bitmap - Android ImageReader.acquireLatestImage returns invalid JPG

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

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.