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Diffstat (limited to 'Drivers/CMSIS/DSP/Source/InterpolationFunctions/arm_bilinear_interp_f32.c')
| -rw-r--r-- | Drivers/CMSIS/DSP/Source/InterpolationFunctions/arm_bilinear_interp_f32.c | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/Drivers/CMSIS/DSP/Source/InterpolationFunctions/arm_bilinear_interp_f32.c b/Drivers/CMSIS/DSP/Source/InterpolationFunctions/arm_bilinear_interp_f32.c new file mode 100644 index 0000000..fc001d7 --- /dev/null +++ b/Drivers/CMSIS/DSP/Source/InterpolationFunctions/arm_bilinear_interp_f32.c @@ -0,0 +1,161 @@ +/* ---------------------------------------------------------------------- + * Project: CMSIS DSP Library + * Title: arm_bilinear_interp_f32.c + * Description: Floating-point bilinear 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 + */ + +/** + * @defgroup BilinearInterpolate Bilinear Interpolation + * + * Bilinear interpolation is an extension of linear interpolation applied to a two dimensional grid. + * The underlying function <code>f(x, y)</code> is sampled on a regular grid and the interpolation process + * determines values between the grid points. + * Bilinear interpolation is equivalent to two step linear interpolation, first in the x-dimension and then in the y-dimension. + * Bilinear interpolation is often used in image processing to rescale images. + * The CMSIS DSP library provides bilinear interpolation functions for Q7, Q15, Q31, and floating-point data types. + * + * <b>Algorithm</b> + * \par + * The instance structure used by the bilinear interpolation functions describes a two dimensional data table. + * For floating-point, the instance structure is defined as: + * <pre> + * typedef struct + * { + * uint16_t numRows; + * uint16_t numCols; + * float32_t *pData; + * } arm_bilinear_interp_instance_f32; + * </pre> + * + * \par + * where <code>numRows</code> specifies the number of rows in the table; + * <code>numCols</code> specifies the number of columns in the table; + * and <code>pData</code> points to an array of size <code>numRows*numCols</code> values. + * The data table <code>pTable</code> is organized in row order and the supplied data values fall on integer indexes. + * That is, table element (x,y) is located at <code>pTable[x + y*numCols]</code> where x and y are integers. + * + * \par + * Let <code>(x, y)</code> specify the desired interpolation point. Then define: + * <pre> + * XF = floor(x) + * YF = floor(y) + * </pre> + * \par + * The interpolated output point is computed as: + * <pre> + * f(x, y) = f(XF, YF) * (1-(x-XF)) * (1-(y-YF)) + * + f(XF+1, YF) * (x-XF)*(1-(y-YF)) + * + f(XF, YF+1) * (1-(x-XF))*(y-YF) + * + f(XF+1, YF+1) * (x-XF)*(y-YF) + * </pre> + * Note that the coordinates (x, y) contain integer and fractional components. + * The integer components specify which portion of the table to use while the + * fractional components control the interpolation processor. + * + * \par + * if (x,y) are outside of the table boundary, Bilinear interpolation returns zero output. + */ + + + /** + * @addtogroup BilinearInterpolate + * @{ + */ + + + /** + * @brief Floating-point bilinear interpolation. + * @param[in,out] S points to an instance of the interpolation structure. + * @param[in] X interpolation coordinate. + * @param[in] Y interpolation coordinate. + * @return out interpolated value. + */ + float32_t arm_bilinear_interp_f32( + const arm_bilinear_interp_instance_f32 * S, + float32_t X, + float32_t Y) + { + float32_t out; + float32_t f00, f01, f10, f11; + float32_t *pData = S->pData; + int32_t xIndex, yIndex, index; + float32_t xdiff, ydiff; + float32_t b1, b2, b3, b4; + + xIndex = (int32_t) X; + yIndex = (int32_t) Y; + + /* Care taken for table outside boundary */ + /* Returns zero output when values are outside table boundary */ + if (xIndex < 0 || xIndex > (S->numCols - 2) || yIndex < 0 || yIndex > (S->numRows - 2)) + { + return (0); + } + + /* Calculation of index for two nearest points in X-direction */ + index = (xIndex ) + (yIndex ) * S->numCols; + + + /* Read two nearest points in X-direction */ + f00 = pData[index]; + f01 = pData[index + 1]; + + /* Calculation of index for two nearest points in Y-direction */ + index = (xIndex ) + (yIndex+1) * S->numCols; + + + /* Read two nearest points in Y-direction */ + f10 = pData[index]; + f11 = pData[index + 1]; + + /* Calculation of intermediate values */ + b1 = f00; + b2 = f01 - f00; + b3 = f10 - f00; + b4 = f00 - f01 - f10 + f11; + + /* Calculation of fractional part in X */ + xdiff = X - xIndex; + + /* Calculation of fractional part in Y */ + ydiff = Y - yIndex; + + /* Calculation of bi-linear interpolated output */ + out = b1 + b2 * xdiff + b3 * ydiff + b4 * xdiff * ydiff; + + /* return to application */ + return (out); + } + + /** + * @} end of BilinearInterpolate group + */ + |