Fix ScrollView Snapshots

#34

1.evaluated the real height when the isScrollView is true
2.upgrade README.md

README.md

     - `"base64"`: encode as base64 and returns the raw string. Use only with small images as this may result of lags (the string is sent over the bridge). *N.B. This is not a data uri, use `data-uri` instead*.
     - `"data-uri"`: same as `base64` but also includes the [Data URI scheme](https://en.wikipedia.org/wiki/Data_URI_scheme) header.
  - **`filename`** *(string)*: the name of the generated file if any (Android only). Defaults to `ReactNative_snapshot_image_${timestamp}`.
+ - **`isScrollView`** *(bool)*: View is evaluated the real height when the value is true.
 
 ## Caveats
 

android/src/main/java/fr/greweb/reactnativeviewshot/RNViewShotModule.java

         Integer width = options.hasKey("width") ? (int)(displayMetrics.density * options.getDouble("width")) : null;
         Integer height = options.hasKey("height") ? (int)(displayMetrics.density * options.getDouble("height")) : null;
         String result = options.hasKey("result") ? options.getString("result") : "file";
+        Boolean isScrollView = options.hasKey("isScrollView") ? options.getBoolean("isScrollView"):false;
         try {
             String name = options.hasKey("filename") ? options.getString("filename") : null;
             File tmpFile = "file".equals(result) ? createTempFile(getReactApplicationContext(), format, name) : null;
             UIManagerModule uiManager = this.reactContext.getNativeModule(UIManagerModule.class);
-            uiManager.addUIBlock(new ViewShot(tag, format, compressFormat, quality, width, height, tmpFile, result, promise));
+            uiManager.addUIBlock(new ViewShot(tag, format, compressFormat, quality, width, height, tmpFile, result,isScrollView,promise));
         }
         catch (Exception e) {
             promise.reject(ViewShot.ERROR_UNABLE_TO_SNAPSHOT, "Failed to snapshot view tag "+tag);

android/src/main/java/fr/greweb/reactnativeviewshot/ViewShot.java

 package fr.greweb.reactnativeviewshot;
 
 import javax.annotation.Nullable;
+
+import android.app.Activity;
 import android.graphics.Bitmap;
 import android.graphics.Canvas;
 import android.net.Uri;
 import android.util.Base64;
 import android.view.View;
+import android.widget.ScrollView;
 
 import com.facebook.react.bridge.Promise;
 import com.facebook.react.uimanager.NativeViewHierarchyManager;
     private File output;
     private String result;
     private Promise promise;
+    private Boolean isScrollView;
 
     public ViewShot(
             int tag,
             @Nullable Integer height,
             File output,
             String result,
+            Boolean isScrollView,
             Promise promise) {
         this.tag = tag;
         this.extension = extension;
         this.height = height;
         this.output = output;
         this.result = result;
+        this.isScrollView = isScrollView;
         this.promise = promise;
     }
 
     private void captureView (View view, OutputStream os) {
         int w = view.getWidth();
         int h = view.getHeight();
+
         if (w <= 0 || h <= 0) {
             throw new RuntimeException("Impossible to snapshot the view: view is invalid");
         }
-        Bitmap bitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
+
+        //evaluate real height
+        if (this.isScrollView){
+            h=0;
+            ScrollView scrollView = (ScrollView)view;
+            for (int i = 0; i < scrollView.getChildCount(); i++) {
+                h += scrollView.getChildAt(i).getHeight();
+            }
+        }
+        Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
         Canvas c = new Canvas(bitmap);
         view.draw(c);