fwrite是如何工作的?

我试图用C语言编写一个程序,当我使用 fwrite()

// Go through each pixel of input bitmap
for (int y = 0; y < inWidth; y++)
{
    fread(pixel, sizeof(RGBTRIPLE), 1, inBMP);

    // Write each pixel to output bitmap (factor) times
    for (int z = 0; z < factor; z++)
    {
        fwrite(pixel, sizeof(RGBTRIPLE), 1, outBMP);
    }
}

一切正常:

但是当我使用 fwrite()

// Go through each pixel of input bitmap
for (int y = 0; y < inWidth; y++)
{
    fread(pixel, sizeof(RGBTRIPLE), 1, inBMP);

    // Write each pixel to output bitmap (factor) times
    fwrite(pixel, sizeof(RGBTRIPLE), factor, outBMP);
}

我明白了:

为什么会这样?