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120 lines
4.0 KiB
C
120 lines
4.0 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_linear_interp_q31.c
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* Description: Q31 linear interpolation
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*
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* $Date: 23 April 2021
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* $Revision: V1.9.0
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*
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* Target Processor: Cortex-M and Cortex-A cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "dsp/interpolation_functions.h"
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/**
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@ingroup groupInterpolation
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*/
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/**
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* @addtogroup BilinearInterpolate
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* @{
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*/
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/**
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* @brief Q31 bilinear interpolation.
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* @param[in,out] S points to an instance of the interpolation structure.
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* @param[in] X interpolation coordinate in 12.20 format.
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* @param[in] Y interpolation coordinate in 12.20 format.
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* @return out interpolated value.
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*/
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q31_t arm_bilinear_interp_q31(
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arm_bilinear_interp_instance_q31 * S,
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q31_t X,
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q31_t Y)
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{
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q31_t out; /* Temporary output */
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q31_t acc = 0; /* output */
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q31_t xfract, yfract; /* X, Y fractional parts */
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q31_t x1, x2, y1, y2; /* Nearest output values */
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int32_t rI, cI; /* Row and column indices */
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q31_t *pYData = S->pData; /* pointer to output table values */
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uint32_t nCols = S->numCols; /* num of rows */
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/* Input is in 12.20 format */
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/* 12 bits for the table index */
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/* Index value calculation */
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rI = ((X & (q31_t)0xFFF00000) >> 20);
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/* Input is in 12.20 format */
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/* 12 bits for the table index */
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/* Index value calculation */
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cI = ((Y & (q31_t)0xFFF00000) >> 20);
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/* Care taken for table outside boundary */
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/* Returns zero output when values are outside table boundary */
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if (rI < 0 || rI > (S->numCols - 2) || cI < 0 || cI > (S->numRows - 2))
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{
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return (0);
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}
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/* 20 bits for the fractional part */
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/* shift left xfract by 11 to keep 1.31 format */
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xfract = (X & 0x000FFFFF) << 11U;
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/* Read two nearest output values from the index */
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x1 = pYData[(rI) + (int32_t)nCols * (cI) ];
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x2 = pYData[(rI) + (int32_t)nCols * (cI) + 1];
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/* 20 bits for the fractional part */
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/* shift left yfract by 11 to keep 1.31 format */
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yfract = (Y & 0x000FFFFF) << 11U;
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/* Read two nearest output values from the index */
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y1 = pYData[(rI) + (int32_t)nCols * (cI + 1) ];
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y2 = pYData[(rI) + (int32_t)nCols * (cI + 1) + 1];
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/* Calculation of x1 * (1-xfract ) * (1-yfract) and acc is in 3.29(q29) format */
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out = ((q31_t) (((q63_t) x1 * (0x7FFFFFFF - xfract)) >> 32));
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acc = ((q31_t) (((q63_t) out * (0x7FFFFFFF - yfract)) >> 32));
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/* x2 * (xfract) * (1-yfract) in 3.29(q29) and adding to acc */
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out = ((q31_t) ((q63_t) x2 * (0x7FFFFFFF - yfract) >> 32));
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acc += ((q31_t) ((q63_t) out * (xfract) >> 32));
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/* y1 * (1 - xfract) * (yfract) in 3.29(q29) and adding to acc */
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out = ((q31_t) ((q63_t) y1 * (0x7FFFFFFF - xfract) >> 32));
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acc += ((q31_t) ((q63_t) out * (yfract) >> 32));
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/* y2 * (xfract) * (yfract) in 3.29(q29) and adding to acc */
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out = ((q31_t) ((q63_t) y2 * (xfract) >> 32));
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acc += ((q31_t) ((q63_t) out * (yfract) >> 32));
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/* Convert acc to 1.31(q31) format */
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return ((q31_t)(acc << 2));
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}
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/**
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* @} end of BilinearInterpolate group
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*/
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