[cscore] Add wpigui-based USB camera viewer

CMakeLists.txt

@@ -120,6 +120,11 @@ endif()
 add_subdirectory(wpiutil)
 add_subdirectory(ntcore)
 
+if (WITH_SIMULATION_MODULES AND NOT USE_EXTERNAL_HAL)
+    add_subdirectory(imgui)
+    add_subdirectory(wpigui)
+endif()
+
 if (NOT WITHOUT_CSCORE)
     set(CSCORE_DEP_REPLACE ${CSCORE_DEP_REPLACE_IMPL})
     set(CAMERASERVER_DEP_REPLACE ${CAMERASERVER_DEP_REPLACE_IMPL})
@@ -137,8 +142,6 @@ if (NOT WITHOUT_CSCORE)
 endif()
 
 if (WITH_SIMULATION_MODULES AND NOT USE_EXTERNAL_HAL)
-    add_subdirectory(imgui)
-    add_subdirectory(wpigui)
     add_subdirectory(simulation)
 endif()
 

cscore/CMakeLists.txt

@@ -52,10 +52,18 @@ install(EXPORT cscore DESTINATION ${cscore_config_dir})
 SUBDIR_LIST(cscore_examples "${CMAKE_CURRENT_SOURCE_DIR}/examples")
 foreach(example ${cscore_examples})
     file(GLOB cscore_example_src examples/${example}/*.cpp)
+    unset(add_libs)
+    if(${example} STREQUAL "usbviewer")
+        if(TARGET wpigui)
+            set(add_libs wpigui)
+        else()
+            unset(cscore_example_src)
+        endif()
+    endif()
     if(cscore_example_src)
         add_executable(cscore_${example} ${cscore_example_src})
         wpilib_target_warnings(cscore_${example})
-        target_link_libraries(cscore_${example} cscore)
+        target_link_libraries(cscore_${example} cscore ${add_libs})
         set_property(TARGET cscore_${example} PROPERTY FOLDER "examples")
     endif()
 endforeach()

cscore/build.gradle

@@ -170,17 +170,50 @@ nativeUtils.exportsConfigs {
 model {
     components {
         examplesMap.each { key, value ->
-            "${key}"(NativeExecutableSpec) {
-                targetBuildTypes 'debug'
-                binaries.all {
-                    lib project: ':wpiutil', library: 'wpiutil', linkage: 'shared'
-                    lib library: 'cscore', linkage: 'shared'
+            if (key == "usbviewer") {
+                if (!project.hasProperty('onlylinuxathena') && !project.hasProperty('onlylinuxraspbian') && !project.hasProperty('onlylinuxaarch64bionic')) {
+                    "${key}"(NativeExecutableSpec) {
+                        targetBuildTypes 'debug'
+                        binaries.all {
+                            lib project: ':wpiutil', library: 'wpiutil', linkage: 'shared'
+                            lib project: ':wpigui', library: 'wpigui', linkage: 'static'
+                            lib library: 'cscore', linkage: 'shared'
+                            nativeUtils.useRequiredLibrary(it, 'imgui_static')
+                            if (it.targetPlatform.name == nativeUtils.wpi.platforms.roborio || it.targetPlatform.name == nativeUtils.wpi.platforms.raspbian || it.targetPlatform.name == nativeUtils.wpi.platforms.aarch64bionic) {
+                                it.buildable = false
+                                return
+                            }
+                            if (it.targetPlatform.operatingSystem.isWindows()) {
+                                it.linker.args << 'Gdi32.lib' << 'Shell32.lib' << 'd3d11.lib' << 'd3dcompiler.lib'
+                            } else if (it.targetPlatform.operatingSystem.isMacOsX()) {
+                                it.linker.args << '-framework' << 'Metal' << '-framework' << 'MetalKit' << '-framework' << 'Cocoa' << '-framework' << 'IOKit' << '-framework' << 'CoreFoundation' << '-framework' << 'CoreVideo' << '-framework' << 'QuartzCore'
+                            } else {
+                                it.linker.args << '-lX11'
+                            }
+                        }
+                        sources {
+                            cpp {
+                                source {
+                                    srcDirs 'examples/' + "${key}"
+                                    include '**/*.cpp'
+                                }
+                            }
+                        }
+                    }
                 }
-                sources {
-                    cpp {
-                        source {
-                            srcDirs 'examples/' + "${key}"
-                            include '**/*.cpp'
+            } else {
+                "${key}"(NativeExecutableSpec) {
+                    targetBuildTypes 'debug'
+                    binaries.all {
+                        lib project: ':wpiutil', library: 'wpiutil', linkage: 'shared'
+                        lib library: 'cscore', linkage: 'shared'
+                    }
+                    sources {
+                        cpp {
+                            source {
+                                srcDirs 'examples/' + "${key}"
+                                include '**/*.cpp'
+                            }
                         }
                     }
                 }

