更改位图图像的不透明度 [英] Changing the Opacity of a Bitmap image

问题描述

我有一个带有图像的表单.我正在使用滑块来更改图像的不透明度.因此，在滑块的ValueChanged"事件中，我调用以下方法来更改不透明度.

I have a form which has a image. I am using a slider to change the opacity of the image. So in the "ValueChanged" event of the slider I am calling the following method to change the opacity.

//Setting the opacity of the image
public static Image SetImgOpacity(Image imgPic, float imgOpac)
{   
     Bitmap bmpPic = new Bitmap(imgPic.Width, imgPic.Height);
     Graphics gfxPic = Graphics.FromImage(bmpPic);

     ColorMatrix cmxPic = new ColorMatrix();   
     cmxPic.Matrix33 = imgOpac;   
     ImageAttributes iaPic = new ImageAttributes();   
     iaPic.SetColorMatrix(cmxPic, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);  
     gfxPic.DrawImage(imgPic, new Rectangle(0, 0, bmpPic.Width, bmpPic.Height), 0, 0, imgPic.Width, imgPic.Height, GraphicsUnit.Pixel, iaPic);  
     gfxPic.Dispose();            

     return bmpPic;  
}

返回的Image设置为原始图像.

The returned Image is set to the original image.

我的问题是图像的不透明度没有改变...如果有任何错误请指出...谢谢...

My problem is that the opacity of the image is not changing... If there is any error please be kind enough to point out.. Thnx...

推荐答案

试试 CodeProject 中的这个 - 在 C# 中更改图像的不透明度:

Try this one from CodeProject - Change Opacity of Image in C#:

/// <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;  
    }  
} 

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