技术背景
我们在做Windows平台RTMP推送、轻量级RTSP服务的时候，遇到过这样的技术需求，除了常规的png图片水印外，开发者希望能在桌面或摄像头上，叠加上实时时间和位置信息，并保存到图像里。
技术实现
本文以大牛直播SDK的摄像头采集+动态文字水印为例，谈谈如何实现的，简单来说，这块分两步，第一步，如何从文字里面获取到rgb数据，第二步，如何吧rgb数据叠加到摄像头上？
废话不多说，先上图，选中采集摄像头和摄像头添加文字水印，如果需要默认打开动态文字水印，直接打开即可，如需关闭，随时可以关闭或二次打开：
本文以启动个轻量级RTSP服务为例，效果如下，可以清楚的看到右侧播放端，显示实时更新的文字信息（更新间隔，可以自行设置）：
打开摄像头添加文字水印：
ini
private void btn_text_osd_Click(object sender, EventArgs e)
{
if (btn_text_osd.Text.Equals("打开动态文字水印"))
{
if (!timer_clock_.Enabled)
{
timer_clock_.Enabled = true;
}
enable_layer(get_text_layer_index(), true);
btn_text_osd.Text = "关闭动态文字水印";
is_enable_text_watermarker_ = true;
}
else
{
if (!is_enable_publish_random_userdata_)
{
timer_clock_.Enabled = false;
}
enable_layer(get_text_layer_index(), false);
btn_text_osd.Text = "打开动态文字水印";
is_enable_text_watermarker_ = false;
}
}添加文字水印图层：
ini
private async void AddWaterMarkerLayer()
{
Bitmap bitmap = null;
try
{
string format = "yyyy-MM-dd HH:mm:ss.fff";
StringBuilder sb = new StringBuilder();
sb.Append("施工单位：上海视沃信息科技有限公司");
sb.Append("\r\n");
sb.Append("施工时间：");
sb.Append(DateTime.Now.DayOfWeek.ToString());
sb.Append(" ");
sb.Append(DateTime.Now.ToString(format));
sb.Append("\r\n");
sb.Append("当前位置：上海市");
string str = sb.ToString();
bitmap = GenerateBitmap(str);
}
catch (Exception)
{
return;
}
if (null == bitmap)
return;
int x = 0;
int y = 200;
UpdateLayerRegion(get_text_layer_index(), x, y, bitmap);
enable_layer(get_text_layer_index(), true);
await Task.Delay(30);
post_argb8888_layer_image(get_text_layer_index(), bitmap);
}投递图层数据：
ini
/*
* SmartPublisherDemoDlg.cs
* Author: daniusdk.com
*/
public void post_argb8888_layer_image(int index, Bitmap bitmap)
{
if (index < 0 || null == bitmap)
return;
if (!is_running())
return;
Rectangle rect = new Rectangle(0, 0, bitmap.Width, bitmap.Height);
System.Drawing.Imaging.BitmapData bmp_data = bitmap.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadOnly, bitmap.PixelFormat);
IntPtr ptr = bmp_data.Scan0;
int stride = bmp_data.Stride;
if (stride < 0)
stride = -stride;
NT_PB_Image pb_image = new NT_PB_Image();
pb_image.format_ = (int)NT.NTSmartPublisherDefine.NT_PB_E_IMAGE_FORMAT.NT_PB_E_IMAGE_FORMAT_ARGB;
pb_image.width_ = bmp_data.Width;
pb_image.height_ = bmp_data.Height;
pb_image.timestamp_ = 0;
pb_image.cb_size_ = (UInt32)Marshal.SizeOf(pb_image);
pb_image.stride_ = new Int32[NTSmartPublisherDefine.NT_PB_IMAGE_MAX_PLANE_NUM];
pb_image.stride_[0] = stride;
pb_image.plane_size_ = new Int32[NTSmartPublisherDefine.NT_PB_IMAGE_MAX_PLANE_NUM];
pb_image.plane_size_[0] = pb_image.stride_[0] * bmp_data.Height;
pb_image.plane_ = new IntPtr[NTSmartPublisherDefine.NT_PB_IMAGE_MAX_PLANE_NUM];
pb_image.plane_[0] = ptr;
for (int i = 1; i < NTSmartPublisherDefine.NT_PB_IMAGE_MAX_PLANE_NUM; ++i)
{
pb_image.stride_[i] = 0;
pb_image.plane_size_[i] = 0;
pb_image.plane_[i] = IntPtr.Zero;
