生成透明PNG C＃ [英] Generate transparent PNG c#

问题描述

我有以下函数来产生一个样本的标识。我想要做的就是回到一个透明的PNG或GIF，而不是白色背景。
我该怎么办呢？

 私人位图CreateLogo（串子域）
 {
 
位图objBmpImage =新位图（1，1）; 
 INT intWidth = 0; 
 INT intHeight = 0; 
字体objFont =新的字体（宋体，13，System.Drawing.FontStyle.Bold，System.Drawing.GraphicsUnit.Pixel）; 
图形objGraphics = Graphics.FromImage（objBmpImage）; 
 intWidth =（int）的objGraphics.MeasureString（子域，objFont）.WIDTH; 
 intHeight =（int）的objGraphics.MeasureString（子域，objFont）.Height; 
 objBmpImage =新位图（objBmpImage，新的大小（intWidth，intHeight））; 
 objGraphics = Graphics.FromImage（objBmpImage）; 
 objGraphics.Clear（Color.White）; 
 objGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; 
 objGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias; 
 objGraphics.DrawString（子站点，objFont，新SolidBrush（Color.FromArgb（102，102，102）），0，0）; 
 objGraphics.Flush（）; 
回报（objBmpImage）; 
 
 
} 
  

下面是最终的结果。

  context.Response.ContentType =图像/ PNG 
使用（MemoryStream的memStream =新的MemoryStream（））
 {
 CreateLogo（_subdname）.Save（memStream，ImageFormat.Png）; 
 memStream.WriteTo（context.Response.OutputStream）; 
} 
  

功能

 私人位图CreateLogo（串子域）
 {
 
位图objBmpImage =新位图（1，1）; 
 INT intWidth = 0; 
 INT intHeight = 0; 
字体objFont =新的字体（宋体，13，System.Drawing.FontStyle.Bold，System.Drawing.GraphicsUnit.Pixel）; 
图形objGraphics = Graphics.FromImage（objBmpImage）; 
 intWidth =（int）的objGraphics.MeasureString（子域，objFont）.WIDTH; 
 intHeight =（int）的objGraphics.MeasureString（子域，objFont）.Height; 
 objBmpImage =新位图（objBmpImage，新的大小（intWidth，intHeight））; 
 objGraphics = Graphics.FromImage（objBmpImage）; 
 objGraphics.Clear（Color.Transparent）; 
 objGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias; 
 objGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias; 
 objGraphics.DrawString（子域名，objFont，新SolidBrush（Color.FromArgb（255，255，255）），0，0）; 
 objGraphics.Flush（）; 
回报（objBmpImage）; 
 
} 
  

解决方案

乘坐看看 http://stackoverflow.com/questions/388677/可以任您做安-α-透明PNG-与-C

I have below function to generate a sample logo. What I want to do is to return a transparent png or gif instead of white background. How can I do it?

private Bitmap CreateLogo(string subdomain)
{

    Bitmap objBmpImage = new Bitmap(1, 1);
    int intWidth = 0;
    int intHeight = 0;
    Font objFont = new Font("Arial", 13, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Pixel);
    Graphics objGraphics = Graphics.FromImage(objBmpImage);
    intWidth = (int)objGraphics.MeasureString(subdomain, objFont).Width;
    intHeight = (int)objGraphics.MeasureString(subdomain, objFont).Height;
    objBmpImage = new Bitmap(objBmpImage, new Size(intWidth, intHeight));
    objGraphics = Graphics.FromImage(objBmpImage);
    objGraphics.Clear(Color.White);
    objGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
    objGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
    objGraphics.DrawString(subdomain, objFont, new SolidBrush(Color.FromArgb(102, 102, 102)), 0, 0);
    objGraphics.Flush();
    return (objBmpImage);


}

here is the end result

context.Response.ContentType = "image/png";
            using (MemoryStream memStream = new MemoryStream()) 
            { 
                CreateLogo(_subdname).Save(memStream, ImageFormat.Png); 
                memStream.WriteTo(context.Response.OutputStream); 
            }

function

private Bitmap CreateLogo(string subdomain)
{

    Bitmap objBmpImage = new Bitmap(1, 1);
    int intWidth = 0;
    int intHeight = 0;
    Font objFont = new Font("Arial", 13, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Pixel);
    Graphics objGraphics = Graphics.FromImage(objBmpImage);
    intWidth = (int)objGraphics.MeasureString(subdomain, objFont).Width;
    intHeight = (int)objGraphics.MeasureString(subdomain, objFont).Height;
    objBmpImage = new Bitmap(objBmpImage, new Size(intWidth, intHeight));
    objGraphics = Graphics.FromImage(objBmpImage);
    objGraphics.Clear(Color.Transparent);
    objGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
    objGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
    objGraphics.DrawString(subdomain, objFont, new SolidBrush(Color.FromArgb(255, 255, 255)), 0, 0);
    objGraphics.Flush();
    return (objBmpImage);

}

解决方案

Take a look at http://stackoverflow.com/questions/388677/can-you-make-an-alpha-transparent-png-with-c

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