适用于OpenGL离屏渲染上下文的初始化代码

说明

最近做图像算法，需要用到shader对图像进行处理，用glut会有窗口，不适合写成UT测试用例，需要创建一个无窗口的OpenGL上下文。

代码

这部分代码其实是参考 Android的Skia 模块相关代码写的，适用于 Mac、EGL（Android）、X11（Ubuntu等Linux系统）平台。

h文件

class GLContext
{
public:
    class nativeContext;
    static nativeContext* init(int version=2);
    static void destroy(nativeContext* context);
};

class GLAutoContext
{
    public:
        GLAutoContext()
        {
            mContext = GLContext::init();
        }
        ~GLAutoContext()
        {
            GLContext::destroy(mContext);
        }
    private:
        GLContext::nativeContext* mContext;
};

cpp文件

#include "GL/GLContext.h"
#include <assert.h>

#ifdef GL_BUILD_FOR_ANDROID
#include <EGL/egl.h>
class GLContext::nativeContext { public: nativeContext() { gDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY); EGLint majorVersion; EGLint minorVersion; eglInitialize(gDisplay, &majorVersion, &minorVersion); EGLint numConfigs; static const EGLint configAttribs[] = { EGL_SURFACE_TYPE, EGL_PBUFFER_BIT, EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT, EGL_RED_SIZE, 8, EGL_GREEN_SIZE, 8, EGL_BLUE_SIZE, 8, EGL_ALPHA_SIZE, 8, EGL_NONE }; EGLConfig surfaceConfig; eglChooseConfig(gDisplay, configAttribs, &surfaceConfig, 1, &numConfigs); static const EGLint contextAttribs[] = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE }; gContext = eglCreateContext(gDisplay, surfaceConfig, NULL, contextAttribs); static const EGLint surfaceAttribs[] = { EGL_WIDTH, 1, EGL_HEIGHT, 1, EGL_NONE }; gSurface = eglCreatePbufferSurface(gDisplay, surfaceConfig, surfaceAttribs); eglMakeCurrent(gDisplay, gSurface, gSurface, gContext); } ~nativeContext() { eglMakeCurrent(gDisplay, EGL_NO_SURFACE , EGL_NO_SURFACE , EGL_NO_CONTEXT); eglDestroyContext(gDisplay, gContext); eglDestroySurface(gDisplay, gSurface); eglTerminate(gDisplay); gDisplay = EGL_NO_DISPLAY; } private: EGLContext gContext; EGLDisplay gDisplay; EGLSurface gSurface; }; #else #ifdef __APPLE__ #include <OpenGL/OpenGL.h> class GLContext::nativeContext { public: nativeContext() { CGLPixelFormatAttribute attributes[] = { kCGLPFADoubleBuffer, (CGLPixelFormatAttribute)0 }; CGLPixelFormatObj pixFormat; GLint npix; CGLChoosePixelFormat(attributes, &pixFormat, &npix); assert(NULL!=pixFormat); CGLCreateContext(pixFormat, NULL, &gContext); CGLReleasePixelFormat(pixFormat); assert(NULL!=gContext); CGLSetCurrentContext(gContext); } ~nativeContext() { CGLReleaseContext(gContext); } private: CGLContextObj gContext; }; #else #include <GL/glew.h> #include <GL/glut.h> #include <X11/Xlib.h> #include <GL/glx.h> class GLContext::nativeContext { public: nativeContext() { gDisplay = XOpenDisplay(0); int fbcount; static int visual_attribs[] = { GLX_X_RENDERABLE , True, GLX_DRAWABLE_TYPE , GLX_PIXMAP_BIT, None }; GLXFBConfig *fbc = glXChooseFBConfig(gDisplay, DefaultScreen(gDisplay), visual_attribs, &fbcount); int best_fbc = -1, best_num_samp = -1; int i; for (i = 0; i < fbcount; ++i) { XVisualInfo *vi = glXGetVisualFromFBConfig(gDisplay, fbc[i]); if (vi) { int samp_buf, samples; glXGetFBConfigAttrib(gDisplay, fbc[i], GLX_SAMPLE_BUFFERS, &samp_buf); glXGetFBConfigAttrib(gDisplay, fbc[i], GLX_SAMPLES, &samples); if (best_fbc < 0 || (samp_buf && samples > best_num_samp)) best_fbc = i, best_num_samp = samples; } XFree(vi); } GLXFBConfig bestFbc = fbc[best_fbc]; XFree(fbc); XVisualInfo *vi = glXGetVisualFromFBConfig(gDisplay, bestFbc); gPixmap = XCreatePixmap(gDisplay, RootWindow(gDisplay, vi->screen), 10, 10, vi->depth); gGlxPixmap = glXCreateGLXPixmap(gDisplay, vi, gPixmap); XFree(vi); gContext = glXCreateNewContext(gDisplay, bestFbc, GLX_RGBA_TYPE, 0, True); glXMakeCurrent(gDisplay, gGlxPixmap, gContext); glewInit(); } ~nativeContext() { glXMakeCurrent(gDisplay, 0,0); glXDestroyContext(gDisplay, gContext); glXDestroyGLXPixmap(gDisplay, gGlxPixmap); XFreePixmap(gDisplay, gPixmap); XCloseDisplay(gDisplay); gDisplay = NULL; } private: GLXContext gContext; Pixmap gPixmap; GLXPixmap gGlxPixmap; Display* gDisplay; }; #endif #endif GLContext::nativeContext* GLContext::init(int version) { return new nativeContext; } void GLContext::destroy(nativeContext* context) { delete context; }