http jpg streaming (#161)

Author: nihui

README.md

@@ -28,6 +28,8 @@
 
 :heavy_check_mark: ***NEW FEATURE*** [`cv::imshow` supports Linux framebuffer and Windows](#cvimshow-supports-linux-framebuffer-and-windows)
 
+:heavy_check_mark: ***NEW FEATURE*** [`cv::VideoWriter` supports jpg streaming over http](#cvvideowriter-supports-jpg-streaming-over-http)
+
 |opencv 4.10.0 package size|The official opencv|opencv-mobile|
 |:-:|:-:|:-:|
 |source zip|95.2 MB|8.25 MB|
@@ -610,6 +612,35 @@ int main()
 </td></tr>
 </table>
 
+## `cv::VideoWriter` supports jpg streaming over http
+
+In Linux, `cv::VideoWriter` could be used for streaming images as jpg over http, while it is noop on other platforms. Initialize a `cv::VideoWriter` instance, `open` the writer with name `httpjpg` and a port number, then it will setup a simple http server. You can open the streaming url with a web browser, and image will be shown in the browser as soon as it is sent to the writer. The image size and content can be dynamic, which is useful for streaming frames from a live camera.
+
+```cpp
+#include <opencv2/core/core.hpp>
+#include <opencv2/highgui/highgui.hpp>
+
+int main()
+{
+    cv::VideoCapture cap;
+    cap.open(0);
+
+    cv::VideoWriter http;
+    http.open("httpjpg", 7766);
+
+    // open streaming url http://<server ip>:7766 in web browser
+
+    cv::Mat bgr;
+    while (1)
+    {
+        cap >> bgr;
+        http << bgr;
+    }
+
+    return 0;
+}
+```
+
 # opencv modules included
 
 |module|comment|

highgui/CMakeLists.txt

@@ -10,6 +10,7 @@ set(highgui_srcs
     ${CMAKE_CURRENT_LIST_DIR}/src/highgui.cpp
     ${CMAKE_CURRENT_LIST_DIR}/src/kanna_rotate.cpp
     ${CMAKE_CURRENT_LIST_DIR}/src/videocapture.cpp
+    ${CMAKE_CURRENT_LIST_DIR}/src/videowriter.cpp
 
     # dnn
     ${CMAKE_CURRENT_LIST_DIR}/src/nms.cpp
@@ -18,7 +19,8 @@ set(highgui_srcs
 if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
   list(APPEND highgui_srcs
     ${CMAKE_CURRENT_LIST_DIR}/src/capture_v4l2.cpp
-    ${CMAKE_CURRENT_LIST_DIR}/src/display_fb.cpp)
+    ${CMAKE_CURRENT_LIST_DIR}/src/display_fb.cpp
+    ${CMAKE_CURRENT_LIST_DIR}/src/writer_http.cpp)
 endif()
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Windows")

highgui/include/opencv2/highgui/highgui.hpp

@@ -95,6 +95,28 @@ class CV_EXPORTS_W VideoCapture
     VideoCaptureImpl* const d;
 };
 
+class VideoWriterImpl;
+class CV_EXPORTS_W VideoWriter
+{
+public:
+    VideoWriter();
+
+    ~VideoWriter();
+
+    bool open(const String& name, int port);
+
+    bool isOpened() const;
+
+    void release();
+
+    VideoWriter& operator<<(const Mat& bgr_image);
+
+    void write(const Mat& image);
+
+protected:
+    VideoWriterImpl* const d;
+};
+
 } // namespace cv
 
 #endif // OPENCV_HIGHGUI_HPP

highgui/src/highgui.cpp

@@ -51,7 +51,7 @@
 #if CV_WITH_RK
 #include "jpeg_encoder_rk_mpp.h"
 #endif
-#if defined __linux__
+#if defined __linux__ && !__ANDROID__
 #include "display_fb.h"
 #endif
 

highgui/src/videowriter.cpp

@@ -0,0 +1,144 @@
+//
+// Copyright (C) 2024 nihui
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//         http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include <opencv2/core.hpp>
+#include <opencv2/highgui.hpp>
+
+#include <stdio.h>
+#include <string.h>
+
+#if defined __linux__ && !__ANDROID__
+#include "writer_http.h"
+#endif
+
+namespace cv {
+
+class VideoWriterImpl
+{
+public:
+    VideoWriterImpl();
+
+public:
+    bool is_opened;
+    int width;
+    int height;
+    float fps;
+
+#if defined __linux__ && !__ANDROID__
+    writer_http wt_http;
+#endif
+};
+
+VideoWriterImpl::VideoWriterImpl()
+{
+    is_opened = false;
+    width = 0;
+    height = 0;
+    fps = 0;
+}
+
+VideoWriter::VideoWriter() : d(new VideoWriterImpl)
+{
+}
+
+VideoWriter::~VideoWriter()
+{
+    release();
+
+    delete d;
+}
+
+bool VideoWriter::open(const String& name, int port)
+{
+    if (d->is_opened)
+    {
+        release();
+    }
+
+    if (name == "httpjpg")
+    {
+#if defined __linux__ && !__ANDROID__
+        if (writer_http::supported())
+        {
+            int ret = d->wt_http.open(port);
+            if (ret == 0)
+            {
+                d->is_opened = true;
+            }
+        }
+        else
+#endif
+        {
+        }
+    }
+
+    return d->is_opened;
+}
+
+bool VideoWriter::isOpened() const
+{
+    return d->is_opened;
+}
+
+void VideoWriter::release()
+{
+    if (!d->is_opened)
+        return;
+
+#if defined __linux__ && !__ANDROID__
+    if (writer_http::supported())
+    {
+        d->wt_http.close();
+    }
+    else
+#endif
+    {
+    }
+
+    d->is_opened = false;
+    d->width = 0;
+    d->height = 0;
+    d->fps = 0;
+}
+
+VideoWriter& VideoWriter::operator<<(const Mat& image)
+{
+    write(image);
+
+    return *this;
+}
+
+void VideoWriter::write(const Mat& image)
+{
+    if (!d->is_opened)
+        return;
+
+#if defined __linux__ && !__ANDROID__
+    if (writer_http::supported())
+    {
+        // encode jpg
+        std::vector<uchar> buf;
+        cv::imencode(".JPG", image, buf);
+
+        d->wt_http.write_jpgbuf((const unsigned char*)buf.data(), buf.size());
+    }
+    else
+#endif
+    {
+    }
+}
+
+} // namespace cv