读取PPM格式图像

Question

P6

六百五十六五二

255

P6表示它是一个PPM映像。下两个字段是图像的宽度和高度。最后一个字段给出了最大像素值。在标题的末尾是一个\n，然后是二进制像素数据。图像是彩色的，因此有三个字节(红色、绿色、蓝色)。我的readPPM函数的目标是返回一维无符号字符数组中的像素数据，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格式映像写入一个空文件。我仍然不知道如何使这个程序工作，所以我不存储650的宽度和652的高度。一旦我真的能够读写文本文件，我就会担心这个问题。

更新:我已经成功地将标题(P6、650、652和255)存储在它们的正确变量中(我知道，因为我试图打印它们的值，它们得到了正确的结果)。我的输出如下所示。我想知道那些低于最大值的无稽之谈是什么。这些是二进制像素数据吗？如果是这样，那么我只需要编写我的writePPM函数。

输出： PSix: P6

宽度: 650

身高: 652

最高限额: 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

您没有将字符读入正确的位置。pixels已经是指向char的指针，所以您应该像传递给fscanf一样传递它。

fscanf(fr, "%c", pixels)

当然还有其他的问题，但是我这应该让你通过这个路障。