C＃picturebox透明背景似乎不起作用

Question

对于我的一个项目，我需要以透明背景显示图像。我制作了一些具有透明背景的 .png 图像（为了检查这一点，我在 Photoshop 中打开了它们）。现在我有一个扩展 PictureBox 的类：

class Foo : PictureBox
{
    public Foo(int argument)
        : base()
    {
        Console.WriteLine(argument);//different in the real application of course.
        //MyProject.Properties.Resources.TRANSPARENCYTEST.MakeTransparent(MyProject.Properties.Resources.TRANSPARENCYTEST.GetPixel(1,1)); //<-- also tried this
        this.Image = MyProject.Properties.Resources.TRANSPARENCYTEST;
        ((Bitmap)this.Image).MakeTransparent(((Bitmap)this.Image).GetPixel(1, 1));
        this.SizeMode = PictureBoxSizeMode.StretchImage;
        this.BackColor = System.Drawing.Color.Transparent;
    }
}

然而，这仅显示具有白色背景的图片框，我似乎无法使其与透明背景一起使用。

Answer 1

如果您想将图像覆盖在图像上（而不是图像覆盖在表单上），则可以使用以下方法：

overImage.Parent = backImage;
overImage.BackColor = Color.Transparent;
overImage.Location = thePointRelativeToTheBackImage;

其中 overImage 和 backImage 是带有 png 的 PictureBox（具有透明背景）。

这是因为，如前所述，图像的透明度是使用父容器的背景颜色渲染的。 PictureBoxes 没有“Parent”属性，因此您必须手动创建它（或者当然创建一个自定义控件）。

Answer 2

它可能工作得很好。您正在看到图片框控件背后的内容。这是哪种形式。谁的背景色可能是白色的。您可以设置表单的BackgroundImage 属性，以确保您应该通过图片框看到图像。像这样：

在图片框和上打一个洞 表单需要更大的武器，Form.TransparencyKey

Answer 3

CodeProject 网站上有一个出色的解决方案：

制作透明控件 - 无闪烁

本质上，技巧是重写paintbackground事件，以便循环遍历图片框下面的所有控件并重绘它们。其功能是：-

protected override void OnPaintBackground(PaintEventArgs e)
       // Paint background with underlying graphics from other controls
   {
       base.OnPaintBackground(e);
       Graphics g = e.Graphics;

       if (Parent != null)
       {
           // Take each control in turn
           int index = Parent.Controls.GetChildIndex(this);
           for (int i = Parent.Controls.Count - 1; i > index; i--)
           {
               Control c = Parent.Controls[i];

               // Check it's visible and overlaps this control
               if (c.Bounds.IntersectsWith(Bounds) && c.Visible)
               {
                   // Load appearance of underlying control and redraw it on this background
                   Bitmap bmp = new Bitmap(c.Width, c.Height, g);
                   c.DrawToBitmap(bmp, c.ClientRectangle);
                   g.TranslateTransform(c.Left - Left, c.Top - Top);
                   g.DrawImageUnscaled(bmp, Point.Empty);
                   g.TranslateTransform(Left - c.Left, Top - c.Top);
                   bmp.Dispose();
               }
           }
       }
   }

Answer 4

我知道您的问题是在 C# 中建立的，但由于相似，&为了便于从 VB.NET 进行转换，我将添加一个完整的 VB 版本，该版本还允许在移动控件时更新控件的背景。

您已经有了答案，但这适用于通过搜索引擎找到这篇文章的其他人，&想要一个 VB 版本，或者只是想找到一个完整的可转换示例（如果他们还需要 C# 版本）。

创建一个新的自定义控件类，&将以下内容粘贴到其中...覆盖默认类内容：

自定义控件类：

Public Class TransparentPictureBox
    Private WithEvents refresher As Timer
    Private _image As Image = Nothing

    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        refresher = New Timer()
        'refresher.Tick += New EventHandler(AddressOf Me.TimerOnTick)
        refresher.Interval = 50
        refresher.Start()

