Its fine working.Thanks.I have one more doubt regarding watermark text size.I have same size images.In one image,watermark text is large font.In another one image small font size.I want watermark text as standard format,size and also according to image size.
below code for text size.
SizeF textSize = graphic.MeasureString(watermark, myFont);

int x =100;
int y= 100;
PointF pointF = new PointF(x, y);
graphic.DrawString(watermark, myFont, brush, pointF);
x += Convert.ToInt32(textSize.Width);
y += Convert.ToInt32(textSize.Height);

If u want please verify my earlier attachment.