c - fread 导致数组变得不可读

Question

我正在尝试为 bmp 图像编写边缘检测方法，但在使用 fread 读取数据后，我无法访问保存像素 RGB 值的数组。

图像从 fread 读入的数组中写得很好，自然没有改变，所以我真的不确定这里发生了什么。我怀疑这与我分配数组的方式有关，但我不确定需要更改什么。非常感谢任何帮助。

struct fileHeader{
    unsigned short type;
    unsigned int size;
    unsigned short reservedOne, reservedTwo;
    unsigned int offset;
}Header;

struct infofileHeader{
    unsigned int size;
    int width, height;
    unsigned short planes;
    unsigned short bits;
    unsigned int compression;
    unsigned int imageSize;
    int xResolution, yResolution;
    unsigned int colors;
    unsigned int importantColors;
} infoHeader;

struct pixel{
    unsigned char Red, Green, Blue;
};

int main(int argc, char *argv[])
{
    int i;
    FILE* image = fopen(argv[1], "rb");
    FILE *testFile = fopen("out.bmp", "wb");

    fread(&Header.type, 2, 1, image);
    fread(&Header.size, 4, 1, image);
    fread(&Header.reservedOne, 2, 1, image);
    fread(&Header.reservedTwo, 2, 1, image);
    fread(&Header.offset, 4, 1, image);

    fread(&infoHeader.size, 4, 1, image);
    fread(&infoHeader.width, 4, 1, image);
    fread(&infoHeader.height, 4, 1, image);
    fread(&infoHeader.planes, 2, 1, image);
    fread(&infoHeader.bits, 2, 1, image);
    fread(&infoHeader.compression, 4, 1, image);
    fread(&infoHeader.imageSize, 4, 1, image);
    fread(&infoHeader.xResolution, 4, 1, image);
    fread(&infoHeader.yResolution, 4, 1, image);
    fread(&infoHeader.colors, 4, 1, image);
    fread(&infoHeader.importantColors, 4, 1, image);

    printf("%X\n", Header.type);
    printf("%d\n", Header.size);
    printf("%d\n", Header.offset);

    printf("Horizontal Resolution: %d\n", infoHeader.width);
    printf("Vertical Resolution: %d\n", infoHeader.height);
    printf("Total Resolution:Test %d\n", infoHeader.width * infoHeader.height);


    struct pixel **pixelArray = malloc(infoHeader.height * sizeof(pixelArray));
        if(pixelArray == NULL)printf("Could not allocate memory");

    for(i=0; i<infoHeader.height; i++){
        pixelArray[i] = (struct pixel*) malloc(infoHeader.width * sizeof(struct pixel));
            if(pixelArray[i] == NULL)printf("Could not allocate memory");
    }


    fread(pixelArray, sizeof(struct pixel), infoHeader.width*infoHeader.height, image);

    fclose(image);

    fwrite(&Header.type, 2, 1, testFile);
    fwrite(&Header.size, 4, 1, testFile);
    fwrite(&Header.reservedOne, 2, 1, testFile);
    fwrite(&Header.reservedTwo, 2, 1, testFile);
    fwrite(&Header.offset, 4, 1, testFile);

    fwrite(&infoHeader.size, 4, 1, testFile);
    fwrite(&infoHeader.width, 4, 1, testFile);
    fwrite(&infoHeader.height, 4, 1, testFile);
    fwrite(&infoHeader.planes, 2, 1, testFile);
    fwrite(&infoHeader.bits, 2, 1, testFile);
    fwrite(&infoHeader.compression, 4, 1, testFile);
    fwrite(&infoHeader.imageSize, 4, 1, testFile);
    fwrite(&infoHeader.xResolution, 4, 1, testFile);
    fwrite(&infoHeader.yResolution, 4, 1, testFile);
    fwrite(&infoHeader.colors, 4, 1, testFile);
    fwrite(&infoHeader.importantColors, 4, 1, testFile);

    fwrite(pixelArray, sizeof(struct pixel), 50000, testFile);

    /*for(i=0; i<infoHeader.height; i++){
        free(pixelArray[i]);
    }
    free(pixelArray);*/

    fclose(testFile);

    return 0;
}

Answer 1

...
fread(pixelArray, sizeof(struct pixel), infoHeader.width*infoHeader.height, image);
...

您不能以那种方式读取像素，因为您对每一行进行了不同的分配。

相反，您必须为每一行单独调用 fread。