opengl对图像进行模糊处理

右下角图片为模糊效果图

对图像进行模糊处理也就是平滑处理

图像模糊的用途：用来减少图像上的噪点或失真

同样需要对图像做卷积处理

卷积过程

卷积的数学表达式

本文的图像模糊采用的高斯滤波

具体操作：用一个卷积核扫描图像中的每一个像素,用模板确定的邻域内像素的加权

平均灰度值去替代模板中心像素点的值

opengl 中shader实现

varying vec2 V_Texcoord;

uniform sampler2D U_MainTexture;

void main()
{
	//高斯滤波核
	// 1 2 1
	// 2 4 2
	// 1 2 1
	vec4 color=vec4(0.0);
	int coreSize=3;
	float texelOffset=1/150.0;
	float kernel[9];

	kernel[6]=1;kernel[7]=2;kernel[8]=1;
	kernel[3]=2;kernel[4]=4;kernel[5]=2;
	kernel[0]=1;kernel[1]=2;kernel[2]=1;

	//移动高斯核,对原图做卷积计算
	int index=0;
	for(int y=0;y<coreSize;y++)
	{
		for(int x=0;x<coreSize;x++)
		{
		
			//原图像素点
			vec4 currentColor=texture2D(U_MainTexture,V_Texcoord+vec2((-1+x)*texelOffset,(-1+y)*texelOffset));
			//卷积计算
			color+=currentColor*kernel[index++];
		}
	}
	//根据邻域内像素的加权平均灰度值去替代模板中心像素点的值
	color/=16.0;
	gl_FragColor=color;
}

渲染入口

#include <windows.h>
#include "glew.h"
#include <stdio.h>
#include <math.h>
#include "utils.h"
#include "GPUProgram.h"
#include "ObjModel.h"
#include "FBO.h"
#include "FullScreenQuad.h"
#include "Glm/glm.hpp"
#include "Glm/ext.hpp"
#pragma comment(lib,"opengl32.lib")
#pragma comment(lib,"glew32.lib")

LRESULT CALLBACK GLWindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	switch (msg)
	{
	case WM_CLOSE:
		PostQuitMessage(0);
		break;
	}
	return DefWindowProc(hwnd,msg,wParam,lParam);
}


INT WINAPI WinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPSTR lpCmdLine, _In_ int nShowCmd)
{
	WNDCLASSEX wndClass;
	wndClass.cbClsExtra = 0;
	wndClass.cbSize = sizeof(WNDCLASSEX);
	wndClass.cbWndExtra = 0;
	wndClass.hbrBackground = NULL;
	wndClass.hCursor = LoadCursor(NULL,IDC_ARROW);
	wndClass.hIcon = NULL;
	wndClass.hIconSm = NULL;
	wndClass.hInstance = hInstance;
	wndClass.lpfnWndProc=GLWindowProc;
	wndClass.lpszClassName = L"OpenGL";
	wndClass.lpszMenuName = NULL;
	wndClass.style = CS_VREDRAW | CS_HREDRAW;
	ATOM atom = RegisterClassEx(&wndClass);

	RECT rect;
	rect.left = 0;
	rect.top = 0;
	rect.right = 1280;
	rect.bottom = 720;
	AdjustWindowRect(&rect, WS_OVERLAPPEDWINDOW, FALSE);
	HWND hwnd = CreateWindowEx(NULL, L"OpenGL", L"RenderWindow", WS_OVERLAPPEDWINDOW, 100, 100, rect.right-rect.left, rect.bottom-rect.top, NULL, NULL, hInstance, NULL);
	HDC dc = GetDC(hwnd);
	PIXELFORMATDESCRIPTOR pfd;
	memset(&pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
	pfd.nVersion = 1;
	pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_TYPE_RGBA | PFD_DOUBLEBUFFER;
	pfd.iLayerType = PFD_MAIN_PLANE;
	pfd.iPixelType = PFD_TYPE_RGBA;
	pfd.cColorBits = 32;
	pfd.cDepthBits = 24;
	pfd.cStencilBits = 8;

	int pixelFormatID = ChoosePixelFormat(dc, &pfd);

	SetPixelFormat(dc,pixelFormatID,&pfd);

	HGLRC rc = wglCreateContext(dc);
	wglMakeCurrent(dc, rc);
	GetClientRect(hwnd, &rect);
	int viewportWidth = rect.right - rect.left, viewportHeight = rect.bottom - rect.top;
	glewInit();

	GPUProgram originalProgram;
	originalProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/fullscreenquad.vs");
	originalProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/fullscreenquad.fs");
	originalProgram.Link();
	originalProgram.DetectAttribute("pos");
	originalProgram.DetectAttribute("texcoord");
	originalProgram.DetectUniform("U_MainTexture");

	GPUProgram erosionProgram;
	erosionProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/fullscreenquad.vs");
	erosionProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/Erosion.fs");
	erosionProgram.Link();
	erosionProgram.DetectAttribute("pos");
	erosionProgram.DetectAttribute("texcoord");
	erosionProgram.DetectUniform("U_MainTexture");

