renderer: screenshot by saving render texture to file

.gitignore

@@ -9,3 +9,4 @@ gmon.out*
 cscope*
 test.cpp
 a.out
+*screenshot*

include/renderer.hpp

@@ -17,6 +17,8 @@ namespace renderer{
     void framebuffer_size_callback(GLFWwindow *window, int width, int height);
     void destroy();
 
+    void saveScreenshot(bool forceFullHD=false);
+
     Shader* getRenderShader();
     RenderSet& getChunksToRender();
     oneapi::tbb::concurrent_queue<chunkmesher::MeshData*>& getMeshDataQueue();

src/main.cpp

@@ -155,4 +155,7 @@ void processInput(GLFWwindow *window)
     // Reset blockpicking if enough time has passed
     if(glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_1) == GLFW_RELEASE && glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_2) == GLFW_RELEASE) blockpick = false;
 
+    if(glfwGetKey(window, GLFW_KEY_F2) == GLFW_PRESS) renderer::saveScreenshot();
+    if(glfwGetKey(window, GLFW_KEY_F3) == GLFW_PRESS) renderer::saveScreenshot(true);
+
 }

src/renderer.cpp

@@ -7,6 +7,8 @@
 #include "chunkmesher.hpp"
 #include "globals.hpp"
 #include "stb_image.h"
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+#include "stb_image_write.h"
 
 namespace renderer{
     RenderSet chunks_torender;
@@ -240,6 +242,30 @@ namespace renderer{
 		renderTexDepthBuffer);
     }
 
+    void saveScreenshot(bool forceFullHD){
+	int old_screenWidth = screenWidth;
+	int old_screenHeight = screenHeight;
+
+	if(forceFullHD){
+	    resize_framebuffer(1920, 1080);
+	    // Do a render pass
+	    render();
+	}
+
+	// Bind the render frame buffer
+	glBindFramebuffer(GL_FRAMEBUFFER, renderTexFrameBuffer);
+	glPixelStorei(GL_PACK_ALIGNMENT, 1);
+	// Save the framebuffer in a byte array
+	GLubyte data[screenWidth*screenHeight*3];
+	glReadPixels(0, 0, screenWidth, screenHeight, GL_RGB, GL_UNSIGNED_BYTE, data);
+	// Save the byte array onto a texture
+	stbi_flip_vertically_on_write(1);
+	stbi_write_png(forceFullHD ? "screenshot_fullhd.png" : "screenshot.png", screenWidth,
+		screenHeight, 3, data, screenWidth*3);
+
+	if(forceFullHD) resize_framebuffer(old_screenWidth, old_screenHeight);
+    }
+
     void destroy(){
 	delete theShader;
     }