Resize the image in C# for the size that you want, in format of PNG

Resize-Image-C#

int newHeight = 110;
int newWidth = 110;

//REDIMENCIONA A IMAGEM PARA 110X110 EM PNG
if (!string.IsNullOrEmpty(avatarIdAntigo)) _fileService.ExcluirPorId(avatarIdAntigo);
Image streamToImage = Image.FromStream(imagem.InputStream);
Bitmap newImageResized = new Bitmap(newWidth, newHeight);
using (Graphics gr = Graphics.FromImage(newImageResized))
{
    gr.SmoothingMode = SmoothingMode.HighQuality;
    gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
    gr.PixelOffsetMode = PixelOffsetMode.HighQuality;
    gr.DrawImage(streamToImage, new Rectangle(0, 0, newWidth, newHeight));
}

var newImageStream = new MemoryStream();
newImageResized.Save(newImageStream, ImageFormat.Png);

_fileService.Adicionar(newImageStream,
    new GridFSImportSettings()
    {
        FileName = filename,
        ContentType = "image/png",
        Id = avatarId
    });