1. 是规定做中值滤波的点不含边缘的点(取决于中值滤波窗口大小)。 2,对图像边缘部分的信息进行镜像处理。
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#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。
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
