Refactor and simplify color processing

lib/extract/extractBrush.js

@@ -1,5 +1,4 @@
-import extractColor from './extractColor';
-import { Platform } from 'react-native';
+import extractColor, { integerColor } from './extractColor';
 
 const urlIdPattern = /^url\(#(.+)\)$/;
 
@@ -8,7 +7,7 @@ const currentColorBrush = [2];
 export default function extractBrush(color) {
   if (typeof color === 'number') {
     if (color >>> 0 === color && color >= 0 && color <= 0xffffffff) {
-      return [0, Platform.OS === 'android' ? color | 0x0 : color];
+      return [0, integerColor(color)];
     }
   }
 

lib/extract/extractColor.js

@@ -345,7 +345,7 @@ function rgbFromString(string) {
       return null;
     }
 
-    return Platform.OS === 'android' ? rgb | 0x0 : rgb;
+    return integerColor(rgb);
   } else {
     return null;
   }
@@ -403,11 +403,22 @@ function colorFromString(string) {
   }
 }
 
+const identity = x => x;
+
+const toSignedInt32 = x => x | 0x0;
+
+// Android use 32 bit *signed* integer to represent the color
+// We utilize the fact that bitwise operations in JS also operates on
+// signed 32 bit integers, so that we can use those to convert from
+// *unsigned* to *signed* 32bit in that way.
+export const integerColor =
+  Platform.OS === 'android' ? toSignedInt32 : identity;
+
 // Returns 0xaarrggbb or null
 export default function extractColor(color) {
   if (typeof color === 'number') {
     if (color >>> 0 === color && color >= 0 && color <= 0xffffffff) {
-      return Platform.OS === 'android' ? color | 0x0 : color;
+      return integerColor(color);
     }
     return null;
   }
@@ -430,9 +441,5 @@ export default function extractColor(color) {
       Math.round(b * 255)) >>>
     0;
 
-  // Android use 32 bit *signed* integer to represent the color
-  // We utilize the fact that bitwise operations in JS also operates on
-  // signed 32 bit integers, so that we can use those to convert from
-  // *unsigned* to *signed* 32bit int that way.
-  return Platform.OS === 'android' ? int32Color | 0x0 : int32Color;
+  return integerColor(int32Color);
 }

lib/extract/extractFill.js

@@ -1,7 +1,6 @@
 import extractBrush from './extractBrush';
 import extractOpacity from './extractOpacity';
-import { colorNames } from './extractColor';
-import { Platform } from 'react-native';
+import { colorNames, integerColor } from './extractColor';
 
 const fillRules = {
   evenodd: 0,
@@ -10,10 +9,7 @@ const fillRules = {
 
 // default fill is black
 const black = colorNames.black;
-const defaultFill = [
-  0,
-  Platform.OS === 'android' ? black | 0x0 : black,
-];
+const defaultFill = [0, integerColor(black)];
 
 export default function extractFill(props, styleProperties) {
   if (props.fill != null) {