如何从图片框中获取特定像素的颜色? [英] How do I get the color of a specific pixel from a picture box?

问题描述

我的一个程序中有一个图片框，可以很好地显示我的图像.显示的内容包括选定的背景色"和一些使用画笔填充的矩形和一些使用钢笔填充的线条.我没有导入的图像.我需要检索图片框上指定像素的颜色值.我尝试了以下方法:

I have a picture box in one of my programs which displays my images just fine. What's displayed consists of a chosen "BackColor" and some filled rectangles using a brush and some lines using a pen. I have no imported images. I need to retrieve the color value of a specified pixel on the picture box. I've tried the following:

Bitmap b = new Bitmap(pictureBox1.Image);          
                Color colour = b.GetPixel(X,Y)

但是pictureBox1.Image 总是返回null..Image 是否仅适用于导入的图像?如果不是，我怎样才能让它发挥作用?有没有其他选择?

But pictureBox1.Image always returns null. Does .Image only work with imported images? If not how can I get this to work? Are there any alternatives?

推荐答案

是的，你可以，但应该你吗?

这是您的代码需要的更改:

Here is the change your code needs:

Bitmap b = new Bitmap(pictureBox1.ClientSize.Width, pictureBox1.Height);
pictureBox1.DrawToBitmap(b, pictureBox1.ClientRectangle);
Color colour = b.GetPixel(X, Y);
b.Dispose();

但是如果你想用它做真正的工作，真的没有办法给 PictureBox 一个真正的 Image 来处理它，这意味着如果你想使用它它的可能性，例如它的 SizeMode.

But there is really no way around giving the PictureBox a real Image to work with somewhere if you want to do real work with it, meaning if you want to use its possibilities e.g. its SizeMode.

简单地在其背景上绘图是不一样的.这是分配真实位图的最少代码:

Simply drawing on its background is just not the same. Here is a minimal code to get a real Bitmap assigned:

public Form1()
{
   InitializeComponent();
   pictureBox1.Image = new Bitmap(pictureBox1.ClientSize.Width, 
                                  pictureBox1.ClientSize.Height); 
   using (Graphics graphics = Graphics.FromImage(pictureBox1.Image))
   { 
     graphics.FillRectangle(Brushes.CadetBlue, 0, 0, 99, 99);
     graphics.FillRectangle(Brushes.Beige, 66, 55, 66, 66);
     graphics.FillRectangle(Brushes.Orange, 33, 44, 55, 66);
   }  
}

然而，如果你真的不想分配一个图像，你可以让 PictureBox 将自己绘制到一个真正的 Bitmap 上.请注意，您必须在 Paint 事件中绘制矩形等以使其正常工作！(实际上，您也必须出于其他原因使用 Paint 事件！)

However if you really don't want to assign an Image you can make the PictureBox draw itself onto a real Bitmap. Note that you must draw the Rectangles etc in the Paint event for this to work! (Actually you must use the Paint event for other reasons as well!)

现在您可以测试任何一种方式，例如使用标签和鼠标:

Now you can test either way e.g. with a Label and your mouse:

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    if (pictureBox1.Image != null)
    {   // the 'real thing':
        Bitmap bmp = new Bitmap(pictureBox1.Image);
        Color colour = bmp.GetPixel(e.X, e.Y);
        label1.Text = colour.ToString();
        bmp.Dispose();
    }
    else
    {   // just the background:
        Bitmap bmp = new Bitmap(pictureBox1.ClientSize.Width, pictureBox1.Height);
        pictureBox1.DrawToBitmap(bmp, pictureBox1.ClientRectangle);
        Color colour = bmp.GetPixel(e.X, e.Y);
        label1.Text += "ARGB :" + colour.ToString();
        bmp.Dispose();
    }
}

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    e.Graphics.FillRectangle(Brushes.DarkCyan, 0, 0, 99, 99);
    e.Graphics.FillRectangle(Brushes.DarkKhaki, 66, 55, 66, 66);
    e.Graphics.FillRectangle(Brushes.Wheat, 33, 44, 55, 66);
}

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