Add support for CGImageCreateWithMask. (#1555)

Fixes #1425.

Frameworks/CoreGraphics/CGImage.mm

@@ -525,13 +525,34 @@ CGImageRef CGImageCreateCopyWithColorSpace(CGImageRef ref, CGColorSpaceRef color
 }
 
 /**
- @Status Stub
+ @Status Interoperable
+ @Notes This function does not defer the composition of its mask.
+        This function supports non-grayscale alpha masks, unlike the reference platform.
  */
 CGImageRef CGImageCreateWithMask(CGImageRef image, CGImageRef mask) {
-    // TODO  #1425 - masks are applied during rendering via D2D.
     RETURN_NULL_IF(!image);
-    UNIMPLEMENTED();
-    return StubReturn();
+    RETURN_NULL_IF(!mask);
+    RETURN_NULL_IF(CGImageIsMask(image));
+
+    size_t width = CGImageGetWidth(image);
+    size_t height = CGImageGetHeight(image);
+
+    woc::unique_cf<CGContextRef> context{ CGBitmapContextCreate(nullptr,
+                                                                width,
+                                                                height,
+                                                                8,
+                                                                width * 4,
+                                                                CGImageGetColorSpace(image),
+                                                                kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Big) };
+    RETURN_NULL_IF(!context);
+
+    CGRect rect{
+        CGPointZero, { width, height },
+    };
+    CGContextClipToMask(context.get(), rect, mask);
+    CGContextDrawImage(context.get(), rect, image);
+
+    return CGBitmapContextCreateImage(context.get());
 }
 
 /**

include/CoreGraphics/CGImage.h

@@ -82,7 +82,7 @@ COREGRAPHICS_EXPORT CGImageRef CGImageCreateWithPNGDataProvider(CGDataProviderRe
 
 COREGRAPHICS_EXPORT CGImageRef CGImageCreateWithImageInRect(CGImageRef image, CGRect rect);
 
-COREGRAPHICS_EXPORT CGImageRef CGImageCreateWithMask(CGImageRef image, CGImageRef mask) STUB_METHOD;
+COREGRAPHICS_EXPORT CGImageRef CGImageCreateWithMask(CGImageRef image, CGImageRef mask);
 
 COREGRAPHICS_EXPORT CGImageRef CGImageCreateWithMaskingColors(CGImageRef image, const CGFloat* components) STUB_METHOD;
 

tests/unittests/CoreGraphics.drawing/CGContextDrawing_ImageMaskTests.cpp

@@ -366,3 +366,74 @@ DRAW_TEST(CGContextClipping, ClipATransparencyLayer) {
     // If the clip mask applies twice (wrong) it will be 25%.
     CGContextEndTransparencyLayer(context);
 }
+
+DRAW_TEST(CGImage, CreateWithSameSizeMask) {
+    auto drawingConfig = DrawingTestConfig::Get();
+
+    woc::unique_cf<CFStringRef> testFilename{ _CFStringCreateWithStdString(drawingConfig->GetResourcePath("jpg1.jpg")) };
+    woc::unique_cf<CGImageRef> image{ _CGImageCreateFromJPEGFile(testFilename.get()) };
+    ASSERT_NE(nullptr, image);
+
+    CGSize imageSize{ static_cast<CGFloat>(CGImageGetWidth(image.get())), static_cast<CGFloat>(CGImageGetHeight(image.get())) };
+
+    woc::unique_cf<CGImageRef> alphaMask{
+        __CreateClipImage(imageSize,
+            ClippingTypeMask,
+            [](CGContextRef context, CGSize size, ClippingType clipType) {
+                CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);
+                CGContextFillRect(context, { CGPointZero, size });
+
+                CGContextSetRGBStrokeColor(context, 0.0, 0.0, 0.0, 1.0);
+                CGContextSetLineWidth(context, 10.0);
+                CGContextStrokeRect(context, CGRectInset({ CGPointZero, size }, 20, 20));
+            })
+    };
+
+    ASSERT_NE(nullptr, alphaMask);
+
+    woc::unique_cf<CGImageRef> preMaskedImage{ CGImageCreateWithMask(image.get(), alphaMask.get()) };
+
+    ASSERT_NE(nullptr, preMaskedImage);
+
+    CGContextRef context = GetDrawingContext();
+    CGRect bounds = GetDrawingBounds();
+
+    CGContextDrawImage(context, bounds, preMaskedImage.get());
+}
+
+DRAW_TEST(CGImage, CreateWithScaledMask) {
+    auto drawingConfig = DrawingTestConfig::Get();
+
+    woc::unique_cf<CFStringRef> testFilename{ _CFStringCreateWithStdString(drawingConfig->GetResourcePath("jpg1.jpg")) };
+    woc::unique_cf<CGImageRef> image{ _CGImageCreateFromJPEGFile(testFilename.get()) };
+    ASSERT_NE(nullptr, image);
+
+    CGSize imageSize{ static_cast<CGFloat>(CGImageGetWidth(image.get())), static_cast<CGFloat>(CGImageGetHeight(image.get())) };
+
+    woc::unique_cf<CGImageRef> alphaMask{
+        __CreateClipImage({ 64, 64 },
+            ClippingTypeMask,
+            [](CGContextRef context, CGSize size, ClippingType clipType) {
+                CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);
+                CGContextFillRect(context, { CGPointZero, size });
+
+                CGContextSetRGBStrokeColor(context, 0.0, 0.0, 0.0, 1.0);
+                CGContextSetLineWidth(context, 4.0);
+                CGPoint points[]{
+                    { 0, 0 }, { 64, 64 }, { 0, 64 }, { 64, 0 },
+                };
+                CGContextStrokeLineSegments(context, points, 4);
+            })
+    };
+
+    ASSERT_NE(nullptr, alphaMask);
+
+    woc::unique_cf<CGImageRef> preMaskedImage{ CGImageCreateWithMask(image.get(), alphaMask.get()) };
+
+    ASSERT_NE(nullptr, preMaskedImage);
+
+    CGContextRef context = GetDrawingContext();
+    CGRect bounds = GetDrawingBounds();
+
+    CGContextDrawImage(context, bounds, preMaskedImage.get());
+}