Capture rendered image from OpenGL in Android and save it to a JPEG

Question

I have a problem with saving a rendered image to my gallery as a jpeg file. I'm applying a photo effect from the android EffectFactory an render it on a glSurfaceView. Since now i#ve managed to take a screenshot of the image from my glSurfaceView. The problem is that i don't want to take just a screenshot because then the image looses much of its original size and quality because when the original image is e.g. 1944 × 2592 but the device screen is only 768 × 1038 in my case its not the original anymore. The other problem is that when i take a screenshot i have also the black parts of my glSurfacView where the image isn't displayed on my saved image because the image doens't fill the whole glSurfaceView in many cases. Since now i tried it with this 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);
}

Can anyone please tell me how i get a bitmap/jpeg from the rendered image in the original size of the image? Is it even possible with gl.glReadPixels?? Or can i get the image directly from a framebuffer somehow? Its important that i can get the image in its original size.

Hi user2212391 , did you work this out, I'm looking at the exact same problem at the moment. Thanks. — user1540142, Mar 01 '14 at 06:24
@Nicol and user2212391 have you found of this problem?? If yes, please tell me here or email me at robinroyal15@gmail.com — Robin Royal, Dec 26 '14 at 16:14

score 2 · Answer 1 · answered Jun 10 '17 at 16:58

    public static Bitmap createBitmap(int width,int height){

//   int width=bitmap.getWidth();
//   int height =bitmap.getHeight();
            int screenshotSize = width * height;
            ByteBuffer bb = ByteBuffer.allocateDirect(screenshotSize * 4);
            bb.order(ByteOrder.nativeOrder());
            GLES20.glReadPixels(5, 0, width, height, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, bb);
            int pixelsBuffer[] = new int[screenshotSize];
            bb.asIntBuffer().get(pixelsBuffer);
            bb = null;
            Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
            bitmap.setPixels(pixelsBuffer, screenshotSize-width, -width,0, 0, width, height);
            pixelsBuffer = null;

            short sBuffer[] = new short[screenshotSize];
            ShortBuffer sb = ShortBuffer.wrap(sBuffer);
            bitmap.copyPixelsToBuffer(sb);

            //Making created bitmap (from OpenGL points) compatible with Android bitmap
            for (int i = 0; i < screenshotSize; ++i) {
                short v = sBuffer[i];
                sBuffer[i] = (short) (((v&0x1f) << 11) | (v&0x7e0) | ((v&0xf800) >> 11));
            }
            sb.rewind();
            bitmap.copyPixelsFromBuffer(sb);
//            if(savepicture!=null){
//                savepicture.onPictureSaved(bitmap);
//                // new SaveTask(bitmap, FileUtils.getFileDir().getPath(),"IMG"+System.currentTimeMillis()+".png", savepicture).execute();
//                screenshot = false;
//            }

            return bitmap;
    }

Capture rendered image from OpenGL in Android and save it to a JPEG

1 Answers1