Specifically it's Font.CreateDynamicFontFromOSFont(), use this script attached to an empty GameObject in the scene.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class TestFontTexture : MonoBehaviour {

    void Start () 
    {
        var font = Font.CreateDynamicFontFromOSFont("Consolas", 12);        
        font.RequestCharactersInTexture("HelloWorld", 20);
        SaveTexture2PNG("./fontTexture.png", (Texture2D)font.material.mainTexture);
    }
    
    void Update () 
    {
        
    }

    void SaveTexture2PNG(string path, Texture2D tex)
    {
        byte[] bytes = tex.EncodeToPNG();
        System.IO.File.WriteAllBytes(path, bytes);
    }
}

After click play it should create a fontTexture.png file containing character glyphs in the Assets folder, only in editor though. In a built game, it just created a completely black image.

since it's OS concerned, I'm using Windows 7 with font Consolas installed and Unity 5.6.5f.

How to make it work in a built game?

Specifically it's Font.CreateDynamicFontFromOSFont(), use this script attached to an empty GameObject in the scene.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class TestFontTexture : MonoBehaviour {

    void Start () 
    {
        var font = Font.CreateDynamicFontFromOSFont("Consolas", 12);        
        font.RequestCharactersInTexture("HelloWorld", 20);
        SaveTexture2PNG("./fontTexture.png", (Texture2D)font.material.mainTexture);
    }
    
    void Update () 
    {
        
    }

    void SaveTexture2PNG(string path, Texture2D tex)
    {
        byte[] bytes = tex.EncodeToPNG();
        System.IO.File.WriteAllBytes(path, bytes);
    }
}

After click play it should create a fontTexture.png file containing character glyphs in the Assets folder, but only in editor though. In the built game it just created a completely black image.

Since it's OS concerned, I'm using Windows 7 with font Consolas installed and Unity 5.6.5f.

How to make it work in a built game?