CoreGraphics: Fix bug where subsection images were rendered incorrectly

modules/juce_graphics/contexts/juce_GraphicsContext.cpp

@@ -871,4 +871,68 @@ Graphics::ScopedSaveState::~ScopedSaveState()
     context.restoreState();
 }
 
+//==============================================================================
+//==============================================================================
+#if JUCE_UNIT_TESTS
+
+class GraphicsTests : public UnitTest
+{
+public:
+    GraphicsTests() : UnitTest ("Graphics", UnitTestCategories::graphics) {}
+
+    void runTest() override
+    {
+        beginTest ("Render image subsection");
+        {
+            renderImageSubsection (NativeImageType{}, NativeImageType{});
+        }
+    }
+
+private:
+    void renderImageSubsection (const ImageType& sourceType, const ImageType& targetType)
+    {
+        const auto sourceColour = Colours::cyan;
+        const auto sourceOffset = 49;
+
+        const Image source { Image::ARGB, 50, 50, true, sourceType };
+        const Image target { Image::ARGB, 50, 50, true, targetType };
+
+        const auto subsection = source.getClippedImage (Rectangle { sourceOffset, sourceOffset, 1, 1 });
+
+        Image::BitmapData { subsection, Image::BitmapData::writeOnly }.setPixelColour (0, 0, sourceColour);
+
+        {
+            // Render the subsection image so that it fills 'target'
+            Graphics g { target };
+            g.drawImage (subsection,
+                         0, 0, target.getWidth(), target.getHeight(),
+                         0, 0, 1, 1);
+        }
+
+        {
+            // Check that all pixels in 'target' match the bottom right pixel of 'source'
+            const Image::BitmapData bitmap { target, Image::BitmapData::readOnly };
+
+            int numFailures = 0;
+
+            for (auto y = 0; y < bitmap.height; ++y)
+            {
+                for (auto x = 0; x < bitmap.width; ++x)
+                {
+                    const auto targetColour = bitmap.getPixelColour (x, y);
+
+                    if (targetColour != sourceColour)
+                        ++numFailures;
+                }
+            }
+
+            expect (numFailures == 0);
+        }
+    }
+};
+
+static GraphicsTests graphicsTests;
+
+#endif
+
 } // namespace juce

modules/juce_graphics/images/juce_Image.cpp

@@ -282,7 +282,7 @@ public:
 
    #if JUCE_MAC || JUCE_IOS
     CGContextRef getCGContext() const { return impl->getCGContext(); }
-    CGImageRef getCGImage (CGColorSpaceRef x) const { return impl->getCGImage (x); }
+    CFUniquePtr<CGImageRef> getCGImage (CGColorSpaceRef x) const { return impl->getCGImage (x); }
    #endif
 
 private:
@@ -297,7 +297,7 @@ private:
 
        #if JUCE_MAC || JUCE_IOS
         virtual CGContextRef getCGContext() const = 0;
-        virtual CGImageRef getCGImage (CGColorSpaceRef x) const = 0;
+        virtual CFUniquePtr<CGImageRef> getCGImage (CGColorSpaceRef x) const = 0;
        #endif
     };
 
@@ -316,7 +316,7 @@ private:
 
        #if JUCE_MAC || JUCE_IOS
         CGContextRef getCGContext() const override { return impl.getCGContext(); }
-        CGImageRef getCGImage (CGColorSpaceRef x) const override { return impl.getCGImage (x); }
+        CFUniquePtr<CGImageRef> getCGImage (CGColorSpaceRef x) const override { return impl.getCGImage (x); }
        #endif
 
     private:
@@ -417,9 +417,12 @@ public:
                 return self->sourceImage->getNativeExtensions().getCGContext();
             }
 
-            CGImageRef getCGImage (CGColorSpaceRef colourSpace) const
+            CFUniquePtr<CGImageRef> getCGImage (CGColorSpaceRef colourSpace) const
             {
-                return self->sourceImage->getNativeExtensions().getCGImage (colourSpace);
+                const auto& parentNative = self->sourceImage->getNativeExtensions();
+                const auto parentImage = parentNative.getCGImage (colourSpace);
+                return CFUniquePtr<CGImageRef> { CGImageCreateWithImageInRect (parentImage.get(),
+                                                                               makeCGRect (self->area + parentNative.getTopLeft())) };
             }
            #endif
 