    End Sub

    Protected Overrides ReadOnly Property CreateParams() As CreateParams
        Get
            Dim cp As CreateParams = MyBase.CreateParams
            cp.ExStyle = cp.ExStyle Or &H20
            Return cp
        End Get
    End Property

    Protected Overrides Sub OnMove(ByVal e As EventArgs)
        MyBase.OnMove(e)
        MyBase.RecreateHandle()
    End Sub

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        MyBase.OnPaint(e)

        'Add your custom paint code here
        If _image IsNot Nothing Then
            e.Graphics.DrawImage(_image, CInt(Width / 2) - CInt(_image.Width / 2), CInt(Height / 2) - CInt(_image.Height / 2))
        End If
    End Sub


    Protected Overrides Sub OnPaintBackground(ByVal e As System.Windows.Forms.PaintEventArgs)
        ' Paint background with underlying graphics from other controls
        MyBase.OnPaintBackground(e)
        Dim g As Graphics = e.Graphics

        If Parent IsNot Nothing Then
            ' Take each control in turn
            Dim index As Integer = Parent.Controls.GetChildIndex(Me)
            For i As Integer = Parent.Controls.Count - 1 To index + 1 Step -1
                Dim c As Control = Parent.Controls(i)

                ' Check it's visible and overlaps this control
                If c.Bounds.IntersectsWith(Bounds) AndAlso c.Visible Then
                    ' Load appearance of underlying control and redraw it on this background
                    Dim bmp As New Bitmap(c.Width, c.Height, g)
                    c.DrawToBitmap(bmp, c.ClientRectangle)
                    g.TranslateTransform(c.Left - Left, c.Top - Top)
                    g.DrawImageUnscaled(bmp, Point.Empty)
                    g.TranslateTransform(Left - c.Left, Top - c.Top)
                    bmp.Dispose()
                End If
            Next
        End If
    End Sub

    Public Property Image() As Image
        Get
            Return _image
        End Get
        Set(value As Image)
            _image = value
            MyBase.RecreateHandle()
        End Set
    End Property

    Private Sub refresher_Tick(sender As Object, e As System.EventArgs) Handles refresher.Tick
        MyBase.RecreateHandle()
        refresher.Stop()
    End Sub
End Class

...保存类，然后清理您的项目，&再次构建。新控件应显示为新工具项。找到它，&将其拖到您的表单中。

不过，我在使用此控件时遇到了问题...当我尝试加载动画“正在加载”.gif 图像时，就会发生这种情况。

图像没有动画，&当您隐藏控件然后尝试再次显示它时也会出现显示问题。

解决这些问题，&您将拥有一个完美的自定义控制类。 :)

编辑：

我不知道以下内容是否适用于 C# 的 IDE，但这是我的转换尝试：

using Microsoft.VisualBasic;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
public class TransparentPictureBox
{
    private Timer withEventsField_refresher;
    private Timer refresher {
        get { return withEventsField_refresher; }
        set {
            if (withEventsField_refresher != null) {
                withEventsField_refresher.Tick -= refresher_Tick;
            }
            withEventsField_refresher = value;
            if (withEventsField_refresher != null) {
                withEventsField_refresher.Tick += refresher_Tick;
            }
        }
    }

    private Image _image = null;

    public TransparentPictureBox()
    {
        // This call is required by the designer.
        InitializeComponent();

        // Add any initialization after the InitializeComponent() call.
        refresher = new Timer();
        //refresher.Tick += New EventHandler(AddressOf Me.TimerOnTick)
        refresher.Interval = 50;
        refresher.Start();

    }

    protected override CreateParams CreateParams {
        get {
            CreateParams cp = base.CreateParams;
            cp.ExStyle = cp.ExStyle | 0x20;
            return cp;
        }
    }

    protected override void OnMove(EventArgs e)
    {
        base.OnMove(e);
        base.RecreateHandle();
    }

    protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
    {
        base.OnPaint(e);

        //Add your custom paint code here
        if (_image != null) {
            e.Graphics.DrawImage(_image, Convert.ToInt32(Width / 2) - Convert.ToInt32(_image.Width / 2), Convert.ToInt32(Height / 2) - Convert.ToInt32(_image.Height / 2));
        }
    }


    protected override void OnPaintBackground(System.Windows.Forms.PaintEventArgs e)
    {
        // Paint background with underlying graphics from other controls
        base.OnPaintBackground(e);
        Graphics g = e.Graphics;

        if (Parent != null) {
            // Take each control in turn
            int index = Parent.Controls.GetChildIndex(this);
            for (int i = Parent.Controls.Count - 1; i >= index + 1; i += -1) {
                Control c = Parent.Controls(i);

                // Check it's visible and overlaps this control
                if (c.Bounds.IntersectsWith(Bounds) && c.Visible) {
                    // Load appearance of underlying control and redraw it on this background
                    Bitmap bmp = new Bitmap(c.Width, c.Height, g);
                    c.DrawToBitmap(bmp, c.ClientRectangle);
                    g.TranslateTransform(c.Left - Left, c.Top - Top);
                    g.DrawImageUnscaled(bmp, Point.Empty);
                    g.TranslateTransform(Left - c.Left, Top - c.Top);
                    bmp.Dispose();
                }
            }
        }
    }

    public Image Image {
        get { return _image; }
        set {
            _image = value;
            base.RecreateHandle();
        }
    }

    private void refresher_Tick(object sender, System.EventArgs e)
    {
        base.RecreateHandle();
        refresher.Stop();
    }
}

尝试一下，&我想你自己看看：P

PS：我不是专家，所以预计 C# 和 C# 中都会出现各种错误。 VB.NET 版本。哈哈

Answer 5

如果你在图片框中显示透明的png，它会自动考虑透明度，所以你不需要设置透明颜色

Answer 6

上面的答案似乎解决了你的问题。您确实看到了图片框控件背后的内容 - 表单本身的 backColor 为白色。我在这里创建了一个简单的函数，首先将字节类型（数组）的图像转换为位图，然后将特定颜色（来自位图图片）设置为透明。你不妨使用一些东西：

 使用系统；
   使用系统绘图；
   使用系统.绘图.成像；
   使用 System.Windows.Forms；

    public void LogoDrawTransparent(PaintEventArgs e)
    {
        // Create a Bitmap object from an image file.
        Image myImg;
        Bitmap myBitmap;

        try
        {
            myImg = cls_convertImagesByte.GetImageFromByte(newImg);
            myBitmap = new Bitmap(myImg); // @"C:\Temp\imgSwacaa.jpg");  

            // Get the color of a background pixel.
            Color backColor = myBitmap.GetPixel(0, 0); // GetPixel(1, 1); 
            Color backColorGray = Color.Gray;
            Color backColorGrayLight = Color.LightGray;
            Color backColorWhiteSmoke = Color.WhiteSmoke;
            Color backColorWhite = Color.White;
            Color backColorWheat = Color.Wheat;

            // Make backColor transparent for myBitmap.
            myBitmap.MakeTransparent(backColor);
                    // OPTIONALLY, you may make any other "suspicious" back color transparent (usually gray, light gray or whitesmoke)
            myBitmap.MakeTransparent(backColorGray);
            myBitmap.MakeTransparent(backColorGrayLight);
            myBitmap.MakeTransparent(backColorWhiteSmoke);

            // Draw myBitmap to the screen.
            e.Graphics.DrawImage(myBitmap, 0, 0, pictureBox1.Width, pictureBox1.Height); //myBitmap.Width, myBitmap.Height);
        }
        catch
        {
            try { pictureBox1.Image = cls_convertImagesByte.GetImageFromByte(newImg); }
            catch { } //must do something
        }
    }

您可以在 pictureBox 的 Paint 上触发此函数。
这是我的类在上面的函数中引用：

    class cls_convertImagesByte
{

    public static Image GetImageFromByte(byte[] byteArrayIn)
    {
        MemoryStream ms = new MemoryStream(byteArrayIn);
        Image returnImage = Image.FromStream(ms);
        return returnImage;
    }

    public static byte[] GetByteArrayFromImage(System.Drawing.Image imageIn)
    {
        MemoryStream ms = new MemoryStream();
        imageIn.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
        return ms.ToArray();
    }
}

谢谢。查格伯特