读PPM格式图像

Question

P6

P6表示它是一个PPM图像。接下来的两个字段是图像的宽度和高度。最后一个字段给出最大像素值。在头部的末尾是\ n，然后是二进制像素数据。图像是彩色的，所以有三个字节（红色，绿色，蓝色）。 readPPM函数的目标是将像素数据返回到无符号字符的一维数组中，再加上图像的宽度和高度。我的writePPM函数（我还没有为这个函数做任何事情）的目标是从我的readPPM函数返回的给定信息中将PPM格式图像写入一个空文件。我仍然不确定如何使这个程序工作，所以我不存储650宽度和652高度。一旦我真的可以读写文本文件，我会担心这一点。 （我知道，因为我试图打印他们的值，他们出来右）成功地存储头（P6,650,652和255））在他们的右变量。我的输出如下所示。我想知道那些低于最大值的无意义字符是什么。那些是二进制像素数据吗？如果是这样，那么我只需要写我的writePPM函数。

输出： PSix：P6

宽度：650

高度：652

最大：？？？？？？255

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main.cc

int main() { 

char fileName[50] = "binary_pixels.txt"; 
int width = 0; // width of the image 
int height = 0; // heigt of the image 
int size = 128; // size of the array 

// read the PPM file and store its contents inside an array and return 
// the pointer to that array to pixelArray 
unsigned char* pixelArray[size] = readPPM(fileName, &width, &height); 

// print the contents of the array 
for (int i = 0; i < 128; i++) { 
    printf("%s\n", pixelArray[i]); 
} // end of for loop 

} // end of main 

readPPM.cc

unsigned char readPPM(const char* fileName, char* pSix, int* width,   
int* height, int* maximum) { 

// open the file to read just the header reading 
FILE* fr = fopen(fileName, "r"); 

// formatted read of header 
fscanf(fr, "%s", pSix); 

// check to see if it's a PPM image file 
if (strncmp(pSix, "p6" , 10) != 0) { 
    printf("They are not the same\n"); 
} else { 
    printf("They are the same\n"); 
} 

// read the rest of header 
fscanf(fr, "%d\n %d\n", width, height); 

fscanf(fr, "%d\n", maximum); 

// check to see if they were stored properly 
printf("PSix: %s\n", pSix); 
printf("Width: %d\n", *width); 
printf("Height: %d\n", *height); 
printf("maximum: %d\n", *maximum); 

// allocate array for pixels 
unsigned char* pixels = new unsigned char[width * height]; 

// unformatted read of binary pixel data 
while (fread(pixels, sizeof(pixel), 128, fr)) { 
    printf("%s", pixels); 
} // end of for loop 

// close file 
fclose(fr); 

// return the array 
return pixels; 

} // end of readPPM 

Answer 1

//struct to hold a pixel. 
struct rgb 
{ 
    char r; 
    char g; 
    char b; 
}; 

//struct to hold the image and its info. 
struct image 
{ 
    char p; 
    int format; 
    int width; 
    int height; 
    int intensity; 
    //struct rgb **rgb; 
    unsigned char *pixels; 
}; 

int main(void) 
{ 
    struct image m; 
    FILE *fp = //fopen(...); 

    fscanf(fp, "%c%d\n", &m.p, &m.format); 

    fscanf(fp, "%d %d\n", &m.width, &m.height); 

    fscanf(fp, "%d\n", &m.intensity); 

    printf("%c%d\n", m.p, m.format); 
    printf("%d %d\n", m.width, m.height); 
    printf("%d\n", m.intensity); 

    //allocate array to hold the pixels 
    m.pixel = (unsigned char*)malloc(m.width*m.heigth*3*sizeof(unsigned char)); 

    //read pixels into m.pixel 
    return 0; 
} 

Answer 2

您是不读取字符到正确的位置。pixels已经是一个指向char如此的，你应该把它当作是fscanf：

fscanf(fr, "%c", pixels) 

当然还有其他的问题，但我这应该让你通过这条路块。