Get Friend's Avator Picture (Steam) - OpenSteamWorks with C#

GetFriendAvators.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using Steam4NET;

namespace FriendManager
{
    class Program
    {
        // 指定されたIDのフレンドのAvatorのビットマップを取得します
        public static Bitmap getFriendAvatorBitmap(ulong friendId)
        {
            Friend friend = new Friend(friendId);
            int avatorHandle = SteamContext.ClientFriends.GetLargeFriendAvatar(friendId);

            uint width = 0;
            uint height = 0;
            if (SteamContext.SteamUtils.GetImageSize(avatorHandle, ref width, ref height))
            {
                uint size = 4 * width * height; // magic number(4) は、rgbaの4byteの意味
                byte[] buf = new byte[size];

                if (SteamContext.SteamUtils.GetImageRGBA(avatorHandle, buf, (int)size))
                {
                    Bitmap b = new Bitmap((int)width, (int)height);
                    for (uint xx = 0; xx < width; xx++)
                    {
                        for (uint yy = 0; yy < height; yy++)
                        {
                            int index = ((int)yy * (int)width + (int)xx) * 4;
                            int rr = buf[index + 0];
                            int gg = buf[index + 1];
                            int bb = buf[index + 2];
                            int aa = buf[index + 3];

                            Color color = Color.FromArgb(aa, rr, gg, bb);
                            b.SetPixel((int)xx, (int)yy, color);
                        }
                    }
                    return b;
                }
            }
            return null;
        }

        // ファイル名から危険な文字を取り除きます
        public static String trimIllegalCode(String input)
        {
            foreach (char c in System.IO.Path.GetInvalidFileNameChars())
            {
                input = input.Replace(c, '_');
            }
            return input;
        }

        // 指定されたIDのフレンドのAvatorを保存します
        public static void saveFriendAvator(String basePath, ulong friendId)
        {
            Friend friend = new Friend(friendId);
            Bitmap b = getFriendAvatorBitmap(friendId);
            if (b != null)
            {
                String filename = "avator-" + trimIllegalCode(friend.GetName()) + ".png";
                b.Save(basePath + filename);
            }
        }

        // すべてのフレンドのavatorを保存します
        public static int saveAllFriendAvators(String basePath)
        {
            int cnt = 0;
            int friendCount = SteamContext.ClientFriends.GetFriendCount((int)EFriendFlags.k_EFriendFlagImmediate);
            for (int x = 0; x < friendCount; ++x)
            {
                ulong friendId = SteamContext.ClientFriends.GetFriendByIndex(x, (int)EFriendFlags.k_EFriendFlagImmediate);
                saveFriendAvator(basePath, friendId);
                cnt++;
            }
            return cnt;
        }

        public static void Main()
        {            
            try
            {
                SteamContext.Initialize();
                MessageBox.Show(saveAllFriendAvators(@"png\avator-") + "件画像ファイルを保存しました");
            }
            catch ( Exception ex )
            {
                Util.MsgBox( "Unable to initialize Steam Context: " + ex.Message + "\n\n" + ex.ToString() );
                return;
            }
        }
    }
}