resize image and add watermark c#
void waterMarkOnBottomRight(Image img, Image watermarkImage, string saveFileName)
{
double imageHeightBrand = Convert.ToDouble(watermarkImage.Height);
double imageWidthBrand = Convert.ToDouble(watermarkImage.Width);
double ratioBrand = imageWidthBrand / imageHeightBrand;
double imageHeightBild = Convert.ToDouble(img.Height); //height of the image to watermark
double imageWidthBild = Convert.ToDouble(img.Width);
var imageWidthTmpBranding = imageWidthBild * 0.2; //the watermark width, but only 20% size of the image to watermark
var imageHeightTmpBranding = imageWidthTmpBranding / ratioBrand; //height of watermark, preserve aspect ratio
int imageWidthBranding = Convert.ToInt32(imageWidthTmpBranding); //convert in into int32 (see method below)
int imageHeightBranding = Convert.ToInt32(imageHeightTmpBranding);
int watermarkX = (int)(imageWidthBild - imageWidthBranding); // Bottom Right
int watermarkY = (int)(imageHeightBild - imageHeightBranding);
using (Graphics g = Graphics.FromImage(img))
g.DrawImage(watermarkImage,
new Rectangle(watermarkX, watermarkY, imageWidthBranding, imageHeightBranding),
new Rectangle(0, 0, (int)imageWidthBrand, (int)imageHeightBrand),
GraphicsUnit.Pixel);
img.Save(saveFileName);
}