用C＃windows应用程序表单覆盖透明的图片框？

Question

我想放一张背景图片，在背景图片上方我想叠加一个透明的图片框，并尝试将第二个图片框放入：

pictureBox2.BackColor = Color.Transparent;

但它没有用。基本上，我想这样做：

Answer 1

Windows Forms中的透明度未按预期实施。具有透明背景实际上意味着控件使用其父级的背景。这意味着您需要使叠加控制成为原始图片框的子项：

PictureBox overlay = new PictureBox();

overlay.Dock = DockStyle.Fill;
overlay.BackColor = Color.FromArgb(128, Color.Blue);

pictureBox2.Controls.Add(overlay);

如果您希望叠加图片框包含透明图像，则需要实际更改图像：

PictureBox overlay = new PictureBox();
overlay.Dock = DockStyle.Fill;
overlay.BackColor = Color.Transparent;

Bitmap transparentImage = new Bitmap(overlayImage.Width, overlayImage.Height);
using (Graphics graphics = Graphics.FromImage(transparentImage))
{
    ColorMatrix matrix = new ColorMatrix();
    matrix.Matrix33 = 0.5f;

    ImageAttributes attributes = new ImageAttributes();
    attributes.SetColorMatrix(matrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);

    graphics.DrawImage(overlayImage, new Rectangle(0, 0, transparentImage.Width, transparentImage.Height), 0, 0, overlayImage.Width, overlayImage.Height, GraphicsUnit.Pixel, attributes);
}

overlay.Image = transparentImage;

pictureBox2.Controls.Add(overlay);