我不熟悉ImageAttributes
方法,但是您应该能够简单遍历图像的所有像素并修改像素颜色的alpha分量。

更改位图图像的不透明度

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0

从CodeProject尝试这一操作- 在C#中更改图像的不透明度 :
/// <summary>
/// method for changing the opacity of an image
/// </summary>
/// <param name="image">image to set opacity on</param>
/// <param name="opacity">percentage of opacity</param>
/// <returns></returns>
public Image SetImageOpacity(Image image, float opacity)
{
try
{
//create a Bitmap the size of the image provided
Bitmap bmp = new Bitmap(image.Width, image.Height);
//create a graphics object from the image
using (Graphics gfx = Graphics.FromImage(bmp)) {
//create a color matrix object
ColorMatrix matrix = new ColorMatrix();
//set the opacity
matrix.Matrix33 = opacity;
//create image attributes
ImageAttributes attributes = new ImageAttributes();
//set the color(opacity) of the image
attributes.SetColorMatrix(matrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
//now draw the image
gfx.DrawImage(image, new Rectangle(0, 0, bmp.Width, bmp.Height), 0, 0, image.Width, image.Height, GraphicsUnit.Pixel, attributes);
}
return bmp;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return null;
}
}
0

您循环播放像素并仅播放Alpha通道。如果使用Bitmap.LockBits执行此操作,则实际上将非常快。
private const int bytesPerPixel = 4;
/// <summary>
/// Change the opacity of an image
/// </summary>
/// <param name="originalImage">The original image</param>
/// <param name="opacity">Opacity, where 1.0 is no opacity, 0.0 is full transparency</param>
/// <returns>The changed image</returns>
public static Image ChangeImageOpacity(Image originalImage, double opacity)
{
if ((originalImage.PixelFormat & PixelFormat.Indexed) == PixelFormat.Indexed)
{
// Cannot modify an image with indexed colors
return originalImage;
}
Bitmap bmp = (Bitmap)originalImage.Clone();
// Specify a pixel format.
PixelFormat pxf = PixelFormat.Format32bppArgb;
// Lock the bitmap's bits.
Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
BitmapData bmpData = bmp.LockBits(rect, ImageLockMode.ReadWrite, pxf);
// 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 32 bits per pixels
// (32 bits = 4 bytes, 3 for RGB and 1 byte for alpha).
int numBytes = bmp.Width * bmp.Height * bytesPerPixel;
byte[] argbValues = new byte[numBytes];
// Copy the ARGB values into the array.
System.Runtime.InteropServices.Marshal.Copy(ptr, argbValues, 0, numBytes);
// Manipulate the bitmap, such as changing the
// RGB values for all pixels in the the bitmap.
for (int counter = 0; counter < argbValues.Length; counter += bytesPerPixel)
{
// argbValues is in format BGRA (Blue, Green, Red, Alpha)
// If 100% transparent, skip pixel
if (argbValues[counter + bytesPerPixel - 1] == 0)
continue;
int pos = 0;
pos++; // B value
pos++; // G value
pos++; // R value
argbValues[counter + pos] = (byte) (argbValues[counter + pos] * opacity);
}
// Copy the ARGB values back to the bitmap
System.Runtime.InteropServices.Marshal.Copy(argbValues, 0, ptr, numBytes);
// Unlock the bits.
bmp.UnlockBits(bmpData);
return bmp;
}
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我有一个带有图像的表格。我正在使用滑块更改图像的不透明度。因此,在滑块的“ ValueChanged”事件中,我正在调用以下方法来更改不透明度。
返回的图像设置为原始图像。
我的问题是图像的不透明度没有改变...如果有任何错误,请友好地指出.. Thnx ...