/// <summary>
/// 圖片疊加
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button1_Click(object sender, EventArgs e)
{
string path = Server.MapPath(@"image/20160102.png");
System.Drawing.Image imgSrc = System.Drawing.Image.FromFile(path);
System.Drawing.Image imgWarter = System.Drawing.Image.FromFile(Server.MapPath(@"Image/bear.png"));
using (Graphics g = Graphics.FromImage(imgSrc))
{
g.DrawImage(imgWarter, new Rectangle(imgSrc.Width - imgWarter.Width, imgSrc.Height - imgWarter.Height, imgWarter.Width, imgWarter.Height), 0, 0, imgWarter.Width, imgWarter.Height, GraphicsUnit.Pixel);
}

string newpath = Server.MapPath(@"Image/WaterMark.bmp");
imgSrc.Save(newpath, System.Drawing.Imaging.ImageFormat.Jpeg);
this.image_Water.ImageUrl = @"~/Image/WaterMark.bmp";
}

/// <summary>
/// 圖片上嵌入文字
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button2_Click(object sender, EventArgs e)
{
string path = Server.MapPath(@"image/20160102.png");
System.Drawing.Image imgSrc = System.Drawing.Image.FromFile(path);

using (Graphics g = Graphics.FromImage(imgSrc))
{
g.DrawImage(imgSrc, 0, 0, imgSrc.Width, imgSrc.Height);
using (Font f = new Font("宋體", 20))
{
using (Brush b = new SolidBrush(Color.Red))
{
string addText = "我的地盤我做主"; g.DrawString(addText, f, b, 100, 20);
}
}
}
string fontpath = Server.MapPath(@"image/FontMark.bmp");
imgSrc.Save(fontpath, System.Drawing.Imaging.ImageFormat.Bmp);
this.image_Water.ImageUrl = @"~/image/FontMark.bmp";

}

////////////////////////////////////////以下為文字生成圖片//////////////////////////////////////////////////////////

/// <summary>
/// 把文字轉換才Bitmap
/// </summary>
/// <param name="text"></param>
/// <param name="font"></param>
/// <param name="rect">用於輸出的矩形，文字在這個矩形內顯示，為空時自動計算</param>
/// <param name="fontcolor">字體顏色</param>
/// <param name="backColor">背景顏色</param>
/// <returns></returns>
private Bitmap TextToBitmap(string text, Font font, Rectangle rect, Color fontcolor, Color backColor)
{
Graphics g;
Bitmap bmp;
StringFormat format = new StringFormat(StringFormatFlags.NoClip);
if (rect == Rectangle.Empty)
{
bmp = new Bitmap(1, 1);
g = Graphics.FromImage(bmp);
//計算繪制文字所需的區域大小（根據寬度計算長度），重新創建矩形區域繪圖
SizeF sizef = g.MeasureString(text, font, PointF.Empty, format);

int width = (int)(sizef.Width + 1);
int height = (int)(sizef.Height + 1);
rect = new Rectangle(0, 0, width, height);
bmp.Dispose();

bmp = new Bitmap(width, height);
}
else
{
bmp = new Bitmap(rect.Width, rect.Height);
}

g = Graphics.FromImage(bmp);

//使用ClearType字體功能
g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;
g.FillRectangle(new SolidBrush(backColor), rect);
g.DrawString(text, font, Brushes.Black, rect, format);
return bmp;
}

protected void Button1_Click(object sender, EventArgs e)
{
string str = @"開始時間:2016-1-1" + "\r\n" + "結束時間:2017-1-1"+"\r\n"+ "沙塵天氣等級:2"+"\r\n" + "PM10日均濃度最大值:2ug/m3"+"\r\n" + "影響範圍:濟南，青島";
//得到Bitmap(傳入Rectangle.Empty自動計算寬高)
Bitmap bmp = TextToBitmap(str, new Font("Arial", 16), Rectangle.Empty,Color.Black,Color.Wheat);

//保存到桌面save.jpg
string directory = System.Environment.GetFolderPath(System.Environment.SpecialFolder.DesktopDirectory);
bmp.Save(directory + "\\save.png", ImageFormat.Png);
}

C#實現圖片疊加，圖片上嵌入文字，文字生成圖片的方法