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亲爱的 StackOverflow

我正在编写一个从另一个图像（imgInput）创建“棋盘图像”（imgOutput）的算法，就像这个例子一样。

它所做的是逐个检查图像的每个像素（500x500 像素），并将图片分成 2500 个 10x10 像素的盒子。我已经写了算法来计算平均 RGB 颜色，而不是绘制图像。这是代码：

    public class PixelMatrix
    {
        public int X;
        public int Y;
        public int R;
        public int G;
        public int B;
    }

    public class RGBMatrix
    {
        public int R;
        public int G;
        public int B;
    }

public Bitmap fncRasterize(Bitmap imgInput)
        {


            Bitmap imgOutput = new Bitmap(imgInput, 500, 500);
            imgOutput.Save("test.bmp");
            PixelMatrix[] arrWindows = new PixelMatrix[2500];
            RGBMatrix[] arrRGB = new RGBMatrix[100];

            Graphics gfx = Graphics.FromImage(imgOutput);


            int WindowCount = 1;
            int PixelCount = 1;

            int WindowX;
            int WindowY;

            int PixelX;
            int PixelY;

            int avrgR = 0;
            int avrgG = 0;
            int avrgB = 0;

            int tempcounter = 0;


            for (WindowY = 1; WindowY <= 50; WindowY++)
            {

                for (WindowX = 1; WindowX <= 50; WindowX++)
                {
                    PixelCount = 1;
                    avrgR = 0;

                    for (PixelY = 1;  PixelY <= 10; PixelY++)
                    {
                        for (PixelX = 1; PixelX <= 10; PixelX++)
                        {
                            MessageBox.Show("R:" + imgOutput.GetPixel(1, 1).R + " G:" + imgOutput.GetPixel(1, 1).G + " B:" +imgOutput.GetPixel(1, 1).B);

                            arrRGB[PixelCount].R = (int)imgOutput.GetPixel((WindowX * 10 - 10 + PixelX), (WindowY * 10 - 10 + PixelY)).R;
                            arrRGB[PixelCount].G = (int)imgOutput.GetPixel((WindowX * 10 - 10 + PixelX), (WindowY * 10 - 10 + PixelY)).G;
                            arrRGB[PixelCount].B = (int)imgOutput.GetPixel((WindowX * 10 - 10 + PixelX), (WindowY * 10 - 10 + PixelY)).B;

                            // This is just to test
                            tempcounter = +tempcounter;
                            lblProgress.Text = tempcounter.ToString();
                        }
                    }

                    for (int tempx = 1; tempx <= 100; tempx++)
                    {
                        avrgR = +arrRGB[tempx].R;
                        avrgG = +arrRGB[tempx].G;
                        avrgB = +arrRGB[tempx].B;
                    }
                    arrWindows[WindowCount].R = (avrgR / 100);
                    arrWindows[WindowCount].G = (avrgG / 100);
                    arrWindows[WindowCount].B = (avrgB / 100);

                    WindowCount = +1;

                }
            }




            return imgOutput;

        }

现在，当算法开始运行时，我在此行收到 NullReferenceException 错误：

 arrRGB[PixelCount].R = imgOutput.GetPixel(tempR.X, tempR.Y).R;
 arrRGB[PixelCount].G = imgOutput.GetPixel(tempG.X, tempG.Y).G;
 arrRGB[PixelCount].B = imgOutput.GetPixel(tempG.X, tempG.Y).B;

而它上面的行（Messagebox 语句）完美地返回了 RGB 值。有人可以向我解释为什么会这样吗？这真是令人沮丧。

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2 回答 2

1

您从未在 中创建RGBMatrix对象arrRGB，因此R G和B属性还不存在。这就是它的NullReferenceException来源。

于 2013-06-01T20:02:57.577 回答
0

您声明一个具有 100 个插槽的数组以包含 RGBMatrix 类型的元素。
但是在尝试访问实例的属性之前，您必须创建每个元素并将实例分配给正确的插槽。

for (PixelX = 1; PixelX <= 10; PixelX++)
{
    MessageBox.Show("R:" + imgOutput.GetPixel(1, 1).R + " G:" + imgOutput.GetPixel(1, 1).G + " B:" +imgOutput.GetPixel(1, 1).B);

    arrRGB[PixelCount] = new RBGMatrix();   // This create the instance

    arrRGB[PixelCount].R = (int).....
    arrRGB[PixelCount].G = (int)....
    arrRGB[PixelCount].B = (int)....

    // This is just to test
    tempcounter = +tempcounter;
    lblProgress.Text = tempcounter.ToString();
}

或其他方式

RGBMatrix mx = new new RBGMatrix();   
mx,R = = (int).....
....
arrRGB[PixelCount] = mx;
于 2013-06-01T20:07:38.157 回答