Android ImageReader.acquireLatestImage returns inv

Question

I am using Android ImageReader class to receive Bitmaps from MediaProjection.createVirtualDisplay method.

My code so far looks like this:

mProjection.createVirtualDisplay("test", width, height, density, flags, mImageReader.getSurface(), new VirtualDisplayCallback(), mHandler);
            mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
                @Override
                public void onImageAvailable(ImageReader reader) {
                    Image image = null;
                    try {
                        image = mImageReader.acquireLatestImage();
                        final Image.Plane[] planes = image.getPlanes();
                        final ByteBuffer buffer = planes[0].getBuffer();
                        final byte[] data = new byte[buffer.capacity()];
                        buffer.get(data);
                        final Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
                        if (bitmap==null)
                            Log.e(TAG, "bitmap is null");

                    } catch (Exception e) {
                        if (image!=null)
                            image.close();
                    }
                }

            }, mHandler);

The problem is that BitmapFactory cannot decode data[] back to Bitmap, i.e. BitmapFactory always returns null. The only messages I see from logcat come from android_media_ImageReader.cpp and go like this:

D/ImageReader_JNI(1432): ImageReader_imageSetup: Receiving JPEG in HAL_PIXEL_FORMAT_RGBA_8888 buffer.
W/ImageReader_JNI(1432): Image_getJpegSize: No JPEG header detected, defaulting to size=width=3891200

Image object returned by acquireLatestImage is not null but not a valid JPEG either, I tried to check with the following test which fails:

if((buf [0] & 0xFF) == 0xFF && (buf[1] & 0xFF) == 0xD8 && (buf[2] & 0xFF) == 0xFF && (buf[3] & 0xFF) == 0xE0)
    Log.e(TAG, "is JPG");
else
    Log.e(TAG, "not a valid JPG");

The only think I am suspecting at the moment is that Android 5.0 emulator I am testing against cannot hanlde the API calls.

Any ideas?

Answer 1

I encountered exactly your problem. My ImageReader created as so:

ImageReader.newInstance(mCaptureSize.getWidth(), mCaptureSize.getHeight(), ImageFormat.JPEG, 1);

The ImageReader above should only return compressed images, and these need to be decompressed. I acquireLatestImage(), then pass it through the following:

ByteBuffer bBuffer = planes[0].getBuffer;
bBuffer.rewind();
byte[] buffer = new byte[bBuffer.remaining()];
planes[0].getBuffer().get(buffer);
Bitmap bitmap = BitmapFactory.decodeByteArray(buffer, 0, buffer.length);

The key for me was to rewind the ByteBuffer. Your code should work as so:

mProjection.createVirtualDisplay("test", width, height, density, flags, mImageReader.getSurface(), new VirtualDisplayCallback(), mHandler);
            mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
                @Override
                public void onImageAvailable(ImageReader reader) {
                    Image image = null;
                    try {
                        image = mImageReader.acquireLatestImage();
                        final Image.Plane[] planes = image.getPlanes();
                        final ByteBuffer buffer = planes[0].getBuffer();
                        buffer.rewind()
                        final byte[] data = new byte[buffer.capacity()];
                        buffer.get(data);
                        final Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
                        if (bitmap==null)
                            Log.e(TAG, "bitmap is null");

                    } catch (Exception e) {
                        if (image!=null)
                            image.close();
                    }
                }

            }, mHandler);

I don't like having to copy the ByteBuffer through an intermediate byte[], but the internal array is protected.

Tested working on 5.0.1 on an HTC

Answer 2

I tried to use many example code. But none of those codes are working. I mixed those codes myself. And I created working sample code.

    final DisplayMetrics dm = getResources().getDisplayMetrics();
    mImageReader = ImageReader.newInstance(dm.widthPixels, dm.heightPixels, PixelFormat.RGBA_8888, 1);
    mProjection.createVirtualDisplay("screen-mirror", dm.widthPixels, dm.heightPixels, dm.densityDpi, DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR, mImageReader.getSurface(), vdCallback, mHandler);
    mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            Image image = reader.acquireLatestImage();
            if (image == null){
                return;
            }
            final Image.Plane[] planes = image.getPlanes();
            final ByteBuffer buffer = planes[0].getBuffer();
            int offset = 0;
            int pixelStride = planes[0].getPixelStride();
            int rowStride = planes[0].getRowStride();
            int rowPadding = rowStride - pixelStride * dm.widthPixels;
            // create bitmap
            Bitmap bitmap = Bitmap.createBitmap(dm.widthPixels+rowPadding/pixelStride, dm.heightPixels, Bitmap.Config.ARGB_8888);
            bitmap.copyPixelsFromBuffer(buffer);
            imageView.setImageBitmap(bitmap);
            image.close();
        }
    }, mHandler);

