如何实现Windows平台RTMP播放器/RTSP播放器播放窗口添加OSD文字叠加

好多开发者在做Windows平台特别是单屏多画面显示时，希望像监控摄像机一样，可以在播放画面添加OSD台标，以实现字符叠加效果，大多开发者可很轻松的实现以上效果，针对此，本文以大牛直播SDK （Github）的Windows平台demo为例，简单介绍下具体实现：

Windows平台RTMP播放器、RTSP播放器C++ demo

Windows平台C++的demo，以录像过程为例，动态在左上角显示个闪动的图标+当前时间，具体效果如下：

​

核心代码

std::shared_ptr<nt_argb_image_logo> CSmartPlayerDlg::MakeLogo()
{
	std::shared_ptr<nt_argb_image_logo> logo_image;

	if (!is_init_gdi_plus_ok_)
		return logo_image;

	if (!recoder_image_)
	{
		static bool is_load_image_failed = false;

		if (!is_load_image_failed)
		{
			recoder_image_.reset(Gdiplus::Image::FromFile(_T("red_circle.png")));

			if (recoder_image_ && Gdiplus::Ok != recoder_image_->GetLastStatus())
			{
				is_load_image_failed = true;
				recoder_image_.reset();
			}
		}
	}

	is_has_recoder_image_ = !is_has_recoder_image_;

	if (!recoder_image_)
	{
		is_has_recoder_image_ = false;
	}

	if (m_hWnd == nullptr || !::IsWindow(m_hWnd))
		return logo_image;

	if (cur_logo_font_name_.empty())
	{
		cur_logo_font_name_ = FindLogoFontName();
	}

	if (cur_logo_font_name_.empty())
	{
		return logo_image;
	}

	Gdiplus::FontFamily font_family(cur_logo_font_name_.c_str());
	if (!font_family.IsAvailable())
	{
		return logo_image;
	}

	Gdiplus::Font font(&font_family, 10, Gdiplus::FontStyleBold, Gdiplus::Unit::UnitPoint);
	if (!font.IsAvailable())
	{
		return logo_image;
	}

	// 白色
	Gdiplus::SolidBrush solid_brush(Gdiplus::Color(255, 255, 255));
	Gdiplus::Graphics  graphics(m_hWnd);

	if (Gdiplus::Ok != graphics.GetLastStatus())
	{
		return logo_image;
	}

	int recoder_image_w = 18;
	int recoder_image_h = 18;

	if (recoder_image_)
	{
		recoder_image_w = recoder_image_->GetWidth();
		recoder_image_h = recoder_image_->GetHeight();
	}

	auto image_w = recoder_image_w + 2 + 5;
	auto image_h = recoder_image_h + 5 + 5;

	graphics.SetTextRenderingHint(Gdiplus::TextRenderingHint::TextRenderingHintClearTypeGridFit);

	auto cur_time_str = MakeCurTimerStr();

	Gdiplus::RectF bounding_box(0, 0, 0, 0);
	graphics.MeasureString(cur_time_str.c_str(), -1, &font, Gdiplus::PointF(0, 0), &bounding_box);

	Gdiplus::SizeF text_size(0, 0);
	bounding_box.GetSize(&text_size);

	image_w += (int)text_size.Width;
	image_h = image_h > ((int)text_size.Height) ? image_h : ((int)text_size.Height);

	image_w += 2;
	image_h += 2;

	image_w = ByteAlign(image_w, 4);
	image_h = ByteAlign(image_h, 4);

	Gdiplus::Bitmap   bitmap(image_w, image_h, PixelFormat32bppARGB);

	if (Gdiplus::Ok != bitmap.GetLastStatus())
	{
		return logo_image;
	}

	Gdiplus::Graphics g(&bitmap);

	if (Gdiplus::Ok != g.GetLastStatus())
	{
		return logo_image;
	}

	int r_left = 2;
	int r_top = (image_h / 2) - (recoder_image_h / 2);
	r_top -= 1;

	if (is_has_recoder_image_)
	{
		g.DrawImage(recoder_image_.get(), r_left, r_top);
	}

	r_left += recoder_image_w;
	r_left += 5;

	r_top = (image_h / 2) - (text_size.Height / 2);

	g.DrawString(cur_time_str.c_str(), -1, &font, Gdiplus::PointF(r_left, r_top), &solid_brush);

