なつねこメモ

// List<Texture2D> textures;

private void CreateTexture2DArray()
{
    var path = EditorUtility.SaveFilePanel("保存", "Assets", "tex2darray", "asset");
    if (string.IsNullOrWhiteSpace(path))
        return;

    var tex2dArray = new Texture2DArray(textures[0].width, textures[1].height, textures.Count, TextureFormat.ARGB32, true)
    {
        filterMode = FilterMode.Bilinear,
        wrapMode = TextureWrapMode.Clamp,
    };

    for (var i = 0; i < textures.Count; i++)
    {
        var texture = CreateReadableTexture2D(textures[i]);
        tex2dArray.SetPixels(texture.GetPixels(0), i, 0);
        DestroyImmediate(texture);
    }

    tex2dArray.Apply();

    AssetDatabase.CreateAsset(tex2dArray, Path.Combine("Assets", path.Substring(Application.dataPath.Length + 1)));
}

private static Texture2D CreateReadableTexture2D(Texture2D texture)
{
    var renderTexture = RenderTexture.GetTemporary(texture.width, texture.height, 0, RenderTextureFormat.Default, RenderTextureReadWrite.Linear);
    Graphics.Blit(texture, renderTexture);

    var previousTexture = RenderTexture.active;
    RenderTexture.active = renderTexture;

    var readableTexture = new Texture2D(texture.width, texture.height);
    readableTexture.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
    readableTexture.Apply();

    RenderTexture.active = previousTexture;
    RenderTexture.ReleaseTemporary(renderTexture);

    return readableTexture;
}