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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_linear_interp_q7.c
* Description: Q7 linear interpolation
*
* $Date: 23 April 2021
* $Revision: V1.9.0
*
* Target Processor: Cortex-M and Cortex-A cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "dsp/interpolation_functions.h"
/**
@ingroup groupInterpolation
*/
/**
* @addtogroup BilinearInterpolate
* @{
*/
/**
* @brief Q7 bilinear interpolation.
* @param[in,out] S points to an instance of the interpolation structure.
* @param[in] X interpolation coordinate in 12.20 format.
* @param[in] Y interpolation coordinate in 12.20 format.
* @return out interpolated value.
*/
q7_t arm_bilinear_interp_q7(
arm_bilinear_interp_instance_q7 * S,
q31_t X,
q31_t Y)
{
q63_t acc = 0; /* output */
q31_t out; /* Temporary output */
q31_t xfract, yfract; /* X, Y fractional parts */
q7_t x1, x2, y1, y2; /* Nearest output values */
int32_t rI, cI; /* Row and column indices */
q7_t *pYData = S->pData; /* pointer to output table values */
uint32_t nCols = S->numCols; /* num of rows */
/* Input is in 12.20 format */
/* 12 bits for the table index */
/* Index value calculation */
rI = ((X & (q31_t)0xFFF00000) >> 20);
/* Input is in 12.20 format */
/* 12 bits for the table index */
/* Index value calculation */
cI = ((Y & (q31_t)0xFFF00000) >> 20);
/* Care taken for table outside boundary */
/* Returns zero output when values are outside table boundary */
if (rI < 0 || rI > (S->numCols - 2) || cI < 0 || cI > (S->numRows - 2))
{
return (0);
}
/* 20 bits for the fractional part */
/* xfract should be in 12.20 format */
xfract = (X & (q31_t)0x000FFFFF);
/* Read two nearest output values from the index */
x1 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI) ];
x2 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI) + 1];
/* 20 bits for the fractional part */
/* yfract should be in 12.20 format */
yfract = (Y & (q31_t)0x000FFFFF);
/* Read two nearest output values from the index */
y1 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI + 1) ];
y2 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI + 1) + 1];
/* Calculation of x1 * (1-xfract ) * (1-yfract) and acc is in 16.47 format */
out = ((x1 * (0xFFFFF - xfract)));
acc = (((q63_t) out * (0xFFFFF - yfract)));
/* x2 * (xfract) * (1-yfract) in 2.22 and adding to acc */
out = ((x2 * (0xFFFFF - yfract)));
acc += (((q63_t) out * (xfract)));
/* y1 * (1 - xfract) * (yfract) in 2.22 and adding to acc */
out = ((y1 * (0xFFFFF - xfract)));
acc += (((q63_t) out * (yfract)));
/* y2 * (xfract) * (yfract) in 2.22 and adding to acc */
out = ((y2 * (yfract)));
acc += (((q63_t) out * (xfract)));
/* acc in 16.47 format and down shift by 40 to convert to 1.7 format */
return ((q7_t)(acc >> 40));
}
/**
* @} end of BilinearInterpolate group
*/
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