C#生成透明背景图片的方法
/// <summary>
/// Returns a transparent background GIF image from the specified Bitmap.
/// </summary>
/// <param name="bitmap">The Bitmap to make transparent.</param>
/// <param name="color">The Color to make transparent.</param>
/// <returns>New Bitmap containing a transparent background gif.</returns>
public Bitmap MakeTransparentGif(Bitmap bitmap, Color color)
{
byte R = color.R;
byte G = color.G;
byte B = color.B;
MemoryStream fin = new MemoryStream();
bitmap.Save(fin, System.Drawing.Imaging.ImageFormat.Gif);
MemoryStream fout = new MemoryStream((int)fin.Length);
int count = 0;
byte[] buf = new byte[256];
byte transparentIdx = 0;
fin.Seek(0, SeekOrigin.Begin);
//header
count = fin.Read(buf, 0, 13);
if ((buf[0] != 71) || (buf[1] != 73) || (buf[2] != 70)) return null; //GIF
fout.Write(buf, 0, 13);
int i = 0;
if ((buf[10] & 0x80) > 0)
{
i = 1 << ((buf[10] & 7) + 1) == 256 ? 256 : 0;
}
for (; i != 0; i--)
{
fin.Read(buf, 0, 3);
if ((buf[0] == R) && (buf[1] == G) && (buf[2] == B))
{
transparentIdx = (byte)(256 - i);
}
fout.Write(buf, 0, 3);
}
bool gcePresent = false;
while (true)
{
fin.Read(buf, 0, 1);
fout.Write(buf, 0, 1);
if (buf[0] != 0x21) break;
fin.Read(buf, 0, 1);
fout.Write(buf, 0, 1);
gcePresent = (buf[0] == 0xf9);
while (true)
{
fin.Read(buf, 0, 1);
fout.Write(buf, 0, 1);
if (buf[0] == 0) break;
count = buf[0];
if (fin.Read(buf, 0, count) != count) return null;
if (gcePresent)
{
if (count == 4)
{
buf[0] |= 0x01;
buf[3] = transparentIdx;
}
}
fout.Write(buf, 0, count);
}
}
while (count > 0)
{
count = fin.Read(buf, 0, 1);
fout.Write(buf, 0, 1);
}
fin.Close();
fout.Flush();
return new Bitmap(fout);
}
public void doTextImage(string FamilyName, string fontStyle, string FontWeight, string Text, int intFontSize, string FontColor, int Width, int Height, string TextAlign)
{
Bitmap bitmap = null;
bitmap = new Bitmap(Width, Height);
Graphics g = Graphics.FromImage(bitmap);
//设置画笔
Color color = ColorTranslator.FromHtml(FontColor);
Brush brush = new SolidBrush(color);
//设置字体
FontStyle ftStyle = new FontStyle();
if (fontStyle.ToLower() == "italic" && FontWeight.ToLower() == "bold")
{
ftStyle = FontStyle.Italic | FontStyle.Bold;
}
else if (fontStyle.ToLower() == "italic" && FontWeight.ToLower() != "bold")
{
ftStyle = FontStyle.Italic;
}
else if (fontStyle.ToLower() != "italic" && FontWeight.ToLower() == "bold")
{
ftStyle = FontStyle.Bold;
}
else
{
ftStyle = FontStyle.Regular;
}
Font font;
font = new Font(FamilyName, intFontSize, ftStyle, GraphicsUnit.Pixel);
//设置绘图区域
RectangleF rect = new RectangleF(0, 0, Width, Height);
//设置文本绘制格式
StringFormat stringFormat = new StringFormat();
if (TextAlign.ToLower() == "center")
{
stringFormat.LineAlignment = StringAlignment.Center;
}
else if (TextAlign.ToLower() == "right")
{
stringFormat.LineAlignment = StringAlignment.Far;
}
else
{
stringFormat.LineAlignment = StringAlignment.Near;
}
//设置绘图质量
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.SmoothingMode = SmoothingMode.HighQuality;
g.PixelOffsetMode = PixelOffsetMode.HighQuality;
g.CompositingMode = CompositingMode.SourceOver;
g.CompositingQuality = CompositingQuality.HighQuality;
g.TextRenderingHint = TextRenderingHint.AntiAliasGridFit;
g.PageUnit = GraphicsUnit.Pixel;
//设置透明背景
g.Clear(Color.Transparent);
//绘制字符串
g.DrawString(Text, font, brush, rect, stringFormat);
//取浏览器版本，IE6显示透明gif，其它则显示透明png
if (GetBrowsetype() == "IE" && GetBrowseVersion() == "6.0")
{
bitmap = MakeTransparentGif(bitmap, Color.Black);
System.IO.MemoryStream ms = new System.IO.MemoryStream();
bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
byte[] bytes = ms.GetBuffer();
g.Dispose();
bitmap.Dispose();
Response.Clear();
Response.ContentType = "image/Gif";
Response.BinaryWrite(bytes);
}
else
{
System.IO.MemoryStream ms = new System.IO.MemoryStream();
bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
byte[] bytes = ms.GetBuffer();
g.Dispose();
bitmap.Dispose();
Response.Clear();
Response.ContentType = "image/Png";
Response.BinaryWrite(bytes);
}
}
public static string GetBrowseVersion()
{
System.Web.HttpBrowserCapabilities browser = System.Web.HttpContext.Current.Request.Browser;
return browser.Version;
}
public static string GetBrowsetype()
{
System.Web.HttpBrowserCapabilities browser = System.Web.HttpContext.Current.Request.Browser;
return browser.Browser;
}
