Misc (#19)

* get image returns optional<Mat> instead of unique_ptr<Mat>

* introduce complexity

* rename image load function

* add example for a basic reader for binary image files

* fix windows build?

* add a status bar underneath the menu bar

* use status bar in custom_0 example app

* clang formats

* packing w/ pragma push

* add "Save As" functions to image views

* resize over reserve

* rm local override uri

* add simple thread pool

* rename to simple_thread_pool

* get rid of useless renderlib

* document version inc

* extract hardcoded values to in-header

* clang format patch

* clone registered image in custom_0

* document binary-file header

* minor fixes

* clang format

* rm unused render cmake

lib/app/rendering/CvMatRender.hpp

@@ -0,0 +1,52 @@
+#pragma once
+// windows.h must come before GL/GL.h here.
+// clang format would change this, effectively rendering the build broken.
+// clang-format off
+#ifdef _WIN32
+#include <windows.h>
+#include <GL/GL.h>
+#else
+#define GL_SILENCE_DEPRECATION
+#if defined(IMGUI_IMPL_OPENGL_ES2)
+#include <GLES2/gl2.h>
+#endif
+#include <GLFW/glfw3.h>  // Will drag system OpenGL headers
+#endif
+#include <opencv2/core/mat.hpp>
+// clang-format on
+
+namespace pixelarium::application
+{
+/// @brief Renders cv::Mat bitmaps as OpenGL textures.
+class CvMatRender
+{
+   public:
+    // we want the default constructor for the time being
+    // (although it does not make much sense and should
+    // get removed in the future)
+    // as the using AppGLFW constructs it empty as a member
+    // when coming to life.
+    // CvMatRender() = default;
+    CvMatRender(CvMatRender&) = delete;
+    CvMatRender(const CvMatRender&) = delete;
+    CvMatRender(CvMatRender&&) = delete;
+    CvMatRender& operator=(CvMatRender&) = delete;
+    CvMatRender& operator=(CvMatRender&& other) = delete;
+    ~CvMatRender();
+    explicit CvMatRender(const cv::Mat& img);
+
+   public:
+    GLuint Render();
+    GLuint Render(float factor);
+    GLuint Render(size_t width, size_t height);
+    void ResetRenderImage();
+
+   private:
+    cv::Mat img_;
+    const cv::Mat& base_;
+    GLuint texture_;
+
+    GLuint uploadTexture();
+};
+
+}  // namespace pixelarium::application