[cscore] Add wpigui-based USB camera viewer

2026-06-24 01:31:46 +00:00 · 2020-08-29 11:30:45 -07:00
parent b83709b269
commit 4cf6947af7
4 changed files with 171 additions and 13 deletions
--- a/cscore/examples/usbviewer/usbviewer.cpp
+++ b/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();
+}