生成透明的PNG c＃
我有以下function来生成示例徽标。 我想要做的是返回透明的png或gif而不是白色背景。 我该怎么做？
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); }
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); }
看看你能用C＃做一个alpha透明的PNG吗？
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);