How render per pixels

OpenGL OpenGL: Basic Coding
1

Hello!
I have a project and I need to render per pixels.
Specifically I want take in a buffer (or array or something) all the pixels by color, then apply some manipulations, then render on screen.
For example I have this code (a green cube in the scene)


// Include standard headers
#include <stdio.h>
#include <stdlib.h>

// Include GLEW
#include <glew.h>

// Include GLFW
#include <glfw3.h>
GLFWwindow* window;

// Include GLM
#include <glm.hpp>
#include <gtc/matrix_transform.hpp>
using namespace glm;

#include "shader.hpp"

int main( void )
{
	// Initialise GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW
" );
		return -1;
	}

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Cube", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.
" );
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	// Initialize GLEW
	glewExperimental = true; // Needed for core profile
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW
");
		return -1;
	}

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

	// Enable depth test
	glEnable(GL_DEPTH_TEST);
	// Accept fragment if it closer to the camera than the former one
	glDepthFunc(GL_LESS); 

	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);

	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "TransformVertexShader.vertexshader", "ColorFragmentShader.fragmentshader" );

	// Get a handle for our "MVP" uniform
	GLuint MatrixID = glGetUniformLocation(programID, "MVP");

	// Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
	glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
	// Camera matrix
	glm::mat4 View       = glm::lookAt(
								glm::vec3(4,3,-3), // Camera is at (4,3,-3), in World Space
								glm::vec3(0,0,0), // and looks at the origin
								glm::vec3(0,1,0)  // Head is up (set to 0,-1,0 to look upside-down)
						   );
	// Model matrix : an identity matrix (model will be at the origin)
	glm::mat4 Model      = glm::mat4(1.0f);
	// Our ModelViewProjection : multiplication of our 3 matrices
	glm::mat4 MVP        = Projection * View * Model; // Remember, matrix multiplication is the other way around

	// Our vertices. Tree consecutive floats give a 3D vertex; Three consecutive vertices give a triangle.
	// A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices
	static const GLfloat g_vertex_buffer_data[] = { 
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f
	};

	// One color for each vertex. They were generated randomly.
	static const GLfloat g_color_buffer_data[] = { 
		0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f
	};

	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

	GLuint colorbuffer;
	glGenBuffers(1, &colorbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);

	do{

		// Clear the screen
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(programID);

		// Send our transformation to the currently bound shader, 
		// in the "MVP" uniform
		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		// 2nd attribute buffer : colors
		glEnableVertexAttribArray(1);
		glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
		glVertexAttribPointer(
			1,                                // attribute. No particular reason for 1, but must match the layout in the shader.
			3,                                // size
			GL_FLOAT,                         // type
			GL_FALSE,                         // normalized?
			0,                                // stride
			(void*)0                          // array buffer offset
		);

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 12*3); // 12*3 indices starting at 0 -> 12 triangles

		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);

		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0 );

	// Cleanup VBO and shader
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteBuffers(1, &colorbuffer);
	glDeleteProgram(programID);
	glDeleteVertexArrays(1, &VertexArrayID);

	// Close OpenGL window and terminate GLFW
	glfwTerminate();

	return 0;
}

How Can I modify my above code, for meet my purpose?
For instance:

  1. collect all the pixel’s colors in a buff
  2. manipulate the color of some pixels
  3. render the buff.

How can I do that?

Thanks

2

You should just upload the pixels to a texture and then render the texture.
Rendering pixel by pixel would possible I think but not very good in terms of performance.

3

[QUOTE=Cornix;1260082]You should just upload the pixels to a texture and then render the texture.
[/QUOTE]
Hello, thanks for reply!
Can you specify, how I can do that?

Thanks a lot!

4

Hello I found a tutorial on how to render on a texture, so the above code become:


// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <iostream>

#include <windows.h>
// Include GLEW
#include <glew.h>

// Include GLFW
#include <glfw3.h>
GLFWwindow* window;

// Include GLM
#include <glm.hpp>
#include <gtc/matrix_transform.hpp>
using namespace glm;

#include "shader.hpp"

int main( void )
{
	// Initialise GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW
" );
		return -1;
	}

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Cube", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.
" );
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	// Initialize GLEW
	glewExperimental = true; // Needed for core profile
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW
");
		return -1;
	}

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

	// Enable depth test
	glEnable(GL_DEPTH_TEST);
	// Accept fragment if it closer to the camera than the former one
	//glDepthFunc(GL_LESS); 

	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);

	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "TransformVertexShader.vertexshader", "ColorFragmentShader.fragmentshader" );

	// Get a handle for our "MVP" uniform
	GLuint MatrixID = glGetUniformLocation(programID, "MVP");

	// Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
	glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
	// Camera matrix
	glm::mat4 View       = glm::lookAt(
								glm::vec3(4,3,-3), // Camera is at (4,3,-3), in World Space
								glm::vec3(0,0,0), // and looks at the origin
								glm::vec3(0,1,0)  // Head is up (set to 0,-1,0 to look upside-down)
						   );
	// Model matrix : an identity matrix (model will be at the origin)
	glm::mat4 Model      = glm::mat4(1.0f);
	// Our ModelViewProjection : multiplication of our 3 matrices
	glm::mat4 MVP        = Projection * View * Model; // Remember, matrix multiplication is the other way around

