使用numpy內核并在從python呼叫的C函式中的矩陣上填充的邊界問題-有解無憂

我想使用外部 c 函式對影像進行 numpy 內核操作。為此，目標是僅在填充內遍歷影像影像，以便內核不會超出影像。1在下面的除錯代碼中，我首先生成了一個在 python 腳本中填充的矩陣。然后我將這個矩陣及其維度傳遞給 c 函式。我遍歷行和列，并希望將值設定為9是否在矩陣的邊界（在填充中）以及8是否在我想要進行計算的矩陣部分內。

計算的最終目標是對矩陣的每個條目進行計算，并為該計算獲取所有鄰居（例如，在 3x3 矩陣模式上）。對于 3x3 矩陣，搜索必須在第一行/列之后的停止之前開始，并在最后一行列之前停止。

我想要的結果如下：

,0,1,2,3
0,9,9,9,9
1,9,8,8,9
2,9,8,8,9
3,9,9,9,9

相反，我得到以下資訊：

,0,1,2,3
0,9,9,9,9
1,8,8,8,8
2,8,8,8,8
3,8,1,1,1

這是.sh腳本debug_scriptsh.sh：

a=debug_scriptc && cc -fPIC -shared -o $a.so $a.c && python debug_scriptpy.py && open debug_table.csv

.py腳本debug_scriptc.c：_

import ctypes
import pandas as pd
import numpy as np
import sys
import pdb

DLL_NAME = "./debug_scriptc.{:s}".format("dll" if sys.platform[:3].lower() == "win" else "so")

def np_mat_type(rows, cols, element_type=float):
  return np.ctypeslib.ndpointer(dtype=element_type, shape=(rows, cols), flags="C_CONTIGUOUS")

rows0 = 4
cols0 = 4
kernel_size = 3

dll = ctypes.CDLL(DLL_NAME)
matrix_func = dll.matrixFunc4matin
matrix_func.argtypes = (
    ctypes.c_size_t,
    np_mat_type(rows0, cols0), 
    ctypes.c_size_t, 
    ctypes.c_size_t
    )
matrix_func.restype = np_mat_type(rows0, cols0)

dealloc_array = dll.deallocArray
dealloc_array.argtypes = (np_mat_type(rows0, cols0),)
dealloc_array.restype = None
u_rms_array = np.zeros((rows0, cols0))

velocity_image_ones = np.empty((rows0, cols0))
velocity_image_ones[:] = 1

u_rms_array = matrix_func(
    kernel_size, 
    velocity_image_ones,
    rows0, 
    cols0 
    )
debug_DF_u_rms_array_C = pd.DataFrame(u_rms_array.astype(int))
debug_DF_u_rms_array_C.to_csv("debug_table.csv")
dealloc_array(u_rms_array)

.c腳本debug_scriptc.c：_


#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#if defined(_WIN32)
#  define DLL00_EXPORT_API __declspec(dllexport)
#else
#  define DLL00_EXPORT_API
#endif

#define ELEMENT_TYPE double

#if defined(__cplusplus)
extern "C" {
#endif

DLL00_EXPORT_API ELEMENT_TYPE* matrixFunc4matin(
  size_t kernel_size,
  const ELEMENT_TYPE *pvelocity_image_ones, 
  size_t rows0, 
  size_t cols0
  );
DLL00_EXPORT_API void deallocArray(ELEMENT_TYPE *pMat);

#if defined(__cplusplus)
}
#endif

ELEMENT_TYPE* matrixFunc4matin(
  size_t kernel_size,
  const ELEMENT_TYPE *pvelocity_image_ones, 
  size_t rows0, 
  size_t cols0 
  )

{
  size_t matSize = sizeof(ELEMENT_TYPE) * cols0 * rows0;
  ELEMENT_TYPE *pRet = (ELEMENT_TYPE*)(malloc(matSize));

  memcpy(pRet, pvelocity_image_ones, matSize);  

  int start_kern_search = kernel_size - 2;
  int end_kern_search_rows = rows0 - (kernel_size-1)/2;
  int end_kern_search_cols = cols0 - (kernel_size-1)/2;

  for (int i_velmap = 0; i_velmap < rows0; i_velmap  ){  
    for (int j_velmap = 0; j_velmap < cols0; j_velmap  ){  
      if (i_velmap < start_kern_search | i_velmap > end_kern_search_rows | j_velmap < start_kern_search | j_velmap > end_kern_search_cols){
        pRet[i_velmap * cols0   j_velmap] = 9;
        continue;
      }
      else
      {
        pRet[i_velmap * end_kern_search_cols   j_velmap] = 8;
      }
    }
  }
  return pRet;
}


void deallocArray(ELEMENT_TYPE *pMat)
{
    if (pMat)
        free(pMat);
}

uj5u.com熱心網友回復：

[SO]的繼續：如何在 C 中撰寫一個函式，該函式將兩個矩陣作為輸入作為 numpy array。

問題是指數計算。
當將（小）矩形（內部）構圖（居中）成較大的矩形（外部）時，邊緣公式（在每個軸（維度）上）為：

edge = (outer_dim - inner_dim) / 2

dll00.c：

#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#if defined(_WIN32)
#  define DLL00_EXPORT_API __declspec(dllexport)
#else
#  define DLL00_EXPORT_API
#endif

