Question

C语言打开图像文件后读取像素

Answer 1

C语言打开图像文件后运用以下代码就可以读取像素，具体如下：
#ifndef IMAGE_H
#define IMAGE_H
void image_info(FILE* file);
void image_save(FILE *file);
void image_gray();
void image_binarization();
void image_opposite();
void image_channel(); //抽取RGB通道
void image_bright();//改变图像亮度

typedef struct BMP
{
//14字节
unsigned short bfType; //文件标识 2字节 必须为BM
unsigned int bfSize; //文件大小 4字节
unsigned short bfReserved1; //保留，每字节以"00"填写 2字节
unsigned short bfReserved2; //同上 2字节
unsigned int bfOffBits; //记录图像数据区的起始位置(图象数据相对于文件头字节的偏移量)。 4字节

//40字节
unsigned int biSize; //表示本结构的大小 4字节
int biWidth; //位图的宽度 4字节
int biHeight; //位图的高度 4字节
unsigned short biPlanes; //永远为1 , 2字节
unsigned short biBitCount; //位图的位数 分为1 4 8 16 24 32 2字节
unsigned int biCompression; //压缩说明 4字节
unsigned int biSizeImage; //表示位图数据区域的大小以字节为单位 4字节
int biXPelsPerMeter; //用象素/米表示的水平分辨率 4字节
int biYPelsPerMeter; //用象素/米表示的垂直分辨率 4字节
unsigned int biClrUsed; //位图使用的颜色索引数 4字节
unsigned int biClrImportant; //对图象显示有重要影响的颜色索引的数目 4字节

} BMP;

int line_byte;
unsigned char *imagedata;
extern BMP bmp;
extern int line_byte;
extern unsigned char *imagedata;
#endif

//image_rw.c文件

#include<stdio.h>
#include<stdlib.h>
#include"image.h"

void image_info(FILE *file)
{

int times=3; //输入文件名次数。
char bmp_name[10]; //文件名

printf("\nplease enter a file name for reading:");
do
{
if (times<3)
{
printf("\nplease enter a file name for reading again:");
}
fflush(stdin);
gets(bmp_name);
//printf("\n%s",bmp_name);
file=fopen(bmp_name,"rb+"); //打开一个文件进行读写操作。
--times;
if (file==NULL)
{
printf("\nerror opening %s for reading! ",bmp_name);
}
else
{
break;
}
}
while(times!=0);

if (times==0)
{
printf("\nsorry, shutdown!");
exit(1);
}

//读取图像信息

fseek(file,0L,0); //读取图像文件类型
fread(&bmp,sizeof(BMP),1,file);
printf("\n bmp tpye: %u",bmp.bfType);
printf("\n bmp size: %u",bmp.bfSize);
printf("\n bmp reserved1: %u",bmp.bfReserved1);
printf("\n bmp reserved2: %u",bmp.bfReserved2);
printf("\n bmp offBits: %u",bmp.bfOffBits);

printf("\n bmp bisize: %u",bmp.biSize);
printf("\n bmp biWidth: %d",bmp.biWidth);
printf("\n bmp biHeight: %d",bmp.biHeight);
printf("\n bmp biplans: %u",bmp.biPlanes);
printf("\n bmp biBitCount: %u",bmp.biBitCount);
printf("\n bmp biCompression: %u",bmp.biCompression);
printf("\n bmp biSizeImage: %u",bmp.biSizeImage);
printf("\n bmp biXPelsPerMeter: %d",bmp.biXPelsPerMeter);
printf("\n bmp biYPelsPerMeter: %d",bmp.biYPelsPerMeter);
printf("\n bmp biClrUsed: %u",bmp.biClrUsed);
printf("\n bmp biClrImportant: %u\n",bmp.biClrImportant);

line_byte=(bmp.biWidth*bmp.biBitCount/8+3)/4*4; //获得图像数据每行的数据个数
//printf("dfsa%u",bmp.line_byte);
//bmp.imagedata=NULL;
imagedata=(unsigned char*)malloc(bmp.biSizeImage);

fseek(file,(long)bmp.bfOffBits,0);
fread(imagedata,sizeof(unsigned char),bmp.biSizeImage,file);

