Android libwebp encoding

Question

Would anyone be able to provide an example of using the libwebp NDK library to encode an Image to webp ?

I'm trying to encode an image captured from the camera as RGB_565 using the code below:

@Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        int w = camera.getParameters().getPreviewSize().width;
        int h = camera.getParameters().getPreviewSize().height;
        try {
            int stride = (w + 1) & ~1;
            byte[] out = libwebp.WebPEncodeRGB(data, w, h, stride, 80f);
        } catch (Exception e) {
            e.printStackTrace();
        } 
    }

I've tried several values for stride, ranging from w, w+1, w*2, w*3 and w*4 ... the latter results in a fatal exception.

The above code produces a black and white image, that duplicates the picture several times all sideways...

Answer 1

I can't tell if WebP supports encoding from a RGB_565 stream, my guess is no.

As an alternative, you can convert it to RGB_888 such as in the answers given here: How does one convert 16-bit RGB565 to 24-bit RGB888?

And then the correct way to do stride is simply width*bytesPerPixel, or in the case of RGB_888 it would be width * 3. When encoding RGBA_8888 it would be width * 4.