Question

我试图使用memcmp方法比较2个小图像块。我看到了这个答案What is the fastest way I can compare two equal-size bitmaps to determine whether they are identical? 我试图在我的项目中实现这个：

private void Form1_Load(object sender, EventArgs e)
{
    Bitmap prev, curr;

    prev = (Bitmap) Image.FromFile(@"C:\Users\Public\Desktop\b.png");



    curr = (Bitmap)Image.FromFile(@"C:\Users\Public\Desktop\b.png");
    MessageBox.Show(CompareMemCmp(prev, curr).ToString());
}

这是方法 -

[DllImport("msvcrt.dll")]
private static extern int memcmp(IntPtr b1, IntPtr b2, long count);

public static bool CompareMemCmp(Bitmap b1, Bitmap b2)
{
    if ((b1 == null) != (b2 == null)) return false;
    if (b1.Size != b2.Size) return false;

    var bd1 = b1.LockBits(new Rectangle(new Point(0, 0), b1.Size), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
    var bd2 = b2.LockBits(new Rectangle(new Point(0, 0), b2.Size), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

    try
    {
        IntPtr bd1scan0 = bd1.Scan0;
        IntPtr bd2scan0 = bd2.Scan0;

        int stride = bd1.Stride;
        int len = stride * b1.Height;

        return memcmp(bd1scan0, bd2scan0, len) == 0;
    }
    finally
    {
        b1.UnlockBits(bd1);
        b2.UnlockBits(bd2);
    }
}

我在调用memcmp函数

时遇到此错误

A call to PInvoke function 'WindowsFormsApplication1!WindowsFormsApplication1.Form1::memcmp' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

任何想法为什么会发生这种情况？我根据答案做了所有。

Answer 1

正确的签名是：

[DllImport("msvcrt.dll", CallingConvention=CallingConvention.Cdecl)]
static extern int memcmp(IntPtr b1, IntPtr b2, IntPtr count);

因为在C中，count是size_t，所以它可以是32位或64位，具体取决于程序是以32位还是64位运行。

然后使用它：

return memcmp(bd1scan0, bd2scan0, (IntPtr)len) == 0;

c＃memcmp image比较错误

1 个答案: