android egl 代码,android jni 用c++使用opengles和egl实现离屏渲染

最近在做视频有关的东西,用开源的ffmpeg解码视频,在通过opengl渲染出来,因为有使用到egl就试了试离屏渲染

EGLConfig eglConf;

EGLSurface eglSurface;

EGLContext eglCtx;

EGLDisplay eglDisp;

egl用到的就是这四个

先初始化

EGLint configSpec[] = { EGL_RED_SIZE, 8,

EGL_GREEN_SIZE, 8,

EGL_BLUE_SIZE, 8,

EGL_SURFACE_TYPE, EGL_WINDOW_BIT, EGL_NONE };

EGLint surfaceAttr[] = {

EGL_WIDTH, width,

EGL_HEIGHT, height,

EGL_NONE

};

eglDisp = eglGetDisplay(EGL_DEFAULT_DISPLAY);

EGLint eglMajVers, eglMinVers;

EGLint numConfigs;

eglInitialize(eglDisp, &eglMajVers, &eglMinVers);

eglChooseConfig(eglDisp, configSpec, &eglConf, 1, &numConfigs);

eglSurface = eglCreatePbufferSurface(eglDisp, eglConf, surfaceAttr);

const EGLint ctxAttr[] = {

EGL_CONTEXT_CLIENT_VERSION, 2,

EGL_NONE

};

eglCtx = eglCreateContext(eglDisp, eglConf,EGL_NO_CONTEXT, ctxAttr);

上边的width和height是模拟窗口的宽高 最好和图片的比例一致,不然转成图片会拉伸

eglMakeCurrent(eglDisp, eglSurface, eglSurface, eglCtx);

设置显示的窗口，前一个窗口是显示窗口，后一个是写入窗口，通过调用这个来切换窗口

然后可以用opengl 进行画图了

画完后调用一下

eglSwapBuffers(eglDisp, eglSurface);

把东西显示在窗口上

最后加个释放

eglMakeCurrent(eglDisp, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);

eglDestroyContext(eglDisp, eglCtx);

eglDestroySurface(eglDisp, eglSurface);

eglTerminate(eglDisp);

eglDisp = EGL_NO_DISPLAY;

eglSurface = EGL_NO_SURFACE;

eglCtx = EGL_NO_CONTEXT;

试了试双屏切换

glViewport(0, 0, w, h);

glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

eglSwapBuffers(eglDisp, eglSurface);

jclass jcl = env->GetObjectClass(ob);

jmethodID mid = env->GetMethodID(jcl, "getBitmap", "(II)V");

env->CallVoidMethod(ob, mid,w,h);

第一次是离屏渲染，渲染完成后调用java代码把图片显示出来

public void getBitmap(int width,int height){

IntBuffer RGBABuffer = IntBuffer.allocate(width * height);

RGBABuffer.position(0);

GLES20.glReadPixels(0, 0, width, height,GLES20.GL_RGBA,GLES20.GL_UNSIGNED_BYTE,RGBABuffer);

int[] pixls = RGBABuffer.array();

for (int y = 0; y < height / 2; y++) {

for (int x = 0; x < width; x++) {

int pos1 = y * width + x;

int pos2 = (height - 1 - y) * width + x;

int tmp = pixls[pos1];

pixls[pos1] = (pixls[pos2] & 0xFF00FF00) | ((pixls[pos2] >> 16) & 0xff) | ((pixls[pos2] << 16) & 0x00ff0000); // ABGR->ARGB

pixls[pos2] = (tmp & 0xFF00FF00) | ((tmp >> 16) & 0xff) | ((tmp << 16) & 0x00ff0000);

}

}

if (height % 2 == 1) { // 中间一行

for (int x = 0; x < width; x++) {

int pos = (height / 2 + 1) * width + x;

pixls[pos] = (pixls[pos] & 0xFF00FF00) | ((pixls[pos] >> 16) & 0xff) | ((pixls[pos] << 16) & 0x00ff0000);

}

}

final Bitmap modelBitmap = Bitmap.createBitmap(pixls, width, height, Bitmap.Config.ARGB_8888);

runOnUiThread(new Runnable() {

@Override

public void run() {

ImageView imageView = (ImageView) findViewById(R.id.iv_opengl);

imageView.setImageBitmap(modelBitmap);

}

});

}

然后切换

eglMakeCurrent(eglDisp, eglWindow, eglSurface, eglCtx);

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glViewport(left, top, viewWidth, viewHeight);

glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

eglSwapBuffers(eglDisp, eglWindow);

切换的时候要再先清屏在画，不然两个纹理会重叠