opengl实现图像亮度调整

效果图

1,取两幅图像的最大像素值合成新的图像

2,取两幅图像的最小像素值合成新的图像

实现shader

varying vec2 V_Texcoord;

uniform sampler2D U_BaseTexture;
uniform sampler2D U_BlendTexture;

void main()
{
	vec4 blendColor=texture2D(U_BlendTexture,V_Texcoord);
	vec4 baseColor=texture2D(U_BaseTexture,V_Texcoord);
	//颜色变亮
	gl_FragColor=max(blendColor,baseColor);
	//颜色变暗
	//gl_FragColor=min(blendColor,baseColor);

}

渲染入口

#include 
#include "glew.h"
#include 
#include 
#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")

FullScreenQuad fsq; 

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 = 800;
	rect.bottom = 600;
	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 combineProgram;
	combineProgram.AttachShader(GL_VERTEX_SHADER, "Debug/res/shader/fullscreenquad.vs");
	combineProgram.AttachShader(GL_FRAGMENT_SHADER, "Debug/res/shader/darker.fs");
	combineProgram.Link();
	combineProgram.DetectAttribute("pos");
	combineProgram.DetectAttribute("texcoord");
	combineProgram.DetectUniform("U_BaseTexture");//fbo -> color buffer
	combineProgram.DetectUniform("U_BlendTexture");//src -> color glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);



	//init 3d model
	ObjModel cube,quad,sphere;
	quad.Init("Debug/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
	};

	glm::mat4 quadModel = glm::translate(6.0f, 0.0f, -6.0f)*glm::rotate(-90.0f, 1.0f, 0.0f, 0.0f)*glm::scale(5.0f,5.0f,5.0f);
	glm::mat4 quadNormalMatrix = glm::inverseTranspose(quadModel);

	glm::mat4 projectionMatrix = glm::perspective(50.0f, (float)viewportWidth / (float)viewportHeight, 0.1f, 1000.0f);
	glm::mat4 viewMatrix3 = glm::lookAt(glm::vec3(14.0f, 2.5f, -10.0f), glm::vec3(6.0f, 1.0f, -6.0f), glm::vec3(0.0f, 1.0f, 0.0f));

	fsq.Init();


	GLuint head = CreateTextureFromFile("Debug/res/image/wood.bmp");
	GLuint grass = CreateTextureFromFile("Debug/res/image/earth.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);
		}
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		glEnable(GL_BLEND);
		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
		//normal rgba
		glUseProgram(originalProgram.mProgram);
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, head);
		glUniform1i(originalProgram.GetLocation("U_MainTexture"), 0);
		fsq.DrawToLeftTop(originalProgram.GetLocation("pos"), originalProgram.GetLocation("texcoord"));

		//hdr
		glUseProgram(originalProgram.mProgram);
		glBindTexture(GL_TEXTURE_2D,grass);
		glUniform1i(originalProgram.GetLocation("U_MainTexture"), 0);
		fsq.DrawToRightTop(originalProgram.GetLocation("pos"), originalProgram.GetLocation("texcoord"));

		//combine
		glUseProgram(combineProgram.mProgram);
		
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, head);//base image
		glUniform1i(combineProgram.GetLocation("U_BaseTexture"), 0);

		glActiveTexture(GL_TEXTURE1);
		glBindTexture(GL_TEXTURE_2D, grass);//blend image
		glUniform1i(combineProgram.GetLocation("U_BlendTexture"), 1);

		fsq.DrawToRightBottom(combineProgram.GetLocation("pos"), combineProgram.GetLocation("texcoord"));

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