	// Our vertices. Tree consecutive floats give a 3D vertex; Three consecutive vertices give a triangle.
	// A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices
	static const GLfloat g_vertex_buffer_data[] = { 
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f
	};

	// One color for each vertex. They were generated randomly.
	static const GLfloat g_color_buffer_data[] = { 
		0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f
	};

	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

	GLuint colorbuffer;
	glGenBuffers(1, &colorbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);

	glUseProgram(programID);


		// ---------------------------------------------
	// Render to Texture - specific code begins here
	// ---------------------------------------------

	// The framebuffer, which regroups 0, 1, or more textures, and 0 or 1 depth buffer.
	GLuint FramebufferName = 0;
	glGenFramebuffers(1, &FramebufferName);
	glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);

	// The texture we're going to render to
	GLuint renderedTexture;
	glGenTextures(1, &renderedTexture);
	
	// "Bind" the newly created texture : all future texture functions will modify this texture
	glBindTexture(GL_TEXTURE_2D, renderedTexture);

	// Give an empty image to OpenGL ( the last "0" means "empty" )
	glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, 1024, 768, 0,GL_RGBA, GL_UNSIGNED_BYTE, 0);

	// Poor filtering
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

	// The depth buffer
	GLuint depthrenderbuffer;
	glGenRenderbuffers(1, &depthrenderbuffer);
	glBindRenderbuffer(GL_RENDERBUFFER, depthrenderbuffer);
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, 1024, 768);
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthrenderbuffer);

	//----------------------------

	// Set "renderedTexture" as our colour attachement #0
	glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTexture, 0);

	// Set the list of draw buffers.
	GLenum DrawBuffers[1] = {GL_COLOR_ATTACHMENT0};
	glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers

	// Always check that our framebuffer is ok
	if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
	{
		printf("
FrameBuffer Error
");
		return false;
	}

	
	// The fullscreen quad's FBO
	static const GLfloat g_quad_vertex_buffer_data[] = { 
		-1.0f, -1.0f, 0.0f,
		 1.0f, -1.0f, 0.0f,
		-1.0f,  1.0f, 0.0f,
		-1.0f,  1.0f, 0.0f,
		 1.0f, -1.0f, 0.0f,
		 1.0f,  1.0f, 0.0f,
	};

	GLuint quad_vertexbuffer;
	glGenBuffers(1, &quad_vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, quad_vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_quad_vertex_buffer_data), g_quad_vertex_buffer_data, GL_STATIC_DRAW);

	// Create and compile our GLSL program from the shaders
	GLuint quad_programID = LoadShaders( "Passthrough.vertexshader", "WobblyTexture.fragmentshader" );
	GLuint texID = glGetUniformLocation(quad_programID, "renderedTexture");
	GLuint timeID = glGetUniformLocation(quad_programID, "time");

	do{
		// Render to our framebuffer
		glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);
		glViewport(0,0,1024,768); // Render on the whole framebuffer, complete from the lower left corner to the upper right

		// Clear the screen
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(programID);

		// Send our transformation to the currently bound shader, 
		// in the "MVP" uniform
		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		// 2nd attribute buffer : colors
		glEnableVertexAttribArray(1);
		glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
		glVertexAttribPointer(
			1,                                // attribute. No particular reason for 1, but must match the layout in the shader.
			3,                                // size
			GL_FLOAT,                         // type
			GL_FALSE,                         // normalized?
			0,                                // stride
			(void*)0                          // array buffer offset
		);

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 12*3); // 12*3 indices starting at 0 -> 12 triangles
		
		
		// Render to the screen
		glBindFramebuffer(GL_FRAMEBUFFER, 0);
		glViewport(0,0,1024,768); // Render on the whole framebuffer, complete from the lower left corner to the upper right

		// Clear the screen
		glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(quad_programID);

		
		// Bind our texture in Texture Unit 0
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, renderedTexture);
		// Set our "renderedTexture" sampler to user Texture Unit 0
		glUniform1i(texID, 0);

		glUniform1f(timeID, (float)(glfwGetTime()*10.0f) );

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, quad_vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		// Draw the triangles !
		glDrawArrays(GL_TRIANGLES, 0, 6); // 2*3 indices starting at 0 -> 2 triangles

		glDisableVertexAttribArray(0);



		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);

		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0 );

		// Cleanup VBO and shader
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteBuffers(1, &colorbuffer);
	glDeleteProgram(programID);


	glDeleteFramebuffers(1, &FramebufferName);
	glDeleteTextures(1, &renderedTexture);
	glDeleteRenderbuffers(1, &depthrenderbuffer);
	glDeleteBuffers(1, &quad_vertexbuffer);
	glDeleteVertexArrays(1, &VertexArrayID);

	// Close OpenGL window and terminate GLFW
	glfwTerminate();

	return 0;
}

Now there is only one thing that I want to do. Access to the pixels and modify them.

How Can I modify my code for to do that?