Update Backpressure.md

Fixes Backpressure.md on ReactiveX#6132 

Fix Images on Backpressure.md crashed on wrong address. Put full address of images.

Author: maryang710

docs/Backpressure.md

@@ -20,7 +20,7 @@ Cold Observables are ideal for the reactive pull model of backpressure described
 
 Your first line of defense against the problems of over-producing Observables is to use some of the ordinary set of Observable operators to reduce the number of emitted items to a more manageable number. The examples in this section will show how you might use such operators to handle a bursty Observable like the one illustrated in the following marble diagram:
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.bursty.png" width="640" height="35" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.bursty.png" width="640" height="35" />​
 
 By fine-tuning the parameters to these operators you can ensure that a slow-consuming observer is not overwhelmed by a fast-producing Observable.
 
@@ -33,23 +33,23 @@ The following diagrams show how you could use each of these operators on the bur
 ### sample (or throttleLast)
 The `sample` operator periodically "dips" into the sequence and emits only the most recently emitted item during each dip:
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.sample.png" width="640" height="260" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.sample.png" width="640" height="260" />​
 ````groovy
 Observable<Integer> burstySampled = bursty.sample(500, TimeUnit.MILLISECONDS);
 ````
 
 ### throttleFirst
 The `throttleFirst` operator is similar, but emits not the most recently emitted item, but the first item that was emitted after the previous "dip":
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.throttleFirst.png" width="640" height="260" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.throttleFirst.png" width="640" height="260" />​
 ````groovy
 Observable<Integer> burstyThrottled = bursty.throttleFirst(500, TimeUnit.MILLISECONDS);
 ````
 
 ### debounce (or throttleWithTimeout)
 The `debounce` operator emits only those items from the source Observable that are not followed by another item within a specified duration:
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.debounce.png" width="640" height="240" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.debounce.png" width="640" height="240" />​
 ````groovy
 Observable<Integer> burstyDebounced = bursty.debounce(10, TimeUnit.MILLISECONDS);
 ````
@@ -64,14 +64,14 @@ The following diagrams show how you could use each of these operators on the bur
 
 You could, for example, close and emit a buffer of items from the bursty Observable periodically, at a regular interval of time:
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.buffer2.png" width="640" height="270" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.buffer2.png" width="640" height="270" />​
 ````groovy
 Observable<List<Integer>> burstyBuffered = bursty.buffer(500, TimeUnit.MILLISECONDS);
 ````
 
 Or you could get fancy, and collect items in buffers during the bursty periods and emit them at the end of each burst, by using the `debounce` operator to emit a buffer closing indicator to the `buffer` operator:
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.buffer1.png" width="640" height="500" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.buffer1.png" width="640" height="500" />​
 ````groovy
 // we have to multicast the original bursty Observable so we can use it
 // both as our source and as the source for our buffer closing selector:
@@ -86,14 +86,14 @@ Observable<List<Integer>> burstyBuffered = burstyMulticast.buffer(burstyDebounce
 
 `window` is similar to `buffer`. One variant of `window` allows you to periodically emit Observable windows of items at a regular interval of time:
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.window1.png" width="640" height="325" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.window1.png" width="640" height="325" />​
 ````groovy
 Observable<Observable<Integer>> burstyWindowed = bursty.window(500, TimeUnit.MILLISECONDS);
 ````
 
 You could also choose to emit a new window each time you have collected a particular number of items from the source Observable:
 
-<img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.window2.png" width="640" height="325" />​
+<img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.window2.png" width="640" height="325" />​
 ````groovy
 Observable<Observable<Integer>> burstyWindowed = bursty.window(5);
 ````
@@ -158,11 +158,11 @@ For this to work, though, Observables _A_ and _B_ must respond correctly to the
 
 <dl>
  <dt><tt>onBackpressureBuffer</tt></dt>
-  <dd>maintains a buffer of all emissions from the source Observable and emits them to downstream Subscribers according to the <tt>request</tt>s they generate<br /><img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.obp.buffer.png" width="640" height="300" /><br />an experimental version of this operator (not available in RxJava 1.0) allows you to set the capacity of the buffer; applying this operator will cause the resulting Observable to terminate with an error if this buffer is overrun​</dd>
+  <dd>maintains a buffer of all emissions from the source Observable and emits them to downstream Subscribers according to the <tt>request</tt>s they generate<br /><img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.obp.buffer.png" width="640" height="300" /><br />an experimental version of this operator (not available in RxJava 1.0) allows you to set the capacity of the buffer; applying this operator will cause the resulting Observable to terminate with an error if this buffer is overrun​</dd>
  <dt><tt>onBackpressureDrop</tt></dt>
-  <dd>drops emissions from the source Observable unless there is a pending <tt>request</tt> from a downstream Subscriber, in which case it will emit enough items to fulfill the request<br /><img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.obp.drop.png" width="640" height="245" />​</dd>
+  <dd>drops emissions from the source Observable unless there is a pending <tt>request</tt> from a downstream Subscriber, in which case it will emit enough items to fulfill the request<br /><img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.obp.drop.png" width="640" height="245" />​</dd>
  <dt><tt>onBackpressureBlock</tt> <em style="color: #f00;">(experimental, not in RxJava 1.0)</em></dt>
-  <dd>blocks the thread on which the source Observable is operating until such time as a Subscriber issues a <tt>request</tt> for items, and then unblocks the thread only so long as there are pending requests<br /><img src="/ReactiveX/RxJava/wiki/images/rx-operators/bp.obp.block.png" width="640" height="245" /></dd>
+  <dd>blocks the thread on which the source Observable is operating until such time as a Subscriber issues a <tt>request</tt> for items, and then unblocks the thread only so long as there are pending requests<br /><img src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/bp.obp.block.png" width="640" height="245" /></dd>
 </dl>
 
 If you do not apply any of these operators to an Observable that does not support backpressure, _and_ if either you as the Subscriber or some operator between you and the Observable attempts to apply reactive pull backpressure, you will encounter a `MissingBackpressureException` which you will be notified of via your `onError()` callback.
@@ -172,4 +172,4 @@ If you do not apply any of these operators to an Observable that does not suppor
 If the standard operators are providing the expected behavior, [one can write custom operators in RxJava](https://github.com/ReactiveX/RxJava/wiki/Implementing-custom-operators-(draft)).
 
 # See also
-* [RxJava 0.20.0-RC1 release notes](https://github.com/ReactiveX/RxJava/releases/tag/0.20.0-RC1)
+* [RxJava 0.20.0-RC1 release notes](https://github.com/ReactiveX/RxJava/releases/tag/0.20.0-RC1)