}
IntPtr image_ptr = Marshal.AllocHGlobal(Marshal.SizeOf(pb_image));
Marshal.StructureToPtr(pb_image, image_ptr, false);
if (is_running())
{
if (shared_lock_.TryEnterReadLock(enter_read_lock_timeout_ms_))
{
try
{
if (is_running())
NTSmartPublisherSDK.NT_PB_PostLayerImage(publisher_handle_, 0, index, image_ptr, 0, IntPtr.Zero);
}
finally
{
shared_lock_.ExitReadLock();
}
}
}
Marshal.FreeHGlobal(image_ptr);
bitmap.UnlockBits(bmp_data);
}再说如何实现两个图层：
ini
if (btn_check_camera_input_.Checked && btn_add_osd_to_camera_.Checked)
{
if (-1 != cur_sel_camera_index_
&& -1 != cur_sel_camera_resolutions_index_
&& -1 != cur_sel_camera_frame_rate_index_)
{
NT_PB_CameraLayerConfigV2 camera_layer_c0 = new NT_PB_CameraLayerConfigV2();
CameraInfo camera = cameras_[cur_sel_camera_index_];
NT_PB_VideoCaptureCapability cap = camera.capabilities_[cur_sel_camera_resolutions_index_];
camera_layer_c0.device_unique_id_utf8_ = camera.id_;
type = (Int32)NTSmartPublisherDefine.NT_PB_E_LAYER_TYPE.NT_PB_E_LAYER_TYPE_CAMERA;
fill_layer_base(camera_layer_c0, out camera_layer_c0.base_, type, index, true, 0, 0, cap.width_, cap.height_);
camera_layer_index_ = camera_layer_c0.base_.index_;
if (btn_check_flip_horizontal_camera_.Checked)
{
camera_layer_c0.is_flip_horizontal_ = 1;
}
else
{
camera_layer_c0.is_flip_horizontal_ = 0;
}
if (btn_check_flip_vertical_camera_.Checked)
{
camera_layer_c0.is_flip_vertical_ = 1;
}
else
{
camera_layer_c0.is_flip_vertical_ = 0;
}
// 这种叠加模式下不要旋转，否则变形厉害, 要么就定好一个角度，调整宽高，但不要动态旋转
camera_layer_c0.rotate_degress_ = 0;
if (add_layer_config(camera_layer_c0, type))
index++;
//第二层：文字水印
//叠加的文本层
NT_PB_ExternalVideoFrameLayerConfig text_layer = new NT_PB_ExternalVideoFrameLayerConfig();
type = (Int32)NTSmartPublisherDefine.NT_PB_E_LAYER_TYPE.NT_PB_E_LAYER_TYPE_EXTERNAL_VIDEO_FRAME;
fill_layer_base(text_layer, out text_layer.base_, type, index, true, 0, 0, 64, 64);
if (add_layer_config(text_layer, type))
text_layer_index_ = index++;
}
NTSmartPublisherSDK.NT_PB_SetFrameRate(publisher_handle_, (uint)(cur_sel_camera_frame_rate_index_ + 1));
}如果需要更新图层位置：
ini
public bool update_layer_region(int index, int x, int y, int w, int h)
{
if (index < 1)
return false;
if (is_empty_handle())
return false;
NT_PB_RectRegion region = new NT_PB_RectRegion();
region.x_ = x;
region.y_ = y;
region.width_ = w;
region.height_ = h;
return NTBaseCodeDefine.NT_ERC_OK == NTSmartPublisherSDK.NT_PB_UpdateLayerRegion(publisher_handle_, 0, index, ref region);
}动态打开关闭图层：
arduino
public bool enable_layer(int index, bool enable)
{
if (index < 1)
return false;
if (is_empty_handle())
return false;
return NTBaseCodeDefine.NT_ERC_OK == NTSmartPublisherSDK.NT_PB_EnableLayer(publisher_handle_, 0, index, enable ? 1 : 0);
}总结
Windows平台添加动态文字水印，首先确保从文字拿到rgb数据，然后，设置两个图层，摄像头或者屏幕数据，作为底层，上层添加文字图层，如果需要实时更新，有个定制器，刷新即可，感兴趣的开发者，可以单独和我交流。