Capture screen of GLSurfaceView to bitmap

Question

I need to be able to capture an image of a GLSurfaceView at certain moment in time. I have the following code:

relative.setDrawingCacheEnabled(true);
screenshot = Bitmap.createBitmap(relative.getDrawingCache());
relative.setDrawingCacheEnabled(false);
Log.v(TAG, "Screenshot height: " + screenshot.getHeight());
image.setImageBitmap(screenshot); 

The GLSurfaceView is contained within a RelativeLayout, but I have also tries it straight using the GLSurfaceView to try and capture the image. With this I think the screen captures a transparent image, i.e. nothing there. Any help will be appreciated.

Answer 1

SurfaceView and GLSurfaceView punch holes in their windows to allow their surfaces to be displayed. In other words, they have transparent areas.

So you cannot capture an image by calling GLSurfaceView.getDrawingCache().

If you want to get an image from GLSurfaceView, you should invoke gl.glReadPixels() in GLSurfaceView.onDrawFrame().

I patched createBitmapFromGLSurface method and call it in onDrawFrame().

(The original code might be from skuld's code.)

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);
}