Unity读取本地JPG图片另存为png图片，png图片要很小作为icon使用，如何实现？

我想用Unity读取本地JPG图片然后另存为很小png图片作为icon图标使用，但是IO读取byte[]保存和原来大小一样，读取为Texture后保存比原来还大一倍。怎么才能保存为很小图片？

之前做过类似的功能，可以参考一下

    #region 压缩得到用户相册图片-- 上传头像使用

    private string CompressTexture(string imagePath)
    {
        if (string.IsNullOrEmpty(imagePath)) return "";
  
        byte[] fileData = File.ReadAllBytes(imagePath);

        Texture2D tex = new Texture2D((int) (Screen.width), (int) (Screen.height), TextureFormat.RGB24, true);
        tex.LoadImage(fileData);

        float miniSize = Mathf.Max(tex.width, tex.height);

        float scale = 1200.0f / miniSize;
        if (scale > 1.0f)
        {
            scale = 1.0f;
        }

        Texture2D temp = ScaleTexture(tex, (int) (tex.width * scale), (int) (tex.height * scale));
        byte[] pngData = temp.EncodeToJPG();
        string miniImagePath = imagePath.Replace(".png", "_min.jpg");
        File.WriteAllBytes(miniImagePath, pngData);
        Destroy(tex);
        Destroy(temp);
        return miniImagePath;
    }

    private Texture2D ScaleTexture(Texture2D source, int targetWidth, int targetHeight)
    {
        Texture2D result = new Texture2D(targetWidth, targetHeight, source.format, true);
        Color[] rpixels = result.GetPixels(0);
        float incX = ((float) 1 / source.width) * ((float) source.width / targetWidth);
        float incY = ((float) 1 / source.height) * ((float) source.height / targetHeight);
        for (int px = 0; px < rpixels.Length; px++)
        {
            rpixels[px] = source.GetPixelBilinear(incX * ((float) px % targetWidth),
                incY * ((float) Mathf.Floor(px / targetWidth)));
        }

        result.SetPixels(rpixels, 0);
        result.Apply();
        return result;
    }

    #endregion

读取本地jpg之后在界面上显示出来吗？