RxJava将字节数组转换为位图

Question

Sorry for my english. Now i learning rxJava 1 and try convert byte[] to Bitmap and set it to imageview. But it work slowly. Do i right work whith rxJava? ps: i chek and asynkTask work fater than rxJava, how it possible?

Observable.just(data)
                .map(new Func1<byte[], Bitmap>() {
                    @Override
                    public Bitmap call(byte[] bytes) {
                        BitmapFactory.Options options = new BitmapFactory.Options();
                        options.inJustDecodeBounds = false;
                        options.inPreferredConfig = Bitmap.Config.RGB_565;
                        options.inDither = true;
                        options.inMutable = true;

                        Bitmap largeBitmap = BitmapFactory.decodeByteArray(data, 0, data.length, options);
                        Bitmap bitmap = Bitmap.createScaledBitmap(largeBitmap
                                , (int) ((float) largeBitmap.getWidth() / 10)
                                , (int) ((float) largeBitmap.getHeight() / 10)
                                , true);

                        if (bitmap.getWidth() > bitmap.getHeight()) {
                            Matrix matrix = new Matrix();
                            matrix.postRotate(90); // anti-clockwise by 90 degrees

                            bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
                        }

                        float k = (float) bitmap.getWidth() / (float) w_target;

                        if (w_target < bitmap.getWidth()) {
                            bitmap = Bitmap.createScaledBitmap(bitmap, w_target, (int) ((float) bitmap.getHeight() / k), true);
                        }

                        return createBlackAndWhite(bitmap);
                    }
                })
                .observeOn(Schedulers.io())
                .subscribeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<Bitmap>() {
                    @Override
                    public void call(Bitmap bitmap) {
                        imageview.setImageBitmap(bitmap);
                    }
                }); 

Answer 1

Maybe you should change the Scheduler used to handle the process , instead of Schedulers.io() try Schedulers.computation() at least for some of your calcul.

According to the documentation

computation() : Creates and returns a Scheduler intended for computational work. This can be used for event-loops, processing callbacks and other computational work. Do not perform IO-bound work on this scheduler. Use Schedulers.io() instead.

io() : Creates and returns a Scheduler intended for IO-bound work. The implementation is backed by an Executor thread-pool that will grow as needed. This can be used for asynchronously performing blocking IO. Do not perform computational work on this scheduler. Use Schedulers.computation() instead.

Hope this helps.

Sorry for my english.

Answer 2

invert the schedulers to

.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())

the thread you observe on is the one in which imageView.setBitmap() will be called, subscribeOn on the other hand will set the thread for the bitmap manipulation