opengl对图像进行腐蚀和膨胀

效果图

膨胀的原理:

膨胀就是求局部最大值的操作,就是给定一个核对图像进行卷积操作，见下图

将核B与图像A卷积,即计算B覆盖区域的像素点的最大值，并把这个最大值赋给参考点指定的像素,这样

就会使图像中的高亮区域逐渐增长,这就是膨胀的效果,膨胀的数学表达式

opengl中膨胀效果的shader实现

varying vec2 V_Texcoord;
uniform sampler2D U_MainTexture;void main()
{vec4 maxValue=vec4(0.0);int coreSize=3;//卷积核的尺寸  3x3int halfCoreSize=coreSize/2;float texelOffset=1/100.0;//纹理坐标偏移量for(int y=0;y<coreSize;y++){for(int x=0;x<coreSize;x++){//计算卷积核覆盖区域像素点的最大值vec4 color=texture2D(U_MainTexture,V_Texcoord+vec2((-halfCoreSize+x)*texelOffset,(-halfCoreSize+y)*texelOffset));maxValue=max(maxValue,color);}}gl_FragColor=maxValue;}

腐蚀的原理:

腐蚀和膨胀相反，就局部最小值,腐蚀示意图

腐蚀的数学表达式

opengl中腐蚀的shader实现

varying vec2 V_Texcoord;uniform sampler2D U_MainTexture;void main()
{vec4 minValue=vec4(1.0);int coreSize=6;int halfCoreSize=coreSize/2;float texelOffset=1/100.0;//遍历核for(int y=0;y<coreSize;y++){for(int x=0;x<coreSize;x++){//计算核B覆盖区域的像素点的最小值vec4 currentAlpha=texture2D(U_MainTexture,V_Texcoord+vec2((-halfCoreSize+x)*texelOffset,(-halfCoreSize+y)*texelOffset));minValue=min(minValue,currentAlpha);}}gl_FragColor=minValue;
}

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 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();   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);
        }
        //将球模型绘制到fbo
        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();       //将fbo里面已经绘制好的球模型作为纹理 贴到不同位置的四边形上用glUseProgram切换shader实现不同的效果
        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"));      glBindTexture(GL_TEXTURE_2D, 0);
        glFlush();
        SwapBuffers(dc);
    }
    return 0;
}

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