	GPUProgram dilationProgram;
	dilationProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/fullscreenquad.vs");
	dilationProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/Dilation.fs");
	dilationProgram.Link();
	dilationProgram.DetectAttribute("pos");
	dilationProgram.DetectAttribute("texcoord");
	dilationProgram.DetectUniform("U_MainTexture");

	GPUProgram gaussianProgram;
	gaussianProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/fullscreenquad.vs");
	gaussianProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/Gaussian.fs");
	gaussianProgram.Link();
	gaussianProgram.DetectAttribute("pos");
	gaussianProgram.DetectAttribute("texcoord");
	gaussianProgram.DetectUniform("U_MainTexture");

	GPUProgram gpuProgram;
	gpuProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/x_ray.vs");
	gpuProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/x_ray.fs");
	gpuProgram.Link();

	gpuProgram.DetectAttribute("pos");
	gpuProgram.DetectAttribute("texcoord");
	gpuProgram.DetectAttribute("normal");
	gpuProgram.DetectUniform("M");
	gpuProgram.DetectUniform("V");
	gpuProgram.DetectUniform("P");
	gpuProgram.DetectUniform("NM");
	gpuProgram.DetectUniform("U_EyePos");
	//init 3d model
	ObjModel cube,quad;
	cube.Init("Debug/res/model/Sphere.obj");
	//cube.Init("res/model/Quad.obj");

	float identity[] = {
		1.0f,0,0,0,
		0,1.0f,0,0,
		0,0,1.0f,0,
		0,0,0,1.0f
	};
	float eyePos[] = { -0.5f, 1.5f, -3.0f };

	glm::mat4 model1 = glm::translate<float>(-2.0f, 0.0f, -6.0f)*glm::rotate(-30.0f, 1.0f, 1.0f, 1.0f);
	glm::mat4 projectionMatrix = glm::perspective(50.0f, (float)viewportWidth / (float)viewportHeight, 0.1f, 1000.0f);
	glm::mat4 viewMatrix1 = glm::lookAt(glm::vec3(-0.5f, 1.5f, -3.0f), glm::vec3(-2.0f, 0.0f, -6.0f), glm::vec3(0.0f, 1.0f, 0.0f));

	glm::mat4 normalMatrix1 = glm::inverseTranspose(model1);

	FullScreenQuad fsq;
	fsq.Init();
	FBO fbo;
	fbo.AttachColorBuffer("color", GL_COLOR_ATTACHMENT0, GL_RGBA, viewportWidth, viewportHeight);
	fbo.AttachDepthBuffer("depth", viewportWidth, viewportHeight);
	fbo.Finish();

	GLuint mainTexture = CreateTextureFromFile("Debug/res/image/stone.bmp");
	ShowWindow(hwnd, SW_SHOW);
	UpdateWindow(hwnd);

	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

	glEnable(GL_DEPTH_TEST);
	MSG msg;
	while (true)
	{
		if (PeekMessage(&msg,NULL,NULL,NULL,PM_REMOVE))
		{
			if (msg.message==WM_QUIT)
			{
				break;
			}
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
		fbo.Bind();
		glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
		glEnable(GL_BLEND);
		glBlendFunc(GL_SRC_ALPHA, GL_ONE);
		glUseProgram(gpuProgram.mProgram);
		glUniformMatrix4fv(gpuProgram.GetLocation("P"), 1, GL_FALSE, glm::value_ptr(projectionMatrix));
		glUniform3fv(gpuProgram.GetLocation("U_EyePos"), 1, eyePos);
		glUniformMatrix4fv(gpuProgram.GetLocation("M"), 1, GL_FALSE, glm::value_ptr(model1));
		glUniformMatrix4fv(gpuProgram.GetLocation("V"), 1, GL_FALSE, glm::value_ptr(viewMatrix1));
		glUniformMatrix4fv(gpuProgram.GetLocation("NM"), 1, GL_FALSE, glm::value_ptr(normalMatrix1));
		cube.Bind(gpuProgram.GetLocation("pos"), gpuProgram.GetLocation("texcoord"), gpuProgram.GetLocation("normal"));
		cube.Draw();
		glDisable(GL_BLEND);
		fbo.Unbind();
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		glUseProgram(originalProgram.mProgram);
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, fbo.GetBuffer("color"));
		glUniform1i(originalProgram.GetLocation("U_MainTexture"), 0);
		fsq.DrawToLeftTop(originalProgram.GetLocation("pos"), originalProgram.GetLocation("texcoord"));

		glUseProgram(erosionProgram.mProgram);
		fsq.DrawToRightTop(erosionProgram.GetLocation("pos"), erosionProgram.GetLocation("texcoord"));

		glUseProgram(dilationProgram.mProgram);
		fsq.DrawToLeftBottom(dilationProgram.GetLocation("pos"), dilationProgram.GetLocation("texcoord"));

		glUseProgram(gaussianProgram.mProgram);
		glBindTexture(GL_TEXTURE_2D, mainTexture);
		glUniform1i(gaussianProgram.GetLocation("U_MainTexture"), 0);
		fsq.DrawToRightBottom(gaussianProgram.GetLocation("pos"), gaussianProgram.GetLocation("texcoord"));

		glFlush();
		SwapBuffers(dc);
	}
	return 0;
}