如何使用片段着色器与图像

我正在尝试使用GLSL(橙皮书)执行简单的色彩校正操作。

我正在努力将着色器应用于图像。这是我的片段着色器来调整饱和度，从橙色的书偷来的。我不明白如何使用这个图像?

const vec3 lumCoeff = vec3(0.2125,0.7154,0.0721);
uniform float Alpha;
void main()
{
    vec3 intensity = vec3(dot(gl_Color.rgb, lumCoeff));
    vec3 color = mix(intensity, gl_color.rgb, Alpha);
    gl_FragColor = vec4(color, 1.0);
}

然后我的顶点着色器是

void main(void)
{
    gl_Position = ftransform();
}

我一直试图在使用OpenCv中读取图像，然后我使用glTexImage2d将其转换为纹理，但是，我不明白如何在OpenGL和c++中使用着色器。

何时以及如何将着色器应用于图像?

这是我要运行的代码。

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
//#include <GL/glew.h>
#include <GLUT/glut.h>
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#include "textfile.h"
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#define VIEWPORT_WIDTH              320 // 1280
#define VIEWPORT_HEIGHT             320 // 800
IplImage *Image;
static GLuint texName;
GLuint v,f,f2,p;
float lpos[4] = {1,0.5,1,0};
void changeSize(int w, int h) {
    // Prevent a divide by zero, when window is too short
    // (you cant make a window of zero width).
    if(h == 0)
        h = 1;
    float ratio = 1.0* w / h;
    // Reset the coordinate system before modifying
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    // Set the viewport to be the entire window
    glViewport(0, 0, w, h);
    // Set the correct perspective.
    gluPerspective(45,ratio,1,1000);
    glMatrixMode(GL_MODELVIEW);

}

void renderScene(void) {
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_FLAT);
    glEnable(GL_DEPTH_TEST);
    glGenTextures(1, &texName);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texName);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glPixelStorei (GL_UNPACK_ALIGNMENT,  Image->align);
    glPixelStorei (GL_UNPACK_ROW_LENGTH, Image->widthStep / Image->nChannels);
    glTexImage2D(GL_TEXTURE_2D, 0, 3, Image->width, Image->height, 0, GL_BGR, GL_UNSIGNED_BYTE, Image->imageData);
    glViewport(0, 0, VIEWPORT_WIDTH , VIEWPORT_HEIGHT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, VIEWPORT_WIDTH , 0, VIEWPORT_HEIGHT, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_TEXTURE_2D);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glBindTexture(GL_TEXTURE_2D, texName);
    glBegin(GL_QUADS);
    glTexCoord2f(0, 0); glVertex3f(0, 0, 0);
    glTexCoord2f(0, 1); glVertex3f(0, VIEWPORT_HEIGHT, 0);
    glTexCoord2f(1, 1); glVertex3f(VIEWPORT_WIDTH, VIEWPORT_HEIGHT, 0);
    glTexCoord2f(1, 0); glVertex3f(VIEWPORT_WIDTH, 0, 0);
    char *vs = NULL,*fs = NULL,*fs2 = NULL;
    v = glCreateShader(GL_VERTEX_SHADER);
    f = glCreateShader(GL_FRAGMENT_SHADER);
    //f2 = glCreateShader(GL_FRAGMENT_SHADER);

    vs = textFileRead("toon.vert");
    fs = textFileRead("toon.frag");
    //fs2 = textFileRead("toon2.frag");
    const char * ff = fs;
    //const char * ff2 = fs2;
    const char * vv = vs;
    glShaderSource(v, 1, &vv,NULL);
    glShaderSource(f, 1, &ff,NULL);
    //glShaderSource(f2, 1, &ff2,NULL);
    free(vs);free(fs);
    glCompileShader(v);
    glCompileShader(f);
    //glCompileShader(f2);
    p = glCreateProgram();
    glAttachShader(p,f);
    //glAttachShader(p,f2);
    glAttachShader(p,v);
    glLinkProgram(p);
    glUseProgram(p);
    glEnd();
    glFlush();
    glDisable(GL_TEXTURE_2D);
    // glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    // glLoadIdentity();
    // gluLookAt(0.0,0.0,5.0, 
    //        0.0,0.0,-1.0,
    //        0.0f,1.0f,0.0f);
    // glLightfv(GL_LIGHT0, GL_POSITION, lpos);
    // glutSolidTeapot(1);
    glutSwapBuffers();
}
void processNormalKeys(unsigned char key, int x, int y) {
    if (key == 27) 
        exit(0);
}