@@ -518,7 +521,7 @@ auto ImagePixelData::getNativeExtensions() -> NativeExtensions
 
        #if JUCE_MAC || JUCE_IOS
         CGContextRef getCGContext() const { return {}; }
-        CGImageRef getCGImage (CGColorSpaceRef) const { return {}; }
+        CFUniquePtr<CGImageRef> getCGImage (CGColorSpaceRef) const { return {}; }
        #endif
     };
 

modules/juce_graphics/native/juce_CoreGraphicsContext_mac.mm

@@ -144,9 +144,9 @@ public:
     }
 
     //==============================================================================
-    static CGImageRef getCachedImageRef (const Image& juceImage, CGColorSpaceRef colourSpace)
+    static CFUniquePtr<CGImageRef> getCachedImageRef (const Image& juceImage, CGColorSpaceRef colourSpace)
     {
-        auto* cgim = std::invoke ([&]() -> CGImageRef
+        auto cgim = std::invoke ([&]() -> CFUniquePtr<CGImageRef>
         {
             if (auto ptr = juceImage.getPixelData())
                 return ptr->getNativeExtensions().getCGImage (colourSpace);
@@ -155,7 +155,7 @@ public:
         });
 
         if (cgim != nullptr)
-            return CGImageRetain (cgim);
+            return cgim;
 
         const Image::BitmapData srcData (juceImage, Image::BitmapData::readOnly);
 
@@ -163,13 +163,17 @@ public:
         CFUniquePtr<CFDataRef> data (CFDataCreate (nullptr, (const UInt8*) srcData.data, (CFIndex) usableSize));
         detail::DataProviderPtr provider { CGDataProviderCreateWithCFData (data.get()) };
 
-        return CGImageCreate ((size_t) srcData.width,
+        return CFUniquePtr<CGImageRef> { CGImageCreate ((size_t) srcData.width,
-                              (size_t) srcData.height,
+                                                        (size_t) srcData.height,
-                              8,
+                                                        8,
-                              (size_t) srcData.pixelStride * 8,
+                                                        (size_t) srcData.pixelStride * 8,
-                              (size_t) srcData.lineStride,
+                                                        (size_t) srcData.lineStride,
-                              colourSpace, getCGImageFlags (juceImage.getFormat()), provider.get(),
+                                                        colourSpace,
-                              nullptr, true, kCGRenderingIntentDefault);
+                                                        getCGImageFlags (juceImage.getFormat()),
+                                                        provider.get(),
+                                                        nullptr,
+                                                        true,
+                                                        kCGRenderingIntentDefault) };
     }
 
     //==============================================================================
@@ -185,10 +189,10 @@ public:
         HeapBlock<uint8> data;
     };
 
-    CGImageRef getCGImage (CGColorSpaceRef colourSpace)
+    CFUniquePtr<CGImageRef> getCGImage (CGColorSpaceRef colourSpace)
     {
         if (cachedImageRef != nullptr)
-            return cachedImageRef.get();
+            return CFUniquePtr<CGImageRef> { CGImageRetain (cachedImageRef.get()) };
 
         const Image::BitmapData srcData { Image { this }, Image::BitmapData::readOnly };
 
@@ -205,7 +209,7 @@ public:
                                              colourSpace, getCGImageFlags (pixelFormat), provider.get(),
                                              nullptr, true, kCGRenderingIntentDefault));
 
-        return cachedImageRef.get();
+        return CFUniquePtr<CGImageRef> { CGImageRetain (cachedImageRef.get()) };
     }
 
     ImageDataContainer::Ptr imageData = new ImageDataContainer();
@@ -222,7 +226,7 @@ public:
                 return self->context.get();
             }
 
-            CGImageRef getCGImage (CGColorSpaceRef x) const
+            CFUniquePtr<CGImageRef> getCGImage (CGColorSpaceRef x) const
             {
                 return self->getCGImage (x);
             }
@@ -1200,7 +1204,7 @@ Image juce_createImageFromCIImage (CIImage* im, int w, int h)
 
 CGImageRef juce_createCoreGraphicsImage (const Image& juceImage, CGColorSpaceRef colourSpace)
 {
-    return CoreGraphicsPixelData::getCachedImageRef (juceImage, colourSpace);
+    return CoreGraphicsPixelData::getCachedImageRef (juceImage, colourSpace).release();
 }
 
 CGContextRef juce_getImageContext (const Image& image)