Resizing image proportionally in ASP.NET C# by specifying either Height or Width

Question

I need a code that will allow me to resize images, but with the following functionality:

1) resize image upon upload

2) Resize image proportionally by specifying

Answer 1

Taken from this Stackoverflow answer, I come up with:

public static Image Resize(this Image image, int maxWidth = 0, int maxHeight = 0)
    {
        if (maxWidth == 0)
            maxWidth = image.Width;
        if (maxHeight == 0)
            maxHeight = image.Height;

        var ratioX = (double)maxWidth / image.Width;
        var ratioY = (double)maxHeight / image.Height;
        var ratio = Math.Min(ratioX, ratioY);

        var newWidth = (int)(image.Width * ratio);
        var newHeight = (int)(image.Height * ratio);

        var newImage = new Bitmap(newWidth, newHeight);
        Graphics.FromImage(newImage).DrawImage(image, 0, 0, newWidth, newHeight);
        return newImage;
    }

To resize Image specifying its maxWidth:

var _image = Image.FromStream(Source);
var _thumbImage = _image.Resize(100);

To resize Image specifying its maxHeight:

var _image = Image.FromStream(Source);
var _thumbImage = _image.Resize(maxHeight: 100);