cscore/examples/usbviewer/usbviewer.cpp

@@ -0,0 +1,114 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2020 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include <atomic>
+#include <thread>
+#include <vector>
+
+#define IMGUI_DEFINE_MATH_OPERATORS
+#include <imgui.h>
+#include <imgui_internal.h>
+#include <opencv2/core/core.hpp>
+#include <opencv2/imgproc.hpp>
+#include <wpi/raw_ostream.h>
+#include <wpi/spinlock.h>
+#include <wpigui.h>
+
+#include "cscore.h"
+#include "cscore_cv.h"
+
+namespace gui = wpi::gui;
+
+int main() {
+  std::atomic<cv::Mat*> latestFrame;
+  std::vector<cv::Mat*> sharedFreeList;
+  wpi::spinlock sharedFreeListMutex;
+  std::vector<cv::Mat*> sourceFreeList;
+  std::atomic<bool> stopCamera{false};
+
+  cs::UsbCamera camera{"usbcam", 0};
+  camera.SetVideoMode(cs::VideoMode::kMJPEG, 640, 480, 30);
+  cs::CvSink cvsink{"cvsink"};
+  cvsink.SetSource(camera);
+
+  std::thread thr([&] {
+    cv::Mat frame;
+    while (!stopCamera) {
+      // get frame from camera
+      uint64_t time = cvsink.GrabFrame(frame);
+      if (time == 0) {
+        wpi::outs() << "error: " << cvsink.GetError() << '\n';
+        continue;
+      }
+
+      // get or create a mat, prefer sourceFreeList over sharedFreeList
+      cv::Mat* out;
+      if (!sourceFreeList.empty()) {
+        out = sourceFreeList.back();
+        sourceFreeList.pop_back();
+      } else {
+        {
+          std::scoped_lock lock(sharedFreeListMutex);
+          for (auto mat : sharedFreeList) sourceFreeList.emplace_back(mat);
+          sharedFreeList.clear();
+        }
+        if (!sourceFreeList.empty()) {
+          out = sourceFreeList.back();
+          sourceFreeList.pop_back();
+        } else {
+          out = new cv::Mat;
+        }
+      }
+
+      // convert to RGBA
+      cv::cvtColor(frame, *out, cv::COLOR_BGR2RGBA);
+
+      // make available
+      auto prev = latestFrame.exchange(out);
+
+      // put prev on free list
+      if (prev) sourceFreeList.emplace_back(prev);
+    }
+  });
+
+  gui::CreateContext();
+  gui::Initialize("Hello World", 1024, 768);
+  gui::Texture tex;
+  gui::AddEarlyExecute([&] {
+    auto frame = latestFrame.exchange(nullptr);
+    if (frame) {
+      // create or update texture
+      if (!tex || frame->cols != tex.GetWidth() ||
+          frame->rows != tex.GetHeight()) {
+        tex = gui::Texture(gui::kPixelRGBA, frame->cols, frame->rows,
+                           frame->data);
+      } else {
+        tex.Update(frame->data);
+      }
+      // put back on shared freelist
+      std::scoped_lock lock(sharedFreeListMutex);
+      sharedFreeList.emplace_back(frame);
+    }
+
+    ImGui::SetNextWindowSize(ImVec2(640, 480), ImGuiCond_FirstUseEver);
+    if (ImGui::Begin("Video")) {
+      // render to window (best fit)
+      if (tex && tex.GetWidth() != 0 && tex.GetHeight() != 0) {
+        auto drawList = ImGui::GetWindowDrawList();
+        ImVec2 windowPos = ImGui::GetWindowPos();
+        ImVec2 imageMin = ImGui::GetWindowContentRegionMin();
+        ImVec2 imageMax = ImGui::GetWindowContentRegionMax();
+        gui::MaxFit(&imageMin, &imageMax, tex.GetWidth(), tex.GetHeight());
+        drawList->AddImage(tex, windowPos + imageMin, windowPos + imageMax);
+      }
+    }
+    ImGui::End();
+  });
+  gui::Main();
+  stopCamera = true;
+  thr.join();
+}