从GLSurfaceView中拿到图片。

因为项目中视频拍摄使用第三方sdk，但是图片拍摄需要自己实现，而sdk的视频预览使用的是GLSurfaceview，SurfaceView 和 GLSurfaceView是自己独立渲染画面，不同于普通view。所以不能使用普通的view截图方式,在stackoverflow上找到的答案是这样的:

private Bitmap createBitmapFromGLSurface(int x, int y, int w, int h, GL10 gl)
            throws OutOfMemoryError {
        int bitmapBuffer[] = new int[w * h];
        int bitmapSource[] = new int[w * h];
        IntBuffer intBuffer = IntBuffer.wrap(bitmapBuffer);
        intBuffer.position(0);

        try {
            gl.glReadPixels(x, y, w, h, GL10.GL_RGBA, GL10.GL_UNSIGNED_BYTE, intBuffer);
            int offset1, offset2;
            for (int i = 0; i < h; i++) {
                offset1 = i * w;
                offset2 = (h - i - 1) * w;
                for (int j = 0; j < w; j++) {
                    int texturePixel = bitmapBuffer[offset1 + j];
                    int blue = (texturePixel >> 16) & 0xff;
                    int red = (texturePixel << 16) & 0x00ff0000;
                    int pixel = (texturePixel & 0xff00ff00) | red | blue;
                    bitmapSource[offset2 + j] = pixel;
                }
            }
        } catch (GLException e) {
            return null;
        }

        return Bitmap.createBitmap(bitmapSource, w, h, Bitmap.Config.ARGB_8888);
    }

其中如何使用这个方法如下：

private GLSurfaceView glSurfaceView; // findById() in onCreate
private Bitmap snapshotBitmap;

private interface BitmapReadyCallbacks {
    void onBitmapReady(Bitmap bitmap);
}

/* Usage code
   captureBitmap(new BitmapReadyCallbacks() {

        @Override
        public void onBitmapReady(Bitmap bitmap) {
            someImageView.setImageBitmap(bitmap);
        }
   });
*/

// supporting methods
private void captureBitmap(final BitmapReadyCallbacks bitmapReadyCallbacks) {
    glSurfaceView.queueEvent(new Runnable() {
        @Override
        public void run() {
            EGL10 egl = (EGL10) EGLContext.getEGL();
            GL10 gl = (GL10)egl.eglGetCurrentContext().getGL();
            snapshotBitmap = createBitmapFromGLSurface(0, 0, glSurfaceView.getWidth(), glSurfaceView.getHeight(), gl);

            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    bitmapReadyCallbacks.onBitmapReady(snapshotBitmap);
                }
            });

        }
    });

}

感谢：
https://stackoverflow.com/questions/5514149/capture-screen-of-glsurfaceview-to-bitmap
https://code.i-harness.com/en/q/5423a5