.NET (Core and Framework)

private StringBuilder builder = new StringBuilder();

public string RemoveExtraSpaces(string inputString)
{
    builder.Clear();
    int length = inputString.Length;
    if (length > 0)
    {
        builder.Append(inputString[0]);
        for (int loop1 = 1; loop1 < length; loop1++)
            if (inputString[loop1 - 1] != ' ' || inputString[loop1] != ' ')
                builder.Append(inputString[loop1]);
    }
    return builder.ToString();
}

OutOfMemoryException 	
The file does not have a valid image format.
-or-
GDI+ does not support the pixel format of the file.