OpenIGTLink/ProtocolV2/Type/Image

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Summary

The IMAGE format supports 2D or 3D images with metric information including image matrix size, voxel size, coordinate system type, position, and orientation. The body section of the IMAGE data consists of two parts: image header to transfer the metric information and image body to transfer the array of pixel or voxel values. The data type of pixel or voxel can be either scalar or vector, and numerical values can be 8-, 16-, 32-bit integer, or 32- or 64-bit floating point. The pixel values can be either big-endian or little-endian, since the sender software can specify the byte order in the image header. The format also supports “partial image transfer”, in which a region of the image is transferred instead of the whole image. This mechanism is suitable for real-time applications, in which images are updated region-by-region. The sub-volume must be box-shaped and defined by 6 parameters consisting of the indices for the corner voxel of the sub-volume and matrix size of the sub-volume.

Message Types

IMAGE

Data	Type	Description
V	unsigned short	version number
T	8bit unsigned int	Number of Image Components (1:Scalar, >1:Vector). (NOTE: Vector data is stored fully interleaved.)
S	8bit unsigned int	Scalar type (2:int8 3:uint8 4:int16 5:uint16 6:int32 7:uint32 10:float32 11:float64)
E	8bit unsigned int	Endian for image data (1:BIG 2:LITTLE) (NOTE: values in image header is fixed to BIG endian)
O	8bit unsigned int	image coordinate (1:RAS 2:LPS)
RI, RJ, RK	16 bit unsigned int	Number of pixels in each direction
PX, PY, PZ	32 bit float	center position of the image
TX, TY, TZ	32 bit float	Transverse vector (direction for 'i' index) / The length represents pixel size in 'i' direction
SX, SY, SZ	32 bit float	Transverse vector (direction for 'j' index) / The length represents pixel size in 'j' direction
NX, NY, NZ	32 bit float	Normal vector of image plane(direction for 'k' index) / The length represents pixel size in 'z' direction or slice thickness
DI, DJ, DK	16 bit unsigned int	Starting index of subvolume
DRI, DRJ, DRK	16 bit unsigned int	number of pixels of subvolume
IMAGE_DATA	Binary image data ()	Image data (endian is determined by "E" field)

Notes

• The example application of vector type is:
  • Vector field
  • Image with complex pixel values (e.g. MRI raw data)
  • Color image
• Vector data is stored fully interleaved. For example, if you are storing RGB color image, the order should be: RGBRGBRGB...

Implementations

IMAGE type is implemented in the following files:

• igtlImageMessage.h
• igtlImageMessage.cxx

Contributors

This message type was originally proposed in version 1 protocol.