#define ELEMENT_TYPE double

#if defined(__cplusplus)
extern "C" {
#endif

DLL00_EXPORT_API ELEMENT_TYPE* matrixFormat(const ELEMENT_TYPE *pMat, size_t rows, size_t cols, size_t kernel);
DLL00_EXPORT_API void deallocArray(ELEMENT_TYPE *pMat);

#if defined(__cplusplus)
}
#endif

#define MIN_EDGE 1
#define PAD_VAL 9
#define KERNEL_VAL 8


static size_t edge(size_t dim, size_t kernel, size_t minEdge)
{
    if (kernel >= dim)
        return minEdge;
    size_t ret = (dim - kernel) / 2;
    return (ret > minEdge) ? ret : minEdge;
}


ELEMENT_TYPE* matrixFormat(
    const ELEMENT_TYPE *pMat,
    size_t rows,
    size_t cols,
    size_t kernel)
{
    size_t matSize = sizeof(ELEMENT_TYPE) * cols * rows;
    ELEMENT_TYPE *pRet = (ELEMENT_TYPE*)(malloc(matSize));

    printf("\nC: - matrix (%zu X %zu (%zu)):\n", rows, cols, kernel);
    size_t minRow = edge(rows, kernel, MIN_EDGE),
           minCol = edge(cols, kernel, MIN_EDGE);
    size_t maxRow = rows - minRow - 1,
           maxCol = cols - minCol - 1;
    for (size_t i = 0; i < rows;   i) {
        for (size_t j = 0; j < cols;   j) {
            pRet[i * cols   j] = ((i >= minRow) && (i <= maxRow) && (j >= minCol) && (j <= maxCol)) ? KERNEL_VAL : PAD_VAL;
        }
    }
    return pRet;
}


void deallocArray(ELEMENT_TYPE *pMat)
{
    if (pMat)
        free(pMat);
}

代碼00.py：

#!/usr/bin/env python

import ctypes as cts
import sys

import numpy as np


DLL_NAME = "./dll00.{:s}".format("dll" if sys.platform[:3].lower() == "win" else "so")

ELEMENT_TYPE = cts.c_double


def np_mat_type(rows, cols, element_type=ELEMENT_TYPE):
    return np.ctypeslib.ndpointer(dtype=element_type, shape=(rows, cols), flags="C_CONTIGUOUS")


def main(*argv):
    np.set_printoptions(precision=3)

    dll = cts.CDLL(DLL_NAME)
    matrix_format = dll.matrixFormat
    dealloc_array = dll.deallocArray
    dealloc_array.restype = None

    values = (
        (4, 4, 3),
        (6, 6, 3),
        #(3, 3, 3),
    )

    for rows, cols, kernel in values:
        print("\nRows: {:d}, Cols: {:d}, Kernel: {:d}".format(rows, cols, kernel))
        mat = np.ones((rows, cols), dtype=ELEMENT_TYPE)

        matrix_format.argtypes = (np_mat_type(rows, cols), cts.c_size_t, cts.c_size_t, cts.c_size_t)
        matrix_format.restype = np_mat_type(rows, cols)
        dealloc_array.argtypes = (np_mat_type(rows, cols),)

        print("mat:")
        print(mat)
        mat_res = matrix_format(mat, rows, cols, kernel)
        print("result:")
        print(mat_res)

        dealloc_array(mat_res)


if __name__ == "__main__":
    print("Python {:s} {:03d}bit on {:s}\n".format(" ".join(elem.strip() for elem in sys.version.split("\n")),
                                                   64 if sys.maxsize > 0x100000000 else 32, sys.platform))
    rc = main(*sys.argv[1:])
    print("\nDone.\n")
    sys.exit(rc)

輸出：

(qaic-env) [cfati@cfati-5510-0:/mnt/e/Work/Dev/StackOverflow/q074171783]> ~/sopr.sh
### Set shorter prompt to better fit when pasted in StackOverflow (or other) pages ###

[064bit prompt]> ls
code00.py  dll00.c
[064bit prompt]> gcc -fPIC -shared -o dll00.so dll00.c
[064bit prompt]> ls
code00.py  dll00.c  dll00.so
[064bit prompt]> python ./code00.py
Python 3.8.10 (default, Jun 22 2022, 20:18:18) [GCC 9.4.0] 064bit on linux


Rows: 4, Cols: 4, Kernel: 3
mat:
[[1. 1. 1. 1.]
 [1. 1. 1. 1.]
 [1. 1. 1. 1.]
 [1. 1. 1. 1.]]

C: - matrix (4 X 4 (3)):
result:
[[9. 9. 9. 9.]
 [9. 8. 8. 9.]
 [9. 8. 8. 9.]
 [9. 9. 9. 9.]]

Rows: 6, Cols: 6, Kernel: 3
mat:
[[1. 1. 1. 1. 1. 1.]
 [1. 1. 1. 1. 1. 1.]
 [1. 1. 1. 1. 1. 1.]
 [1. 1. 1. 1. 1. 1.]
 [1. 1. 1. 1. 1. 1.]
 [1. 1. 1. 1. 1. 1.]]

C: - matrix (6 X 6 (3)):
result:
[[9. 9. 9. 9. 9. 9.]
 [9. 8. 8. 8. 8. 9.]
 [9. 8. 8. 8. 8. 9.]
 [9. 8. 8. 8. 8. 9.]
 [9. 8. 8. 8. 8. 9.]
 [9. 9. 9. 9. 9. 9.]]

Done.

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