C#中的图像上的WaterMarking？

Question

我想把水印放在图像的中心，diagonally.My代码做得很好，但是水印并不是出现在每个图像的中心，我认为水印文本的定位有问题，我硬编码values.How，我可以写出水印文本定位的通用公式吗？

    private MemoryStream ApplyWaterMark(MemoryStream stream)
        {

            System.Drawing.Image Im = System.Drawing.Image.FromStream(stream);                // 
            Graphics g = Graphics.FromImage(Im);

            // Create a solid brush to write the watermark text on the image
            Brush myBrush = new SolidBrush(System.Drawing.Color.FromArgb(25,
            System.Drawing.Color.LightSteelBlue));

            var f = new System.Drawing.Font(FontFamily.GenericSerif, 30);
            // Calculate the size of the text
            SizeF sz = g.MeasureString("TEST WATER MARK", f);

            int X, Y;
            X = ((int)(Im.Width - sz.Width) / 2)-1162;
            Y = ((int)(Im.Height + sz.Height) / 2)-127;



            g.RotateTransform(-45f);
            g.DrawString("TEST WATER MARK", f, myBrush,new System.Drawing.Point(X, Y));
            g.RotateTransform(45f);

            Im.Save(OutPutStream, ImageFormat.Png);//save image with dynamic watermark

            return OutPutStream;
        }

Answer 1

您可以通过这种方式对角线设置水印

     Bitmap newBitmap = new Bitmap(bitmap);
     Graphics g = Graphics.FromImage(newBitmap);

     // Trigonometry: Tangent = Opposite / Adjacent
     double tangent = (double)newBitmap.Height / 
                      (double)newBitmap.Width;

     // convert arctangent to degrees
     double angle = Math.Atan(tangent) * (180/Math.PI);

     // a^2 = b^2 + c^2 ; a = sqrt(b^2 + c^2)
     double halfHypotenuse =(Math.Sqrt((newBitmap.Height 
                            * newBitmap.Height) +
                            (newBitmap.Width * 
                            newBitmap.Width))) / 2;

     // Horizontally and vertically aligned the string
     // This makes the placement Point the physical 
     // center of the string instead of top-left.
     StringFormat stringFormat = new StringFormat();
     stringFormat.Alignment = StringAlignment.Center;
     stringFormat.LineAlignment=StringAlignment.Center;

     g.RotateTransform((float)angle);            
     g.DrawString(waterMarkText, font, new SolidBrush(color),
                  new Point((int)halfHypotenuse, 0), 
                  stringFormat);

Answer 2

尝试以这种方式计算图像中心的坐标(X，Y)：

int X, Y;
X = (int)(Im.Width / 2 - sz.Width / 2);
Y = (int)(Im.Height / 2 - sz.Height / 2);

Answer 3

底部有多种颜色的水印

public void AddWatermark(string watermarkText, string image, string TColor) 
{       

    System.Drawing.Image bitmap = (System.Drawing.Image)Bitmap.FromFile(Proot + image);
    Font font = new Font("Arial", 12, FontStyle.Bold, GraphicsUnit.Pixel);

    RectangleF rectf = new RectangleF(70, 90, 90, 50);

    Color color = Color.FromArgb(255, 255, 0, 0);
    try
    {
        if (TColor.ToUpper() == "RED")
        {
            color = Color.FromArgb(255, 255, 0, 0);
        }
        else if (TColor.ToUpper() == "WHITE")
        {
            color = Color.FromArgb(255, 255, 255, 255);
        }
        else if (TColor.ToUpper() == "BLACK")
        {
            color = Color.FromArgb(155, 0, 0, 0);
        }
        else if (TColor.ToUpper() == "GREEN")
        {
            color = Color.FromArgb(255, 0, 255, 0);
        }
    }
    catch { }


    //     WHITE (255, 255, 255, 255)
    //     RED   (255, 255, 000, 000)
    //     GREEN (255, 000, 255, 000)
    //     BLUE  (255, 000, 000, 255) 
    //     BLACK (150, 000, 000, 000)
    //     PURPLE(255, 125, 000, 255)
    //     GREY  (255, 128, 128, 128) 
    //     YELLOW(255, 255, 255, 000) 
    //     ORANGE(255, 255, 125, 000)

 //   Point atpoint = new Point(bitmap.Width / 2, bitmap.Height / 2);
    Point atpoint = new Point(bitmap.Width / 2, bitmap.Height - 10);

    SolidBrush brush = new SolidBrush(color);
    Graphics graphics = Graphics.FromImage(bitmap);

    StringFormat sf = new StringFormat();
    sf.Alignment = StringAlignment.Center;
    sf.LineAlignment = StringAlignment.Center;

    graphics.DrawString(watermarkText, font, brush, atpoint, sf);
    graphics.Dispose();
    MemoryStream m = new MemoryStream();
    bitmap.Save(m, System.Drawing.Imaging.ImageFormat.Jpeg);

 //   Response.WriteFile("images/DefaultLogo.png", true);
    m.WriteTo(Response.OutputStream);

    m.Dispose();
    base.Dispose();
}