_vx_imagepatch_addressing_t Struct Reference

Data Fields

_vx_imagepatch_addressing_t Struct Reference

The addressing image patch structure is used by the Host only to address pixels in an image patch. The fields of the structure are defined as: More...

#include <docs-6.1.1/amd_openvx/openvx/include/VX/vx_types.h>

Data Fields
vx_uint32	dim_x
	Width of patch in X dimension in pixels.
vx_uint32	dim_y
	Height of patch in Y dimension in pixels.
vx_int32	stride_x
	Stride in X dimension in bytes.
vx_int32	stride_y
	Stride in Y dimension in bytes.
vx_uint32	scale_x
	Scale of X dimension. For sub-sampled planes this is the scaling factor of the dimension of the plane in relation to the zero plane. Use VX_SCALE_UNITY in the numerator.
vx_uint32	scale_y
	Scale of Y dimension. For sub-sampled planes this is the scaling factor of the dimension of the plane in relation to the zero plane. Use VX_SCALE_UNITY in the numerator.
vx_uint32	step_x
	Step of X dimension in pixels.
vx_uint16	step_y
	Step of Y dimension in pixels.
vx_uint16	stride_x_bits
	Stride in X dimension in bits. Used when stride_x is not an integer number of bytes.

Detailed Description

The addressing image patch structure is used by the Host only to address pixels in an image patch. The fields of the structure are defined as:

• dim - The dimensions of the image in logical pixel units in the x & y direction.
• stride - The physical byte distance from a logical pixel to the next logically adjacent pixel in the positive x or y direction.
• scale - The relationship of scaling from the primary plane (typically the zero indexed plane) to this plane. An integer down-scaling factor of \( f \) shall be set to a value equal to \( scale = \frac{unity}{f} \) and an integer up-scaling factor of \( f \) shall be set to a value of \( scale = unity * f \). \( unity \) is defined as VX_SCALE_UNITY.
• step - The step is the number of logical pixel units to skip to arrive at the next physically unique pixel. For example, on a plane that is half-scaled in a dimension, the step in that dimension is 2 to indicate that every other pixel in that dimension is an alias. This is useful in situations where iteration over unique pixels is required, such as in serializing or de-serializing the image patch information.

  See also

  vxMapImagePatch

  Note

  For VX_DF_IMAGE_U1 images it is defined that stride_x == 0 since it is less than one byte. The least significant bit (bit number 0, value 1) in the first byte in the image, is the left-most pixel in the upper left corner, i.e. origo. A VX_DF_IMAGE_U1 image always start on a byte boundary and each row has a stride_y that is a multiple of whole bytes, which means padding bits of undefined value may be present at the end of each row. Imagepatches can only be accessed at a multiple of eight pixels: the x-coordinate must be a multiple of eight. Individual pixel access is also different: the byte at the imagepatch-calculated pointer value is a collection of eight pixels. Each byte can then be masked with the bit-mask 1 << (x % 8) to get individual pixel values (shifted x times). See sub_image_access for an example.

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The documentation for this struct was generated from the following file:

• docs-6.1.1/amd_openvx/openvx/include/VX/vx_types.h