Invalid Parameter Used

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Dear All, I have created a function to resize an image and save it to the
server. This is the code:-

try
{
System.Drawing.Image NewImg;

System.Drawing.Image.GetThumbnailImageAbort dummyCallBack =
new System.Drawing.Image.GetThumbnailImageAbort(Thumbn ailCallback);

NewImg = fullSizeImg.GetThumbnailImage(image_width, image_height,
dummyCallBack, IntPtr.Zero);
NewImg.Save(path + image_name);

int x = image_width;
int y = image_height;
string image_path = path + "\\" + image_name;
Image oImg = Image.FromFile(image_path);
Bitmap bmp = new Bitmap(x,y);

System.Drawing.Imaging.Encoder Enc = System.Drawing.Imaging.Encoder.
Transformation;
EncoderParameters EncParms = new EncoderParameters(1);
EncoderParameter EncParm;

Graphics gr = Graphics.FromImage(bmp);
gr.CompositingQuality = CompositingQuality.HighQuality;
gr.SmoothingMode = SmoothingMode.HighQuality;
gr.InterpolationMode = InterpolationMode.HighQualityBicubic;

gr.DrawImage(oImg, 0, 0, x, y);
gr.Save();

EncParms.Param = new EncoderParameter[]
{
new EncoderParameter(Enc,(long)EncoderValue.Compressio nLZW),
new EncoderParameter(System.Drawing.Imaging.Encoder.Qu ality, 100L)
};
ImageCodecInfo ici ;

ici = GetProperEncoder(image_name);

bmp.Save(image_path, ici, EncParms);
oImg.Dispose();
bmp.Dispose();

}
catch (Exception e)
{
Console.WriteLine("Caught: {0}",e.Message);
}

However I am getting an exception on this line :-

bmp.Save(image_path, ici, EncParms);

The exception is

System.Object {System.ArgumentException} "Invalid Parameter Used"

Can anybody help me please? Thanks for your help and time