[ASDisplayNode] Use kCGBlendModeCopy in a Couple More Places (#2250)

* Use blend mode copy in a couple more places

* Add some tests

AsyncDisplayKit/ASImageNode.mm

@@ -677,7 +677,7 @@ extern asimagenode_modification_block_t ASImageNodeRoundBorderModificationBlock(
     [roundOutline addClip];
 
     // Draw the original image
-    [originalImage drawAtPoint:CGPointZero];
+    [originalImage drawAtPoint:CGPointZero blendMode:kCGBlendModeCopy alpha:1];
 
     // Draw a border on top.
     if (borderWidth > 0.0) {
@@ -700,7 +700,7 @@ extern asimagenode_modification_block_t ASImageNodeTintColorModificationBlock(UI
     // Set color and render template
     [color setFill];
     UIImage *templateImage = [originalImage imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
-    [templateImage drawAtPoint:CGPointZero];
+    [templateImage drawAtPoint:CGPointZero blendMode:kCGBlendModeCopy alpha:1];
     
     UIImage *modifiedImage = UIGraphicsGetImageFromCurrentImageContext();
     UIGraphicsEndImageContext();

AsyncDisplayKit/Private/ASDisplayNode+AsyncDisplay.mm

@@ -14,6 +14,7 @@
 #import "ASAssert.h"
 #import "ASDisplayNodeInternal.h"
 #import "ASDisplayNode+FrameworkPrivate.h"
+#import "ASInternalHelpers.h"
 
 @interface ASDisplayNode () <_ASDisplayLayerDelegate>
 @end
@@ -113,7 +114,9 @@
       if (displayBlock) {
         UIImage *image = (UIImage *)displayBlock();
         if (image) {
-          [image drawInRect:bounds];
+          BOOL opaque = ASImageAlphaInfoIsOpaque(CGImageGetAlphaInfo(image.CGImage));
+          CGBlendMode blendMode = opaque ? kCGBlendModeCopy : kCGBlendModeNormal;
+          [image drawInRect:bounds blendMode:blendMode alpha:1];
         }
       }
     };

AsyncDisplayKitTests/ASImageNodeSnapshotTests.m

@@ -58,4 +58,30 @@
             @"Contents should be 100 x 100 by contents scale.");
 }
 
+- (void)testTintColorBlock
+{
+  UIImage *test = [self testImage];
+  UIImage *tinted = ASImageNodeTintColorModificationBlock([UIColor redColor])(test);
+  ASImageNode *node = [[ASImageNode alloc] init];
+  node.image = tinted;
+  [node layoutThatFits:ASSizeRangeMake(test.size)];
+  
+  ASSnapshotVerifyNode(node, nil);
+}
+
+- (void)testRoundedCornerBlock
+{
+  UIGraphicsBeginImageContext(CGSizeMake(100, 100));
+  [[UIColor blueColor] setFill];
+  UIRectFill(CGRectMake(0, 0, 100, 100));
+  UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
+  UIGraphicsEndImageContext();
+  UIImage *rounded = ASImageNodeRoundBorderModificationBlock(2, [UIColor redColor])(result);
+  ASImageNode *node = [[ASImageNode alloc] init];
+  node.image = rounded;
+  [node layoutThatFits:ASSizeRangeMake(rounded.size)];
+  
+  ASSnapshotVerifyNode(node, nil);
+}
+
 @end