c语言一维中值滤波函数 中值滤波c代码

c语言中值滤波问题？

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C语言实现fir1函数

#include stdio.h

#ifdef WIN32

#include conio.h

#endif

#define SAMPLE double /* define the type used for data samples */

void clear(int ntaps, SAMPLE z[])

{

int ii;

for (ii = 0; ii ntaps; ii++) {

z[ii] = 0;

}

}

SAMPLE fir_basic(SAMPLE input, int ntaps, const SAMPLE h[], SAMPLE z[])

{

int ii;

SAMPLE accum;

/* store input at the beginning of the delay line */

z[0] = input;

/* calc FIR */

accum = 0;

for (ii = 0; ii ntaps; ii++) {

accum += h[ii] * z[ii];

}

/* shift delay line */

for (ii = ntaps - 2; ii = 0; ii--) {

z[ii + 1] = z[ii];

}

return accum;

}

SAMPLE fir_circular(SAMPLE input, int ntaps, const SAMPLE h[], SAMPLE z[],

int *p_state)

{

int ii, state;

SAMPLE accum;

state = *p_state; /* copy the filter's state to a local */

/* store input at the beginning of the delay line */

z[state] = input;

if (++state = ntaps) { /* incr state and check for wrap */

state = 0;

}

/* calc FIR and shift data */

accum = 0;

for (ii = ntaps - 1; ii = 0; ii--) {

accum += h[ii] * z[state];

if (++state = ntaps) { /* incr state and check for wrap */

state = 0;

}

}

*p_state = state; /* return new state to caller */

return accum;

}

SAMPLE fir_shuffle(SAMPLE input, int ntaps, const SAMPLE h[], SAMPLE z[])

{

int ii;

SAMPLE accum;

/* store input at the beginning of the delay line */

z[0] = input;

/* calc FIR and shift data */

accum = h[ntaps - 1] * z[ntaps - 1];

for (ii = ntaps - 2; ii = 0; ii--) {

accum += h[ii] * z[ii];

z[ii + 1] = z[ii];

}

return accum;

}

SAMPLE fir_split(SAMPLE input, int ntaps, const SAMPLE h[], SAMPLE z[],

int *p_state)

{

int ii, end_ntaps, state = *p_state;

SAMPLE accum;

SAMPLE const *p_h;

SAMPLE *p_z;

/* setup the filter */

accum = 0;

p_h = h;

/* calculate the end part */

p_z = z + state;

*p_z = input;

end_ntaps = ntaps - state;

for (ii = 0; ii end_ntaps; ii++) {

accum += *p_h++ * *p_z++;

}

/* calculate the beginning part */

p_z = z;

for (ii = 0; ii state; ii++) {

accum += *p_h++ * *p_z++;

}

/* decrement the state, wrapping if below zero */

if (--state 0) {

state += ntaps;

}

*p_state = state; /* return new state to caller */

return accum;

}

SAMPLE fir_double_z(SAMPLE input, int ntaps, const SAMPLE h[], SAMPLE z[],

int *p_state)

{

SAMPLE accum;

int ii, state = *p_state;

SAMPLE const *p_h, *p_z;

/* store input at the beginning of the delay line as well as ntaps more */

z[state] = z[state + ntaps] = input;

/* calculate the filter */

p_h = h;

p_z = z + state;

accum = 0;

for (ii = 0; ii ntaps; ii++) {

accum += *p_h++ * *p_z++;

}

/* decrement state, wrapping if below zero */

if (--state 0) {

state += ntaps;

}

*p_state = state; /* return new state to caller */

return accum;

}

SAMPLE fir_double_h(SAMPLE input, int ntaps, const SAMPLE h[], SAMPLE z[],

int *p_state)

{

SAMPLE accum;

int ii, state = *p_state;

SAMPLE const *p_h, *p_z;

/* store input at the beginning of the delay line */

z[state] = input;

/* calculate the filter */

p_h = h + ntaps - state;

p_z = z;

accum = 0;

for (ii = 0; ii ntaps; ii++) {

accum += *p_h++ * *p_z++;

}

/* decrement state, wrapping if below zero */

if (--state 0) {

state += ntaps;

}

*p_state = state; /* return new state to caller */

return accum;

}

int main(void)

{

#define NTAPS 6

static const SAMPLE h[NTAPS] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };

static SAMPLE h2[2 * NTAPS];

static SAMPLE z[2 * NTAPS];