fclose(file);
}

//保存图像
void image_save(FILE *file)
{
int times=3; //输入文件名次数。
char bmp_name[10]; //文件名
//int i; //记录数据区个数

printf("\nplease enter a file name for writeing:");
do
{
if (times<3)
{
printf("\nplease enter a file name for writeing again:");
}
fflush(stdin);
gets(bmp_name);
printf("\n%s",bmp_name);
file=fopen(bmp_name,"wb+"); //打开一个文件进行读写操作。
--times;
if (file==NULL)
{
printf("\nerror opening %s for writing",bmp_name);
}
else
{
break;
}
}
while(times!=0);

if (times==0)
{
printf("\nsorry, shutdown!");
exit(1);
}

//写文件头
printf("\n%s",bmp_name);
fseek(file,0L,0); //图像文件类型
fwrite(&(bmp.bfType),sizeof(short),1,file);
printf("\n bmp tpye: %d",bmp.bfType);

fseek(file,2L,0); //图像文件大小
fwrite(&(bmp.bfSize),sizeof(int),1,file);
printf("\n bmp size: %d",bmp.bfSize);

fseek(file,6L,0); //图像文件保留字1
fwrite(&(bmp.bfReserved1),sizeof(short),1,file);
printf("\n bmp reserved1: %d",bmp.bfReserved1);

fseek(file,8L,0); //图像文件保留字2
fwrite(&(bmp.bfReserved2),sizeof(short),1,file);
printf("\n bmp reserved2: %d",bmp.bfReserved2);

fseek(file,10L,0);//数据区的偏移量
fwrite(&(bmp.bfOffBits),sizeof(short),1,file);
printf("\n bmp offBits: %d",bmp.bfOffBits);

fseek(file,14L,0);//文件头结构大小
fwrite(&(bmp.biSize),sizeof(int),1,file);
printf("\n bmp bisize: %d",bmp.biSize);

fseek(file,18L,0);//图像的宽度
fwrite(&(bmp.biWidth),sizeof(int),1,file);
printf("\n bmp biWidth: %d",bmp.biWidth);

fseek(file,22L,0);//图像的高度
fwrite(&(bmp.biHeight),sizeof(int),1,file);
printf("\n bmp biHeight: %d",bmp.biHeight);

fseek(file,24L,0);//图像的面数
fwrite(&(bmp.biPlanes),sizeof(short),1,file);
printf("\n bmp biplans: %d",bmp.biPlanes);

fseek(file,28L,0);//图像一个像素的字节数
fwrite(&(bmp.biBitCount),sizeof(short),1,file);
printf("\n bmp biBitCount: %d",bmp.biBitCount);

fseek(file,30L,0);//图像压缩信息
fwrite(&(bmp.biCompression),sizeof(short),1,file);
printf("\n bmp biCompression: %d",bmp.biCompression);

fseek(file,34L,0);//图像数据区的大小
fwrite(&(bmp.biSizeImage),sizeof(int),1,file);
printf("\n bmp biSizeImage: %d",bmp.biSizeImage);

fseek(file,38L,0);//水平分辨率
fwrite(&(bmp.biXPelsPerMeter),sizeof(int),1,file);
printf("\n bmp biXPelsPerMeter: %d",bmp.biXPelsPerMeter);

fseek(file,42L,0);//垂直分辨率
fwrite(&(bmp.biYPelsPerMeter),sizeof(int),1,file);
printf("\n bmp biYPelsPerMeter: %d",bmp.biYPelsPerMeter);

fseek(file,46L,0);//颜色索引数
fwrite(&(bmp.biClrUsed),sizeof(int),1,file);
printf("\n bmp biClrUsed: %d",bmp.biClrUsed);

fseek(file,50L,0);//重要颜色索引数
fwrite(&(bmp.biClrImportant),sizeof(int),1,file);
printf("\n bmp biClrImportant: %d\n",bmp.biClrImportant);

fseek(file,(long)(bmp.bfOffBits),0);
fwrite(imagedata,sizeof(unsigned char),bmp.biSizeImage,file);

fclose(file);
}

//pixProcess.c文件

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include"image.h"

