How to convert html5 canvas to image to specific size?

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ASP.NET

MVC

C#5.0

I am using a jQuery cropper to resize the image. The cropper makes a canvas of resized image and I have saved the image using file stream successfully as following.

using (FileStream fs = new FileStream(avatarPath, FileMode.Create))
                {
                    using (BinaryWriter bw = new BinaryWriter(fs))
                    {
                        byte[] data =Convert.FromBase64String(imageCanvas);
                        bw.Write(data);
                        bw.Close();
                    }
                    fs.Close();
                }

But the main issue is that the size of the newly saved image is 3-4 times of the original image.

Any suggestion, thanks in advance.