How to use RenderScript to convert YUV_420_888 YUV Image to Bitmap | Minhaz’s Blog

[utterances-bot]

How to use RenderScript to convert YUV_420_888 YUV Image to Bitmap | Minhaz’s Blog

RenderScript turns out to be one of the best APIs for running computationally-intensive code on the CPU or GPU (that too, without having to make use of the NDK or GPU-specific APIs). We can use some existing intrinsics or create our new kernels that describe the computation and the framework takes care of scheduling & execution. In this code I have explained how to useScriptIntrinsicYuvToRGB intrinsic that is available in Android APIs to convert an android.media.Image in YUV_420_888 format to Bitmap.

https://blog.minhazav.dev/how-to-use-renderscript-to-convert-YUV_420_888-yuv-image-to-bitmap/

[dburckh]

Good stuff, I'm trying to use the output of ExoPlayer to create JPEG/WEBP thumbs. It's a similar problem.

If you only need Q+, you can convert to Bitmap instantly. Further, if you convert to RGBA you can use Bitmap.compress() to output any supported format.

Notes:

• The "hardware" bitmap will display as is.
• You have to convert to a Hardware RGBA Bitmap to get Bitmap.compress() to work. It won't work on YUV_420. :(

Tested on Pixel 3a, Android S. toRGBA, 5-7 ms, toJPEG=32-40ms

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
    long start = SystemClock.uptimeMillis();
    HardwareBuffer hardwareBuffer = image.getHardwareBuffer();
    final Bitmap hardware = Bitmap.wrapHardwareBuffer(hardwareBuffer, null);
    final ImageReader rgbaImageReader = ImageReader.newInstance(hardware.getWidth(),
         hardware.getHeight(), PixelFormat.RGBA_8888, 1, 
         HardwareBuffer.USAGE_GPU_SAMPLED_IMAGE);
    final Surface surface = rgbaImageReader.getSurface();
    final Canvas canvas = surface.lockHardwareCanvas();
    canvas.drawBitmap(hardware, 0f, 0f, null);
    surface.unlockCanvasAndPost(canvas);
    rgbaImageReader.setOnImageAvailableListener(reader -> {
        final Image rgbaImage = rgbaImageReader.acquireNextImage();
        final Bitmap rgb = Bitmap.wrapHardwareBuffer(rgbaImage.getHardwareBuffer(), null);
        Log.d("TAG", "toRGBA ms=" + (SystemClock.uptimeMillis() - start));
        final ByteArrayOutputStream out = new ByteArrayOutputStream();
        rgb.compress(Bitmap.CompressFormat.JPEG, 90, out);
        Log.d("TAG", "toJPEG ms=" + (SystemClock.uptimeMillis() - start));
    }, mImageView.getHandler());
}

[dburckh]

That was with a 720p image. Numbers at 8MP (3264x2448). toRGBA=15ms, toJPEG=(180-15)=165. Still crushing it on the toRGBA side. I would like to avoid C++, so I'm thinking about using a hybrid RenderScript/Bitmap.wrapBuffer() approach.