Laplacian Image Pyramid

Detailed Description

Computes a Laplacian Image Pyramid from an input image.

This vision function creates the Laplacian image pyramid from the input image. First, a Gaussian pyramid is created with the scale attribute VX_SCALE_PYRAMID_HALF and the number of levels equal to \(N+1\), where \(N\) is the number of levels in the laplacian pyramid. The border mode for the Gaussian pyramid calculation should be VX_BORDER_REPLICATE. Then, for each \(i = 0..N-1\), the Laplacian level \(L_i\) is computed as:

\[ L_i = G_i - UpSample(G_{i+1}). \]

Here \(G_i\) is the \(i\)-th level of the Gaussian pyramid.

The \(UpSample(I)\) is computed by injecting even zero rows and columns and then convolves the result with the Gaussian 5x5 filter multiplied by 4.

\[ UpSample(I)_{x,y} = 4 \sum_{k=-2}^{2} \sum_{l=-2}^{2} I_{x-k,y-l}^{'} W_{k+2,l+2} \]

\[ I_{x,y}^{'} = \begin{cases} I_{\frac{x}{2},\frac{y}{2}} & \text{if x and y are even} \cr 0 & \text{otherwise} \end{cases} \]

\[ \mathbf{W}=\frac{1}{256} * \begin{vmatrix} 1 & 4 & 6 & 4 & 1 \\ 4 & 16 & 24 & 16 & 4 \\ 6 & 24 & 36 & 24 & 6 \\ 4 & 16 & 24 & 16 & 4 \\ 1 & 4 & 6 & 4 & 1 \\ \end{vmatrix} \]

\(L_0\) shall always have the same resolution as the input image. The output image is equal to \(G_N\).

The border mode for the UpSample calculation should be VX_BORDER_REPLICATE.

Functions
vx_node VX_API_CALL	vxLaplacianPyramidNode (vx_graph graph, vx_image input, vx_pyramid laplacian, vx_image output)
	[Graph] Creates a node for a Laplacian Image Pyramid. More...
vx_status VX_API_CALL	vxuLaplacianPyramid (vx_context context, vx_image input, vx_pyramid laplacian, vx_image output)
	[Immediate] Computes a Laplacian pyramid from an input image. More...

Function Documentation

vx_node VX_API_CALL vxLaplacianPyramidNode	(	vx_graph	graph,
		vx_image	input,
		vx_pyramid	laplacian,
		vx_image	output
	)

[Graph] Creates a node for a Laplacian Image Pyramid.

Parameters

[in]	graph	The reference to the graph.
[in]	input	The input image in VX_DF_IMAGE_U8 or VX_DF_IMAGE_S16 format.
[out]	laplacian	The Laplacian pyramid with VX_DF_IMAGE_S16 to construct.
[out]	output	The lowest resolution image in VX_DF_IMAGE_U8 or VX_DF_IMAGE_S16 format necessary to reconstruct the input image from the pyramid. The output image format should be same as input image format.

See also

Object: Pyramid

Returns

vx_node.

Return values

vx_node

A node reference. Any possible errors preventing a successful creation should be checked using vxGetStatus

vx_status VX_API_CALL vxuLaplacianPyramid	(	vx_context	context,
		vx_image	input,
		vx_pyramid	laplacian,
		vx_image	output
	)

[Immediate] Computes a Laplacian pyramid from an input image.

Parameters

[in]	context	The reference to the overall context.
[in]	input	The input image in VX_DF_IMAGE_U8 or VX_DF_IMAGE_S16 format.
[out]	laplacian	The Laplacian pyramid with VX_DF_IMAGE_S16 to construct.
[out]	output	The lowest resolution image in VX_DF_IMAGE_U8 or VX_DF_IMAGE_S16 format necessary to reconstruct the input image from the pyramid. The output image format should be same as input image format.

See also

Object: Pyramid

Returns

A vx_status enumeration.

Return values

VX_SUCCESS	Success.
*	An error occured. See vx_status_e