#define IMP_SIZE (3 * NTAPS)

static SAMPLE imp[IMP_SIZE];

SAMPLE output;

int ii, state;

/* make impulse input signal */

clear(IMP_SIZE, imp);

imp[5] = 1.0;

/* create a SAMPLEd h */

for (ii = 0; ii NTAPS; ii++) {

h2[ii] = h2[ii + NTAPS] = h[ii];

}

/* test FIR algorithms */

printf("Testing fir_basic:\n ");

clear(NTAPS, z);

for (ii = 0; ii IMP_SIZE; ii++) {

output = fir_basic(imp[ii], NTAPS, h, z);

printf("%3.1lf ", (double) output);

}

printf("\n\n");

printf("Testing fir_shuffle:\n ");

clear(NTAPS, z);

state = 0;

for (ii = 0; ii IMP_SIZE; ii++) {

output = fir_shuffle(imp[ii], NTAPS, h, z);

printf("%3.1lf ", (double) output);

}

printf("\n\n");

printf("Testing fir_circular:\n ");

clear(NTAPS, z);

state = 0;

for (ii = 0; ii IMP_SIZE; ii++) {

output = fir_circular(imp[ii], NTAPS, h, z, state);

printf("%3.1lf ", (double) output);

}

printf("\n\n");

printf("Testing fir_split:\n ");

clear(NTAPS, z);

state = 0;

for (ii = 0; ii IMP_SIZE; ii++) {

output = fir_split(imp[ii], NTAPS, h, z, state);

printf("%3.1lf ", (double) output);

}

printf("\n\n");

printf("Testing fir_double_z:\n ");

clear(2 * NTAPS, z);

state = 0;

for (ii = 0; ii IMP_SIZE; ii++) {

output = fir_double_z(imp[ii], NTAPS, h, z, state);

printf("%3.1lf ", (double) output);

}

printf("\n\n");

printf("Testing fir_double_h:\n ");

clear(NTAPS, z);

state = 0;

for (ii = 0; ii IMP_SIZE; ii++) {

output = fir_double_h(imp[ii], NTAPS, h2, z, state);

printf("%3.1lf ", (double) output);

}

#ifdef WIN32

printf("\n\nHit any key to continue.");

getch();

#endif

return 0;

}

1. fir_basic: 实现基本的FIR滤波器

2. fir_circular: 说明环行buffer是如何实现FIR的。

3. fir_shuffle: 一些TI的处理器上使用的shuffle down技巧

4. fir_split: 把FIR滤波器展开为两块，避免使用环行缓存。

5. fir_double_z: 使用双精度的延迟线，使可以使用一个flat buffer。

6. fir_double_h: 使用双精度的系数，使可以使用一个flat buffer。

c语言中fabs()是什么意思

数学函数:fabs

原型：extern float fabs(float x);

用法：#include math.h

功能：求浮点数x的绝对值

说明：计算|x|, 当x不为负时返回x，否则返回-x

举例：

// fabs.c

#include syslib.h

#include math.h

main()

{

float x;

clrscr(); // clear screen

textmode(0x00); // 6 lines per LCD screen

x=-74.12;

printf("|%f|=%f\n",x,fabs(x));

x=0;

printf("|%f|=%f\n",x,fabs(x));

x=74.12;

printf("|%f|=%f\n",x,fabs(x));

getchar();

return 0;

}

扩展资料：

程序判数滤波 采样的信号,如因常受到随机干扰传感器不稳定而引起严重失真时,可以采用此方法。

方法是:根据生产经验确定两交采样允许的最大偏差△×,若先后两次采样的信号相减数值大于△×,表明输入的是干扰信号,应该去掉;

用上次采样值作为本次采样值,若小于、等于△×表明没有受到干,本次采样值效。该方法适用于慢变化的物理参数的采样,如温度、物理位置等测量系统。

程序判断滤波的C程序函数如下:

float program_detect_filter(float old_new_value[], float X)

{

float sample_value;

if (fabs(old_new_value[1]_old_new_value[0])X)

sample_value=old_new_value[0];

else

sample_value=old_new_value[1];

retrun(sample_value);

}

函数调用需一个一维的两个元素的数组(old_new_value[2],用于存放上次采样值(old_new_value[0],)和本次采样值(old_new_value[1],),函数中sample_value表示有效采样值,X表示根据根据经验确定的两次采样允许的最大偏差△×。

参考资料来源：百度百科：fabs函数