chapters/image.adoc

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=== Image Operators

==== RESIZE

Resizes a tensor. Resize is only allowed in the H and W dimensions.


The height dimension is scaled by factor (scale_y_n/scale_y_d).
The width dimension is scaled by factor (scale_x_n/scale_x_d).

The NEAREST_NEIGHBOR mode returns the value of the input tensor closest to the
calculated sample position for both floating-point and integer data formats.

Floating-point BILINEAR mode returns a bilinearly interpolated output value
based on the four closest input sample positions.

For integer BILINEAR interpolation mode, the output value must
be scaled by 1/(scale_y_n * scale_x_n) in a following operation to
complete the interpolation (for example with a RESCALE operator).

The following examples show practical uses of the parameters:

* For approximate uniform input sampling between (0, 0) and (IH - 1, IW - 1) set
** scale_y_n/scale_y_d = (OH - 1)/(IH - 1) as integer ratios
** scale_x_n/scale_x_d = (OW - 1)/(IW - 1) as integer ratios
** offset_x = 0, offset_y = 0, border_x = 0, border_y = 0

* For power of two upscale [OH - 1,OW - 1] = (1 << k) * [IH - 1, IW - 1],
sampling between (0,0) and (IH - 1,IW - 1), set:
** scale_y_n = (1 << k), scale_y_d = 1, offset_y = 0, border_y = 0
** scale_x_n = (1 << k), scale_x_d = 1, offset_x = 0, border_x = 0

* For power of two upscale [OH,OW] = (1 << k) * [IH,IW],
sampling range approximately (-0.5, -0.5) to (IH - 0.5, IW - 0.5), set:
** scale_y_n = 2 << k, scale_y_d = 2, offset_y = -(1 << k) + 1, border_y = (1 << k) - 1
** scale_x_n = 2 << k, scale_x_d = 2, offset_x = -(1 << k) + 1, border_x = (1 << k) - 1

The output dimensions can be derived from the input dimensions by inverting
the scale as described in the pseudocode. The [border_y, border_x] values
adjust the output size to allow fractional sampling beyond integer
input position (IH - 1,IW - 1).

include::{generated}/operators/RESIZE.adoc[]

*Resize Modes:*
|===
|Mode|Description

|NEAREST|Nearest Neighbor
|BILINEAR|Bilinear interpoloation
|===

[source,c++]
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include::{pseudocode}/operators/RESIZE.tosac[lines=10..-1]
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