Question

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

int main()
{
    unsigned char **T;
    int i,j;
    int H[256];
    FILE *fp=fopen("Collines400300.ima","rb");
    T=(unsigned char**)malloc(300*sizeof(unsigned char*));
    for(i=0;i<400;i++);
    T[i]=(unsigned char*)malloc(400*sizeof(unsigned char));
    while(fp)
    {
        fread(T[i],1,400,fp);

    }


    for(i=0;i<256;i++)
    H[i]=0;


    for(i=0;i<400;i++)
    {
        for(j=0;j<300;j++)
        H[T[i][j]]++;
    }
    for(i=0;i<256;i++)
    printf("%d  ",H[i]);
    return 0;


}

我试图读取长度为300和宽度为400的灰度图像的数据并将其加载到2D阵列。然后获取该数据并从中制作直方图。我没有收到任何编译错误，但我似乎无法阅读这些信息。谁能告诉我我做错了什么？谢谢。

Answer 1

你有几个问题;惊讶你没有得到段错误。

//This line creates an array of char *'s of size 300
T=(unsigned char**)malloc(300*sizeof(unsigned char*));
//this line is bad... the ; at the end means this is the entire loop.  This is equivalent to i = 400;
    for(i=0;i<400;i++);
//this is not part of the foor loop, so you do T[400] which is outside both the bounds you may have wanted (400) and the bounds you set(300)
    T[i]=(unsigned char*)malloc(400*sizeof(unsigned char*));
    while(fp)
    {
        //this will just keep overwriting the same line.
        fread(T[i],1,400,fp);

    }

这应该会更好一点：

int height = 300;
int width = 400;

T=(unsigned char**)malloc(height*sizeof(unsigned char*));
for(i=0;i<height;i++)
{
    if (feof(fp))
    {
       //handle error... could just malloc and memset to zero's
       break;
    }
    T[i]=(unsigned char*)malloc(width*sizeof(unsigned char*));
    fread(T[i],1,400,fp);
}

从文件中读取二进制数据

1 个答案: