OpenGL (ES） 图像处理C++

我目前正在尝试使用OpenGL ES进行图像处理。我正在尝试做一些基本的图像效果，比如模糊切换色彩空间等。 我想构建最简单的程序来执行以下操作：

• 图像加载
• 图像处理(使用着色器(
• 图像保存

我已经设法构建了以下设置：

• 一个 OpenGL 上下文
• 我想在使用 DevIL 加载时执行效果的图像。
两个着色器
• (一个顶点着色器和一个片段着色器(

我现在只能使用我加载的图像将数据发送到片段着色器。我正在尝试做的是将图像作为sampler2D发送到片段着色器并对其应用处理。

我有多个问题，例如：

• 如果我想做的只是纯 2D 图像处理，我是否需要顶点着色器？
如果我这样做，应该在这个顶点
• 着色器中做什么，因为我根本没有顶点。我应该创建四边形顶点(如 (0,0( (1， 0( (0， 1( (1， 1(( ？如果是这样，为什么？
• 我是否需要使用 VBO(似乎与顶点着色器有关(、FBO 或其他类似的东西？
我
• 不能只将图像加载到纹理中并等待片段着色器在此纹理上执行我想要的所有操作吗？
• 有人可以提供一些简单的"干净"代码来帮助我理解(没有任何花哨的类使理解如此复杂(？

以下是我的片段着色器在简单颜色交换中的样子：

uniform int width;
uniform int height;
uniform sampler2D texture;
void main() {
vec2 texcoord = vec2(gl_FragCoord.x/width, gl_FragCoord.y/height);
vec4 texture_value = texture2D(texture, texcoord);
gl_FragColor = texture_value.bgra;
}

和我的主要.cpp：

int main(int argc, char** argv)
{
if (argc != 4) {
std::cerr << "Usage: " << argv[0] << " <vertex shader path> <fragment shader path> <image path>" << std::endl;
return EXIT_FAILURE;
}
// Get an EGL valid display
EGLDisplay display;
display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
if (display == EGL_NO_DISPLAY) {
std::cerr << "Failed to get EGL Display" << std::endl
<< "Error: " << eglGetError() << std::endl;
return EXIT_FAILURE;
}
else {
std::cerr << "Successfully get EGL Display." << std::endl;
}

// Create a connection to the display
int minor, major;
if (eglInitialize(display, &minor, &major) == EGL_FALSE) {
std::cerr << "Failed to initialize EGL Display" << std::endl
<< "Error: " << eglGetError() << std::endl;
eglTerminate(display);
return EXIT_FAILURE;
}
else {
std::cerr << "Successfully intialized display (OpenGL ES version " << minor << "." << major << ")." << std::endl;
}
// OpenGL ES Config are used to specify things like multi sampling, channel size, stencil buffer usage, & more
// See the doc: https://www.khronos.org/registry/EGL/sdk/docs/man/html/eglChooseConfig.xhtml for more informations
EGLConfig config;
EGLint num_configs; 
if (!eglChooseConfig(display, configAttribs, &config, 1, &num_configs)) {
std::cerr << "Failed to choose EGL Config" << std::endl
<< "Error: " << eglGetError() << std::endl;
eglTerminate(display);
return EXIT_FAILURE;
}
else {
std::cerr << "Successfully choose OpenGL ES Config ("<< num_configs << ")." << std::endl;
}
// Creating an OpenGL Render Surface with surface attributes defined above.
EGLSurface surface = eglCreatePbufferSurface(display, config, pbufferAttribs);
if (surface == EGL_NO_SURFACE) {
std::cerr << "Failed to create EGL Surface." << std::endl
<< "Error: " << eglGetError() << std::endl;
}
else {
std::cerr << "Successfully created OpenGL ES Surface." << std::endl;
}
eglBindAPI(EGL_OPENGL_API);
EGLContext context = eglCreateContext(display, config, EGL_NO_CONTEXT, contextAttribs);
if (context == EGL_NO_CONTEXT) {
std::cerr << "Failed to create EGL Context." << std::endl
<< "Error: " << eglGetError() << std::endl;
}
else {
std::cerr << "Successfully created OpenGL ES Context." << std::endl;
}
//Bind context to surface
eglMakeCurrent(display, surface, surface, context);
// Create viewport and check if it has been created correctly
glViewport(0, 0, WIDTH, HEIGHT);
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
if (viewport[2] != WIDTH || viewport[3] != HEIGHT) {
std::cerr << "Failed to create the viewport. Size does not match (glViewport/glGetIntegerv not working)." << std::endl
<< "OpenGL ES might be faulty!" << std::endl
<< "If you are on Raspberry Pi, you should not updated EGL as it will install fake EGL." << std::endl;
eglTerminate(display);
return EXIT_FAILURE;
}
// Clear buffer and get ready to draw some things
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Create a shader program
GLuint program = load_shaders(std::string(argv[1]), std::string(argv[2]));
if (program == -1)
{
std::cerr << "Failed to create a shader program. See above for more details." << std::endl;
eglTerminate(display);
return EXIT_FAILURE;
}
/* Initialization of DevIL */
if (ilGetInteger(IL_VERSION_NUM) < IL_VERSION) {
std::cerr << "Failed to use DevIL: Wrong version." << std::endl;
return EXIT_FAILURE;
}
ilInit(); 
ILuint image = load_image(argv[3]);
GLuint texId;
glGenTextures(1, &texId); /* Texture name generation */
glBindTexture(GL_TEXTURE_2D, texId); /* Binding of texture name */
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); /* We will use linear interpolation for magnification filter */
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); /* We will use linear interpolation for minifying filter */
glTexImage2D(GL_TEXTURE_2D, 0, ilGetInteger(IL_IMAGE_BPP), ilGetInteger(IL_IMAGE_WIDTH), ilGetInteger(IL_IMAGE_HEIGHT), 
0, ilGetInteger(IL_IMAGE_FORMAT), GL_UNSIGNED_BYTE, ilGetData()); /* Texture specification */

谢谢。