【VRCAdvent Calendar】VRChatへ外部から文字列を渡すよ（C# only）

string source = "神城アオイ";
string byteStr = "";

foreach (char c in source)
{
     //上位8bitを変換
    string top = Convert.ToString(c >> 8, 16).PadLeft(2, '0');

     //下位8bitを変換
     string buttom = Convert.ToString(c & 0x00FF, 16).PadLeft(2, '0');

     //結合
    byteStr += byteStr = top + buttom;
}

Color[] colors = Array.Empty<Color>();
foreach (char c in byteStr)
    {
    int i = Convert.ToInt32(c.ToString(), 16);
    int d = i / 4;
    int r = i % 4;

    result = colors.Concat(new Color[] { Color.FromArgb(255, 255 / 3 * r, 255 / 3 * d, 255) }).ToArray();
}

int pixelSize = 8;
int imageSize = 1024;

//描画エリアを用意
using Bitmap bitmap = new Bitmap(imageSize, imageSize);
using Graphics graphics = Graphics.FromImage(bitmap);

//黒で塗りつぶす
using SolidBrush brush = new SolidBrush(Color.Black);
graphics.FillRectangle(brush, new Rectangle(0, 0, imageSize, imageSize)
    
//先ほど変換した色で塗りつぶす
for (int j = 0; j < colors.Length; j++)
{
    brush.Color = colors[j];
    Rectangle rect = new Rectangle(pixelSize * j, pixelSize * i, pixelSize, pixelSize);
    graphics.FillRectangle(brush, rect);
}

string ffmpeg = @"D:\home\ffmpeg.exe";
string tmppng = @"D:\home\tmp.png";
string tmpmp4 = @"D:\home\tmp.mp4";

//画像をファイルに保存
bitmap.Save(tmppng, ImageFormat.Png); 


//ffmpeg に渡す引数を生成
string arguments = $" -loop 1 -i {tmppng} -vcodec libx264 -profile:v baseline -pix_fmt yuv420p -t 1 -r 15 {tmpmp4} -y";

using Process process = Process.Start(new ProcessStartInfo(ffmpeg, arguments)
{
    CreateNoWindow = true,
    UseShellExecute = false,
    WindowStyle = ProcessWindowStyle.Hidden
});
process.WaitForExit();

using UdonSharp;
using UnityEngine;
using VRC.SDKBase;
using VRC.SDK3.Video.Components;

[UdonBehaviourSyncMode(BehaviourSyncMode.NoVariableSync)]
public class VideoLoader : UdonSharpBehaviour
{
    public VRCUnityVideoPlayer videoPlayer;
    public VRCUrl vRCUrl;
    public Camera cam;
    public Texture2D tex;
    private Rect _rect;

    void Start()
    {
        _rect = cam.pixelRect;
        SendCustomEvent(nameof(PlayVideo));
    }

    //動画を再生する
    public void PlayVideo()
    {
        videoPlayer.PlayURL(vRCUrl);
    }

    //動画の再生が終わったら、カメラを一瞬Onにする
    public override void OnVideoEnd()
    {
        SendCustomEvent(nameof(EnableCam));
        SendCustomEventDelayedFrames(nameof(DisableCam), 2);
    }

    //カメラの有効化
    public void EnableCam()
    {
        cam.enabled = true;
    }

    //カメラの無効化
    public void DisableCam()
    {
        cam.enabled = false;
    }

    //カメラが捉えた画像を書き込む
    void OnPostRender()
    {
        tex.ReadPixels(_rect, 0, 0, false);
        tex.Apply(false);
    }
}

public string GetByteStringFromImage()
{
    string result = "";
    int y = tex.height - pixelSize / 2;
    for (int ix = 0; ix * pixelSize + pixelSize / 2 < tex.width; ix++)
    {
        int x = ix * pixelSize + pixelSize / 2;
        Color col = tex.GetPixel(x, y).gamma;

        //bが0の時はデータなしなので、ここでスキップ。圧縮ノイズを考慮して0.5以下にした。
        if (col.b < 0.5f) break;
        int s = Mathf.RoundToInt(col.r * 3) + Mathf.RoundToInt(col.g * 3) * 4;
        result += Convert.ToString(s, 16);
    }
    return result;
}

public string GetStringFromByteString(string byteStr)
{
    //一文字が4byteで構成されているので、一文字づつ
    string[] byteStrArray = new string[byteStr.Length / 4];
    for (int i = 0; i < byteStr.Length; i += 4)
    {
        byteStrArray[i / 4] = byteStr.Substring(i, 4);
    }

    string result = string.Empty;
    for (int i = 0; i < byteStrArray.Length; i++)
    {
        int top = Convert.ToByte(byteStrArray[i].Substring(i, 2), 16) << 8;
        int bottom = Convert.ToByte(byteStrArray[i].Substring(i + 2, 2), 16);
        result += (char)(top + bottom);
    };
    return result;
}