add disableOverlay prop

Author: Joshua Jahans

README.md

@@ -61,7 +61,8 @@ The `HeaderImageScrollView` handle also the following props. None is required :
 | `maxOverlayOpacity` | `number` | `0.3` | Opacity of a black overlay on the header when in navbar mode | [example](https://github.com/bamlab/react-native-image-header-scroll-view-example/blob/3b9d2d0d7f71c6bf877e2d10cc65c9ab7e1b484d/src/Pages/TvShow.js#L96) |
 | `overlayColor` | `string` | `black` | Color of the overlay on the header | [example](https://github.com/bamlab/react-native-image-header-scroll-view-example/blob/master/src/Pages/Colors.js#L16) |
 |`headerContainerStyle`|`Object`|`undefined`|Optional styles to be passed to the container of the header component|
-|`disableHeaderGrow`|`boolean`|`undefined`|Disable to grow effect on the header
+|`disableHeaderGrow`|`boolean`|`undefined`|Disable to grow effect on the header|
+|`disableOverlay`|`boolean`|`undefined`|Disable the image overlay|
 
 ### Foreground
 

src/ImageHeaderScrollView.js

@@ -44,6 +44,7 @@ export type Props = ScrollViewProps & {
   headerImage?: ?SourceProps,
   headerContainerStyle?: ?Object,
   disableHeaderGrow?: ?boolean,
+  disableOverlay?: ?boolean,
 };
 
 export type DefaultProps = {
@@ -154,7 +155,7 @@ class ImageHeaderScrollView extends Component<Props, State> {
     return (
       <Animated.View style={[styles.header, headerTransformStyle, this.props.headerContainerStyle]}>
         {this.renderHeaderProps()}
-        <Animated.View style={overlayStyle} />
+        {!this.props.disableOverlay && <Animated.View style={overlayStyle} />}
         <View style={styles.fixedForeground}>{this.props.renderFixedForeground()}</View>
       </Animated.View>
     );