绘制不同颜色的文本图片

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private Bitmap strToImage(string str)

{

    Font f = new Font(new FontFamily("宋体"), 10, FontStyle.Regular);

    float fontSizeWidth = 96 / (72 / f.Size); // 字体实际像素宽度  

    float fontSizeHeight = 96 / (72 / f.Size); // 字体实际像素高度  

    

 

    //创建此大小的图片

    Bitmap bmp = new Bitmap(str.Length * (int)(fontSizeWidth), 22);

    Graphics g = Graphics.FromImage(bmp);

    int fIndex= str.IndexOf(findText);

    string startStr = str.Substring(0, fIndex);

   

    float y= (23- (int)fontSizeHeight) / 2;

    g.DrawString(startStr, f, new SolidBrush(System.Drawing.Color.Black), new PointF(fontSizeWidth / 2,y));

    float startLenth = startStr.Length * (int)(fontSizeWidth );

    g.DrawString(findText, f, new SolidBrush(System.Drawing.Color.Red), new PointF(startLenth, y));//绘制红字

    string enStr = str.Substring(fIndex + findText.Length);

    float findTxLenth = findText.Length * (int)(fontSizeWidth );

    g.DrawString(enStr, f, new SolidBrush(System.Drawing.Color.Black), new PointF(startLenth+findTxLenth , y));

    g.Save();

    g.Dispose();

    return bmp;

}