Answer 3

In case someone else stumbles on this, working code is as follows:

            mImageReader = ImageReader.newInstance(width, height, ImageFormat.JPEG, 5);
            mProjection.createVirtualDisplay("test", width, height, density, flags, mImageReader.getSurface(), new VirtualDisplayCallback(), mHandler);
            mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {

                @Override
                public void onImageAvailable(ImageReader reader) {
                    Image image = null;
                    FileOutputStream fos = null;
                    Bitmap bitmap = null;

                    try {
                        image = mImageReader.acquireLatestImage();
                        fos = new FileOutputStream(getFilesDir() + "/myscreen.jpg");
                        final Image.Plane[] planes = image.getPlanes();
                        final Buffer buffer = planes[0].getBuffer().rewind();
                        bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
                        bitmap.copyPixelsFromBuffer(buffer);
                        bitmap.compress(CompressFormat.JPEG, 100, fos);

                    } catch (Exception e) {
                        e.printStackTrace();

                        if (image!=null)
                            image.close();
                    } finally {
                        if (fos!=null) {
                            try {
                                fos.close();
                            } catch (IOException ioe) { 
                                ioe.printStackTrace();
                            }
                        }

                        if (bitmap!=null)
                            bitmap.recycle();
                    }
                }

            }, mHandler);

As you see I am saving the bitmap captured from ImageReader to a fileoutput stream and this produces a valid jpeg file.

The messages I was getting back from android_media_ImageReader.cpp were not indicating any sort of misbehaviour.

Hope it helps someone in the future!

Answer 4

I tested the code of the first answer, but unfortunately it does not work on real device. I make some investigation and the following code solved my problem:

 mImgReader = ImageReader.newInstance(mWidth, mHeight, PixelFormat.RGBA_8888, 5);
    mSurface = mImgReader.getSurface();// mSurfaceView.getHolder().getSurface();
    mImgReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            Log.i(TAG, "in OnImageAvailable");
            FileOutputStream fos = null;
            Bitmap bitmap = null;
            Image img = null;
            try {
                img = reader.acquireLatestImage();
                if (img != null) {
                    Image.Plane[] planes = img.getPlanes();
                    if (planes[0].getBuffer() == null) {
                        return;
                    }
                    int width = img.getWidth();
                    int height = img.getHeight();
                    int pixelStride = planes[0].getPixelStride();
                    int rowStride = planes[0].getRowStride();
                    int rowPadding = rowStride - pixelStride * width;
                    byte[] newData = new byte[width * height * 4];

                    int offset = 0;
                    bitmap = Bitmap.createBitmap(metrics,width, height, Bitmap.Config.ARGB_8888);
                    ByteBuffer buffer = planes[0].getBuffer();
                    for (int i = 0; i < height; ++i) {
                        for (int j = 0; j < width; ++j) {
                            int pixel = 0;
                            pixel |= (buffer.get(offset) & 0xff) << 16;     // R
                            pixel |= (buffer.get(offset + 1) & 0xff) << 8;  // G
                            pixel |= (buffer.get(offset + 2) & 0xff);       // B
                            pixel |= (buffer.get(offset + 3) & 0xff) << 24; // A
                            bitmap.setPixel(j, i, pixel);
                            offset += pixelStride;
                        }
                        offset += rowPadding;
                    }
                    String name = "/myscreen" + count + ".png";
                    count++;
                    File file = new File(Environment.getExternalStorageDirectory(), name);
                    fos = new FileOutputStream(file);
                    bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
                    Log.i(TAG, "image saved in" + Environment.getExternalStorageDirectory() + name);
                    img.close();
                }

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (null != fos) {
                    try {
                        fos.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if (null != bitmap) {
                    bitmap.recycle();
                }
                if (null != img) {
                    img.close();
                }

            }



        }
    }, mHandler);

Answer 5

The code in answer by @charlesjean works but I would rather not generate each pixel by my self. A better way to get the Image from ImageReader is just to create right sized bitmap and use the method copyPixelsFromBuffer(). Create ImageReader as follows:

mImageReader = ImageReader.newInstance(mWidth, mHeight, ImageFormat.RGB_565, 2);

Then you can get the image from mImageReader using the code below.

final Image.Plane[] planes = image.getPlanes();
final ByteBuffer buffer = planes[0].getBuffer();
int offset = 0;
int pixelStride = planes[0].getPixelStride();
int rowStride = planes[0].getRowStride();
int rowPadding = rowStride - pixelStride * mWidth;
// create bitmap
bitmap = Bitmap.createBitmap(mWidth+rowPadding/pixelStride, mHeight, Bitmap.Config.RGB_565);
bitmap.copyPixelsFromBuffer(buffer);
image.close();

I have described the process of capturing screen using MediaProjection API along with the mistakes most people made when getting image from ImageReader in a blog post which you can read if interested.