	Gdiplus::BitmapData locked_bitmapData;

	if (Gdiplus::Ok == bitmap.LockBits(nullptr, Gdiplus::ImageLockModeRead, PixelFormat32bppARGB, &locked_bitmapData))
	{
		auto buffer_size = locked_bitmapData.Stride * locked_bitmapData.Height;

		std::unique_ptr<NT_BYTE[]> buffer(new NT_BYTE[buffer_size]);

		if (buffer)
		{
			logo_image = std::make_shared<nt_argb_image_logo>(locked_bitmapData.Width, locked_bitmapData.Height);
			logo_image->stride_ = locked_bitmapData.Stride;

			memcpy(buffer.get(), locked_bitmapData.Scan0, buffer_size);

			logo_image->data_.swap(buffer);
		}

		bitmap.UnlockBits(&locked_bitmapData);
	}

	return logo_image;
}

Windows平台RTMP播放器、RTSP播放器C# demo

Windows平台C#的demo，添加了“设置台标”选择框，在player窗口左上角显示“叠加字符展示”，具体内容、坐标可自定义，具体效果如下：

​

核心代码

        //设置OSD文本
        private void DrawOSD(string draw_text)
        {

            // gdi 绘制的话，文本请自己绘制
            if (is_gdi_render_)
                return;

            if (player_handle_ == IntPtr.Zero)
                return;

            if (draw_text == null || draw_text.Length < 1)
            {
                NTSmartPlayerSDK.NT_SP_SetRenderARGBLogo(player_handle_, IntPtr.Zero, 0, 0, 0, 0, 0, 0, 0);
                return;
            }

            Graphics graphics = this.CreateGraphics();

            SolidBrush solid_brush = new SolidBrush(Color.FromArgb(255, 255, 255));

            graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;

            SizeF text_size = new SizeF();
            text_size = graphics.MeasureString(draw_text, this.Font);

            int image_w = (int)text_size.Width + 4;
            int image_h = (int)text_size.Height + 4;

            image_w = (int)ByteAlign((UInt32)image_w, 4);
            image_h = (int)ByteAlign((UInt32)image_h, 4);

            Bitmap bmp = new Bitmap(image_w, image_h, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

            Graphics g = Graphics.FromImage(bmp);

            g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;

            float left = image_w / 2 - text_size.Width / 2;
            float top = image_h / 2 - text_size.Height / 2;

            g.DrawString(draw_text, this.Font, solid_brush, left, top);

            Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);

            System.Drawing.Imaging.BitmapData bmp_data = bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat);

            IntPtr ptr = bmp_data.Scan0;
            int strdie = Math.Abs(bmp_data.Stride);

            NTSmartPlayerSDK.NT_SP_SetRenderARGBLogo(player_handle_, ptr, strdie, bmp_data.Width,
                bmp_data.Height, 6, 6, bmp_data.Width, bmp_data.Height);

            // Unlock the bits.
            bmp.UnlockBits(bmp_data);
        }
    }

注意，如果GDI模式下，我们数据回调到上层绘制的，这样加起来更简单：

            if (btn_check_add_osd.Checked)
            {
                string draw_text = "叠加字符展示";

                Graphics graphics = this.CreateGraphics();

                SolidBrush solid_brush = new SolidBrush(Color.FromArgb(255, 255, 255));

                graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;

                g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;

                float left = playWnd.Left + 4;
                float top = playWnd.Top + 4;

                g.DrawString(draw_text, this.Font, solid_brush, left, top);
            }

感兴趣的开发者可自行尝试。