c读取bmp文件时遇到的问题

[forestfire]

大家好 我最近在学习用c读取bmp文件,遇到了一些问题 ，请大家帮帮我：
1.一副256色320*200的bmp文件，按一些书籍里介绍，文件头信息区有54个字节，调色板有1024kb，图像存储区的大小是320*200个字节
而 （320*200+1024+54)/1024=63.5kb+54B ，但是为什么在电脑里这样的图片显示的是63.5kb呢？？

2.调色板有什么作用？既然可以用 语句video_buffer[(y<<8)+(y<<6)+x]= color;来显示坐标（x,y),那是否可以循环读取图像存储区的一个字节给color，用上面的语句显示呢？
3.下面是我在TC2.0下调试的源文件
运行倒语句 read(fp,&video_buffer[i*SCREEN_WIDTH],SCREEN_WIDTH);时，屏幕不会发生变化
在编译时此语句有一个warming：suspicious pointer convers in Funcion_ BMP_Load_Screen;

#include<io.h>
#include<stdio.h>
#include<dos.h>
#include<string.h>
#include<math.h>
#include<stdio.h>
#include<bios.h>
#include<mem.h>
#include<fcntl.h>
#include<stdlib.h>
#include<conio.h>

#define SCREEN_HEIGHT 200
#define SCREEN_WIDTH 320

#define PALETTE_MASK 0x3c6
#define PALETTE_REGISTER_RD 0x3c7
#define PALETTE_REGISTER_WR 0x3c8
#define PALETTE_DATA 0x3c9

#define VGA256 0x13
#define TEXT_MODE 0x03

unsigned char far *video_buffer=(char far *)0xA0000000L;

typedef struct BMP_file
{
unsigned int bfType;
unsigned long bfSize;
unsigned int Reserved1;
unsigned int reserved2;
unsigned long bfOffset;
}
bitmapfile;

typedef struct BMP_info
{
unsigned long biSize;
unsigned long biWidth;
unsigned long biHeight;
unsigned int biPlanes;
unsigned int biBitCount;
unsigned long biCompression;
unsigned long biSizeImage;
unsigned long biXpolsPerMeter;
unsigned long biYpelsPerMeter;
unsigned long biClrUsed;
unsigned long biClrImportant;
}
bitmapinfo;


typedef struct RGB_BMP_typ
{
unsigned char blue;
unsigned char green;
unsigned char red;
unsigned char reserved;
}RGB_BMP,*RGB_BMP_ptr;

typedef struct bmp_picture_typ
{
bitmapfile file;
bitmapinfo info;
RGB_BMP palette[256];
char far *buffer;


} bmp_picture, *bmp_picture_ptr;

void Set_BMP_Palette_Register(int index,RGB_BMP_ptr color)
{
outp(PALETTE_MASK,0xff);
outp(PALETTE_REGISTER_WR,index);
outp(PALETTE_DATA,color->red);
outp(PALETTE_DATA,color->green);
outp(PALETTE_DATA,color->blue);
}

void Check_Bmp(bmp_picture_ptr bmp_ptr)
{
if(bmp_ptr->file.bfType!=0x4d42)
{
printf("Not a BMP file!\n");
exit(1);
}
if(bmp_ptr->info.biCompression!=0)
{
printf("Can not display a compressed BMP file!\n");
exit(1);
}
if(bmp_ptr->info.biBitCount!=8)
{
printf("Not a index 16color BMP file!\n");

exit(1);
}
}


void BMP_Load_Screen(char *bmp);

{
int i,fp;
bmp_picture bmp256;
char *file_name;
if ((fp=open(bmp,O_RDONLY))==1)
return;

read(fp,&bmp256.file,sizeof(bitmapfile));
read(fp,&bmp256.info,sizeof(bitmapinfo));

Check_Bmp((bmp_picture_ptr)&bmp256);
/*u can ingore it */
/*lseek(fp,54,0); */

for (i=0;i<256;i++)
{
read(fp,&bmp256.palette[i].blue,1);
read(fp,&bmp256.palette[i].green,1);
read(fp,&bmp256.palette[i].red,1);
read(fp,&bmp256.palette[i].reserved,1);
bmp256.palette[i].blue=bmp256.palette[i].blue>>2;
bmp256.palette[i].green=bmp256.palette[i].green>>2;
bmp256.palette[i].red=bmp256.palette[i].red>>2;
}
for (i=0;i<256;i++)
Set_BMP_Palette_Register(i,(RGB_BMP_ptr)&bmp256.palette[i]);

for(i=SCREEN_HEIGHT-1;i>=0;i--)
{
lseek(fp,1078+(long)(SCREEN_HEIGHT-i-1)*SCREEN_WIDTH,0);
read(fp,&video_buffer[i*SCREEN_WIDTH],SCREEN_WIDTH);
}
close(fp);

}

void Set_Video_Mode(int mode)
{
union REGS inregs,outregs;
inregs.h.ah=0;
inregs.h.al=(unsigned char)mode;
int86(0x10,&inregs,&outregs);
}

int main()
{
Set_Video_Mode(VGA256);
BMP_Load_Screen("256.bmp");
getch();

Set_Video_Mode(TEXT_MODE);

}

[forestfire]

兄弟们 ， 我通过以下的修改，将上面的图片读入成功 ，但是为什么用那个软件转化的图片读出来的只是一些轮廓，修改部分我标明了
顺便附带两张图片 自己可以看运行的结果
#include<io
#include<stdio.h>
#include<dos.h>
#include<string.h>
#include<math.h>
#include<stdio.h>
#include<bios.h>
#include<mem.h>
#include<fcntl.h>
#include<stdlib.h>
#include<conio.h>

#define SCREEN_HEIGHT 200
#define SCREEN_WIDTH 320

#define PALETTE_MASK 0x3c6
#define PALETTE_REGISTER_RD 0x3c7
#define PALETTE_REGISTER_WR 0x3c8
#define PALETTE_DATA 0x3c9

#define VGA256 0x13
#define TEXT_MODE 0x03

unsigned char far *video_buffer=(char far *)0xA0000000L;

typedef struct BMP_file
{
unsigned int bfType;
unsigned long bfSize;
unsigned int Reserved1;
unsigned int reserved2;
unsigned long bfOffset;
}
bitmapfile;

typedef struct BMP_info
{
unsigned long biSize;
unsigned long biWidth;
unsigned long biHeight;
unsigned int biPlanes;
unsigned int biBitCount;
unsigned long biCompression;
unsigned long biSizeImage;
unsigned long biXpolsPerMeter;
unsigned long biYpelsPerMeter;
unsigned long biClrUsed;
unsigned long biClrImportant;
}
bitmapinfo;


typedef struct RGB_BMP_typ
{
unsigned char blue;
unsigned char green;
unsigned char red;
unsigned char reserved;
}RGB_BMP,*RGB_BMP_ptr;

typedef struct bmp_picture_typ
{
bitmapfile file;
bitmapinfo info;
RGB_BMP palette[256];
char far *buffer;

} bmp_picture, *bmp_picture_ptr;

void Set_BMP_Palette_Register(int index,RGB_BMP_ptr color)
{
outportb(PALETTE_MASK,0xff);
outportb(PALETTE_REGISTER_WR,index);
outportb(PALETTE_DATA,color->red);
outportb(PALETTE_DATA,color->green);
outportb(PALETTE_DATA,color->blue);
}

void Check_Bmp(bmp_picture_ptr bmp_ptr)
{
if(bmp_ptr->file.bfType!=0x4d42)
{
printf("Not a BMP file!\n");
exit(1);
}
if(bmp_ptr->info.biCompression!=0)
{
printf("Can not display a compressed BMP file!\n");
exit(1);
}
if(bmp_ptr->info.biBitCount!=8)
{
printf("Not a index 16color BMP file!\n");

exit(1);
}
}


void BMP_Load_Screen(char *bmp)
{
FILE *fp;
int i; char m; int j;
bmp_picture bmp256;
char *file_name;
if ((fp=fopen(bmp,"r"))==NULL)
exit(1);

fread( &bmp256.file,sizeof(bitmapfile),1,fp);
fread( &bmp256.info,sizeof(bitmapinfo),1,fp);

Check_Bmp((bmp_picture_ptr)&bmp256);
/*u can ingore it */
fseek(fp,54,0);

for (i=0;i<256;i++)
{
fread( &bmp256.palette[i].blue,sizeof(char),1,fp);
fread( &bmp256.palette[i].green,sizeof(char),1,fp);
fread( &bmp256.palette[i].red,sizeof(char),1,fp);
fread( &bmp256.palette[i].reserved,sizeof(char),1,fp);
bmp256.palette[i].blue=bmp256.palette[i].blue>>2;
printf(" %d ",bmp256.palette[i].blue);
bmp256.palette[i].green=bmp256.palette[i].green>>2;
printf( " %d ",bmp256.palette[i].green);
bmp256.palette[i].red=bmp256.palette[i].red>>2;
printf(" %d ",bmp256.palette[i].red);
if(i%9==0)
printf("\n");
}
for (i=0;i<256;i++)
Set_BMP_Palette_Register(i,(RGB_BMP_ptr)&bmp256.palette[i]);

for(i=SCREEN_HEIGHT-1;i>=0;i--)
{
fseek( fp,1078+(long)(SCREEN_HEIGHT-i-1)*SCREEN_WIDTH,0);
for(j=0;j<SCREEN_WIDTH;j++)
{/*以下是修改部分*/
fread( &m,sizeof(char),1,fp);
video_buffer[i*SCREEN_WIDTH+j]=m;
}
}
fclose(fp);

}

void Set_Video_Mode(int mode)
{
union REGS inregs,outregs;
inregs.h.ah=0;
inregs.h.al=(unsigned char)mode;
int86(0x10,&inregs,&outregs);
}

int main()
{ /* int gdriver=6,gmode;
gmode=0;*/
/* initgraph(gdriver,gmode,""); */
Set_Video_Mode(VGA256);
/* circle(320,240,20);*/
BMP_Load_Screen("cjl.bmp");
getch();
delay(1000);

Set_Video_Mode(TEXT_MODE);
getchar();
return 0;
}

[forestfire]

[forestfire]

这是以上两个图像文件，大家可以在主程序里修改文件名来读取不同的文件