Yes (for MQTT)	String	–	URI with the image data or a reference to the image data.^b This field is mandatory for ZeroMQ and isn't available for MQTT.

The following image format namespaces are supported via this communication channel:
- To send uncompressed images: namespace GenICam. Use The pixel format names from the GenICam pixel format naming convention as described in GenICam_PFNC_2_4.pdf in the format field.
- To send compressed images: namespace Compressed. The only supported value for compressed image formats in the format field is JPEG.
A proprietary message part URI with MIME-Type is used here. It references raw data in another message part.
Syntax: msgpart:{Message-Part-Index};{MIME-Type}
Examples:
- For GenICam image data: msgpart:2;application/octet-stream
- For

JSON entry carrying an error:#

Field	Optional	Type	Default	Description
Error	No	String	–	An error description with the reason for the error

Metadata Examples#

{
  "Type": "Image",
  "Data": {
    "FormatNamespace": "Compressed",
    "Format": "JPEG",
    "Width": 80,
    "Height": 60,
    "ImageData": "msgpart:2;image/jpeg"
  }
}

{
  "Type": "Image",
  "Data": {
    "FormatNamespace": "GenICam",
    "Format": "Mono8",
    "Width": 640,
    "Height": 480,
    "LinePadding": 0,
    "ImageData": "msgpart:3;application/octet-stream"
  }
}

{
  "Type": "Image",
  "Data": {
    "Error": "Some error message."
  }
}