所有人，今日作业：用fwrite 和 fseek功能，将一张bmp格式的图片更改成 德国国旗

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(int argc, const char *argv[])
{
	FILE* fp=fopen("./rising_freedom(复件).bmp","r");
	fseek(fp,2,SEEK_SET);
	int bmp_size=0;
	fread(&bmp_size,4,1,fp);
	printf("%d\n",bmp_size);
	int bmp_w=0;
	int bmp_h=0;
	fseek(fp,18,SEEK_SET);
	fread(&bmp_w,4,1,fp);
	fread(&bmp_h,4,1,fp);
	printf("图像像素信息为: %d*%d\n",bmp_w,bmp_h);
	fclose(fp);
	FILE* fp2=fopen("./rising_freedom(复件).bmp","r+");
	fseek(fp2,54,SEEK_SET);
	unsigned char bgr1[3]={0,0,0};//black
	unsigned char bgr2[3]={0,0,255};//red
	unsigned char bgr3[3]={0,255,255};//yellow

	for(int j=0;j<bmp_h;j++){
		for(int i=0;i<bmp_w;i++){
			if(j>=0&&j<(bmp_h/3)){
				fwrite(bgr1,3,1,fp2);
			}
			if(j>=(bmp_h/3)&&j<(bmp_h/3*2)){
				fwrite(bgr2,3,1,fp2);
			}
			if(j>=(bmp_h/3*2)&&j<bmp_h){
				fwrite(bgr3,3,1,fp2);
			}
		}	
	}
	fclose(fp2);
	return 0;
}