c#搜索图像中的像素时,for循环性能低下

Question

当我使用下面的代码时,如果找不到我在图像中搜索的图像,则在完成循环之前大约需要3-5秒.当这是搜索时,程序的其余部分暂停,我的计时器不同步,看起来程序冻结了几秒钟.图像不是很大,"printscreen"约为344x354,"Ok"约为15x7.我知道这是因为for循环,但有没有更好的方法来做到这一点,或者我可以以某种方式除了程序的其余部分之外,他的程序部分,所以程序不会冻结几秒钟.

// Ok is the image I am searching for.
// printscreen is the image I am searching in.

Bitmap Ok = new Bitmap(Properties.Resources.popupok1);
int Count = 0;
for (int x = 0; x < printscreen.Width; x++)
{
    for (int y = 0; y < printscreen.Height; y++)
    {
        Count = 0;
        if (printscreen.GetPixel(x, y) == Ok.GetPixel(0, 0) && 
            printscreen.GetPixel(x + 1, y) == Ok.GetPixel(1, 0))
        {
            for (int OkX = 0; OkX <= Ok.Width; OkX++)
            {
                for (int OkY = 0; OkY <= Ok.Height; OkY++)
                {
                    try
                    {
                        if (printscreen.GetPixel(x + OkX, y + OkY) != Ok.GetPixel(OkX, OkY))
                        {
                            OkX = Ok.Width;
                            OkY = Ok.Height;
                        }
                        else
                        {
                            Count += 1;
                        }
                        if (Count == 105)
                        {
                            X = x;
                            Y = y;
                            OkX = Ok.Width;
                            OkY = Ok.Height;
                            x = printscreen.Width - 1;
                            y = printscreen.Height - 1;
                            Console.Add("Ok button found.");
                            Console.Add("");
                            ConsoleUpdate();
                        }
                    }
                    catch { }
                }
            }
        }
    }
}

Answer 1

性能问题是由GetPixels/SetPixels引起的,这是访问.NET位图中数据的一种非常慢的方式.相反,我会研究Bitmap.LockBits方法来获取指向位图的指针并直接操作数据.它会快一个数量级.

请参阅MSDN:

以下代码示例演示如何使用PixelFormat,Height,Width和Scan0属性; LockBits和UnlockBits方法; 和ImageLockMode枚举.此示例旨在与Windows窗体一起使用.要运行此示例,请将其粘贴到表单中,并通过调用LockUnlockBitsExample方法处理表单的Paint事件,并将e作为PaintEventArgs传递.

private void LockUnlockBitsExample(PaintEventArgs e)
{

    // Create a new bitmap.
    Bitmap bmp = new Bitmap("c:\\fakePhoto.jpg");

    // Lock the bitmap's bits.  
    Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
    System.Drawing.Imaging.BitmapData bmpData = 
        bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite,
        bmp.PixelFormat);

    // Get the address of the first line.
           IntPtr ptr = bmpData.Scan0;

    // Declare an array to hold the bytes of the bitmap.
    // This code is specific to a bitmap with 24 bits per pixels.
    int bytes = bmp.Width * bmp.Height * 3;
    byte[] rgbValues = new byte[bytes];

    // Copy the RGB values into the array.
    System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);

    // Set every red value to 255.  
    for (int counter = 2; counter < rgbValues.Length; counter+=3)
        rgbValues[counter] = 255;

    // Copy the RGB values back to the bitmap
    System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes);

    // Unlock the bits.
    bmp.UnlockBits(bmpData);

    // Draw the modified image.
    e.Graphics.DrawImage(bmp, 0, 150);

}

如果你想要更快,而不是复制数组,操纵它并将其复制回来,你可以使用不安全的指针对位图进行操作.在这种情况下,内部部分将更改如下:

    // Lock the bitmap's bits.  
    Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
    System.Drawing.Imaging.BitmapData bmpData = 
        bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite,
        bmp.PixelFormat);

    // Get the address of the first line.
    IntPtr ptr = bmpData.Scan0;

    // Declare an array to hold the bytes of the bitmap.
    // This code is specific to a bitmap with 24 bits per pixels.
    int bytes = bmp.Width * bmp.Height * 3;
    unsafe
    {
        byte* rgbValues = (byte*)ptr;

        // Set every red value to 255.  
        for (int counter = 2; counter < bytes counter+=3)
            rgbValues[counter] = 255;
    } 

    // Unlock the bits.
    bmp.UnlockBits(bmpData);

请注意注意位图的PixelFormat.上面的例子假设它的每像素BGR为24位.实际上,许多位图都是BGRA(每像素32位),因此您需要按照每个像素的顺序修改蓝色,格力,红色,Alpha四个字节.