[英]Generate transparent PNG c#
我有以下功能来生成示例徽标。 我想要做的是返回一个透明的 png 或 gif 而不是白色背景。
我怎样才能做到这一点?
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);
}
这是最终结果:
context.Response.ContentType = "image/png";
using (MemoryStream memStream = new MemoryStream())
{
CreateLogo(_subdname).Save(memStream, ImageFormat.Png);
memStream.WriteTo(context.Response.OutputStream);
}
在CreateLogo
函数中:
objGraphics.Clear(Color.White)
改为objGraphics.Clear(Color.Transparent)
new SolidBrush(Color.FromArgb(102, 102, 102))
改为new SolidBrush(Color.FromArgb(255, 255, 255))
你可以这样做:
Bitmap bmp = new Bitmap(300, 300);
Graphics g = Graphics.FromImage(bmp);
g.Clear(Color.Transparent);
g.FillRectangle(Brushes.Red, 100, 100, 100, 100);
g.Flush();
bmp.Save("test.png", System.Drawing.Imaging.ImageFormat.Png);
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