//灰度化
void image_gray()
{
int i,j;
unsigned char tmp;
for (i=0;i<bmp.biHeight;i++)
{
for (j=0;j<line_byte/3;j++)
{
tmp=0.11*(*(imagedata+i*line_byte+j*3+0))+0.59*(*(imagedata+i*line_byte+j*3+1))+0.3*(*(imagedata+i*line_byte+j*3+2));
imagedata[i*line_byte+j*3+0]=tmp;
imagedata[i*line_byte+j*3+1]=tmp;
imagedata[i*line_byte+j*3+2]=tmp;
//printf("\nnidsfh%d %d",i,j);
}
}
}

//二值化

void image_binarization()
{
int i,j;
for (i=0;i<bmp.biHeight;i++)
{
for (j=0;j<line_byte;j++)
{
if ((*(imagedata+i*line_byte+j))<128)
{
imagedata[i*line_byte+j]=0;
}
else
{
imagedata[i*line_byte+j]=255;
}
}
}
}

void image_opposite() //反相
{
int i,j;
for (i=0;i<bmp.biHeight;i++)
{
for (j=0;j<line_byte;j++)
{
imagedata[i*line_byte+j]=abs(255-imagedata[i*line_byte+j]);
}
}
}

void image_channel() //抽取RGB通道
{
int i,j;
char rgb;
printf("\nplease enter a char(r/g/b): ");
fflush(stdin);
scanf("%c",&rgb);
if (rgb=='b')
{
for (i=0;i<bmp.biHeight;i++)
{
for (j=0;j<line_byte/3;j++)
{
imagedata[i*line_byte+3*j+1]=0;
imagedata[i*line_byte+3*j+2]=0;
}
}
}
else if(rgb=='g')
{
for (i=0;i<bmp.biHeight;i++)
{
for (j=0;j<line_byte/3;j++)
{
imagedata[i*line_byte+3*j]=0;
imagedata[i*line_byte+3*j+2]=0;
}
}
}
else
{
for (i=0;i<bmp.biHeight;i++)
{
for (j=0;j<line_byte/3;j++)
{
imagedata[i*line_byte+3*j]=0;
imagedata[i*line_byte+3*j+1]=0;
}
}
}

}

void image_bright()//改变图像亮度
{
int level;
int i,j;
printf("\n please enter the level of brightness[-255 to 255] :");
fflush(stdin);
scanf("%d",&level);
for (i=0;i<bmp.biHeight;i++)
{
for (j=0;j<line_byte;j++)
{
if (level>=0)
{

if ((imagedata[i*line_byte+j]+level)>255)
imagedata[i*line_byte+j]=255;
else
imagedata[i*line_byte+j]+=level;
}
else
{
if ((imagedata[i*line_byte+j]-abs(level))<0)
imagedata[i*line_byte+j]=0;
else
imagedata[i*line_byte+j]+=level;
}

}
}
}

//void image_create() //创建一幅24位BMP图像文件。
//{

//main.c文件

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<conio.h>
#include"image.h"

BMP bmp;

int main()
{
FILE *file=NULL;
int choose;
char gono;
do
{
image_info(file); //imagedata已经分配了动态内存，但是没有释放

printf("\n 1.image_opposite");
printf("\n 2.image_gray");
printf("\n 3.image_binarization");
printf("\n 4.image_channel");
printf("\n 5.image_brightness");
//printf("6.image_opposite");
//printf("7.image_opposite");

printf("\nchoose your options:");
fflush(stdin);
scanf("%d",&choose);
switch(choose)
{

case 1:
image_opposite();
image_save(file);
free(imagedata);
break;
case 2:
image_gray();
image_save(file);
free(imagedata);
break;
case 3:
image_binarization();
image_save(file);
free(imagedata);
break;
case 4:
image_channel();
image_save(file);
free(imagedata);
break;
case 5:
image_bright();
image_save(file);
free(imagedata);
break;
default:
printf("\n wrong choose!");

}

printf("\nlet's go on?(y/n):");
fflush(stdin);
scanf("%c",&gono);
if (gono=='n')
{
printf("\nbye bye!");
break;
}
}
while(1);

return 0;
}

Answer 2

不同的图像文件格式不一样，去研究一下你要打开图像的格式就很好做了。

Answer 3

循环256次，用UINT *buf，申请空间，依次独处像素点。

Answer 4

用bitmap加载图像，然後用linescan效率比较高。