void setShaders() {
    char *vs = NULL,*fs = NULL,*fs2 = NULL;
    v = glCreateShader(GL_VERTEX_SHADER);
    f = glCreateShader(GL_FRAGMENT_SHADER);
    //f2 = glCreateShader(GL_FRAGMENT_SHADER);

    vs = textFileRead("toon.vert");
    fs = textFileRead("toon.frag");
    //fs2 = textFileRead("toon2.frag");
    const char * ff = fs;
    //const char * ff2 = fs2;
    const char * vv = vs;
    glShaderSource(v, 1, &vv,NULL);
    glShaderSource(f, 1, &ff,NULL);
    //glShaderSource(f2, 1, &ff2,NULL);
    free(vs);free(fs);
    glCompileShader(v);
    glCompileShader(f);
    //glCompileShader(f2);
    p = glCreateProgram();
    glAttachShader(p,f);
    //glAttachShader(p,f2);
    glAttachShader(p,v);
    glLinkProgram(p);
    glUseProgram(p);
}

int main(int argc, char **argv) {
    Image = cvLoadImage("lena.tiff",1);
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(100,100);
    glutInitWindowSize(320,320);
    glutCreateWindow("MM 2004-05");
    glutDisplayFunc(renderScene);
    glutIdleFunc(renderScene);
    glutReshapeFunc(changeSize);
    glutKeyboardFunc(processNormalKeys);
    glEnable(GL_DEPTH_TEST);
    glClearColor(1.0,1.0,1.0,1.0);
//  glEnable(GL_CULL_FACE);
    // glewInit();
    // if (glewIsSupported("GL_VERSION_2_0"))
    //  printf("Ready for OpenGL 2.0n");
    // else {
    //  printf("OpenGL 2.0 not supportedn");
    //  exit(1);
    // }
    //setShaders();
    glutMainLoop();
    // just for compatibiliy purposes
    return 0;
}

你没有传递任何统一采样器到你的着色器

你应该注意很多事情。

你不需要在渲染循环中转储所有初始化代码。你只是在扼杀你的程序。像这个纹理生成代码。它只需要执行一次。把它移到某个init()函数中。

glGenTextures(1, &texName);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texName);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glPixelStorei (GL_UNPACK_ALIGNMENT,  Image->align);
glPixelStorei (GL_UNPACK_ROW_LENGTH, Image->widthStep / Image->nChannels);
glTexImage2D(GL_TEXTURE_2D, 0, 3, Image->width, Image->height, 0, GL_BGR, GL_UNSIGNED_BYTE, Image->imageData);

然后这个着色器程序的创建，编译和链接这通常在应用程序启动时完成，只有一次。之后，你可以在渲染循环中调用glUseProgram(handle)。

char *vs = NULL,*fs = NULL,*fs2 = NULL;
v = glCreateShader(GL_VERTEX_SHADER);
f = glCreateShader(GL_FRAGMENT_SHADER);
//f2 = glCreateShader(GL_FRAGMENT_SHADER);

vs = textFileRead("toon.vert");
fs = textFileRead("toon.frag");
//fs2 = textFileRead("toon2.frag");
const char * ff = fs;
//const char * ff2 = fs2;
const char * vv = vs;
glShaderSource(v, 1, &vv,NULL);
glShaderSource(f, 1, &ff,NULL);
//glShaderSource(f2, 1, &ff2,NULL);
free(vs);free(fs);
glCompileShader(v);
glCompileShader(f);
//glCompileShader(f2);
p = glCreateProgram();
glAttachShader(p,f);
//glAttachShader(p,f2);
glAttachShader(p,v);
glLinkProgram(p);

在着色器初始化时检查错误是很重要的。遵循这些优秀的教程来了解如何做到这一点。
你需要将使用OpenCV创建的纹理作为统一变量传递给着色器。看这里知道什么是均匀变量。

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