Add an SkImageGeneratorCG

src/ports/SkImageGeneratorCG.cpp

Index: src/ports/SkImageGeneratorCG.cpp
diff --git a/src/ports/SkImageGeneratorCG.cpp b/src/ports/SkImageGeneratorCG.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..cf00ea703dae01a013feaf9b8471734dbc46e83f
--- /dev/null
+++ b/src/ports/SkImageGeneratorCG.cpp
@@ -0,0 +1,123 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkImageGeneratorCG.h"
+#include "SkUnpremultiply.h"
+
+#ifdef SK_BUILD_FOR_MAC
+#include <ApplicationServices/ApplicationServices.h>
+#endif
+
+#ifdef SK_BUILD_FOR_IOS
+#include <CoreGraphics/CoreGraphics.h>
+#include <ImageIO/ImageIO.h>
+#include <MobileCoreServices/MobileCoreServices.h>
+#endif
+
+static CGImageSourceRef data_to_CGImageSrc(SkData* data) {
+    CGDataProviderRef cgData = CGDataProviderCreateWithData(data, data->data(), data->size(),
+            nullptr);
+    if (!cgData) {
+        return nullptr;
+    }
+    CGImageSourceRef imageSrc = CGImageSourceCreateWithDataProvider(cgData, 0);
+    CGDataProviderRelease(cgData);
+    return imageSrc;
+}
+
+SkImageGenerator* SkImageGeneratorCG::NewFromEncodedCG(SkData* data) {
+    CGImageSourceRef imageSrc = data_to_CGImageSrc(data);
+    if (!imageSrc) {
+        return nullptr;
+    }
+    
+    // Make sure we call CFRelease to free the imageSrc.  Since CFRelease actually takes
+    // a const void*, we must cast the imageSrc to a const void*.
+    SkAutoTCallVProc<const void, CFRelease> autoImageSrc(imageSrc);
+
+    CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(imageSrc, 0, nullptr);
+    if (!properties) {
+        return nullptr;
+    }
+    
+    CFNumberRef widthRef = (CFNumberRef) (CFDictionaryGetValue(properties,
+            kCGImagePropertyPixelWidth));
+    CFNumberRef heightRef = (CFNumberRef) (CFDictionaryGetValue(properties,
+            kCGImagePropertyPixelHeight));
+    if (nullptr == widthRef || nullptr == heightRef) {
+        return nullptr;
+    }
+    bool hasAlpha = (bool) (CFDictionaryGetValue(properties,
+            kCGImagePropertyHasAlpha));
+
+    int width, height;
+    if (!CFNumberGetValue(widthRef, kCFNumberIntType, &width) ||
+            !CFNumberGetValue(heightRef, kCFNumberIntType, &height)) {
+        return nullptr;
+    }
+    
+    SkAlphaType alphaType = hasAlpha ? kPremul_SkAlphaType : kOpaque_SkAlphaType;
+    SkImageInfo info = SkImageInfo::Make(width, height, kN32_SkColorType, alphaType);
+
+    // FIXME: We have the opportunity to extract color space information here,
+    //        though I think it makes sense to wait until we understand how
+    //        we want to communicate it to the generator.
+
+    return new SkImageGeneratorCG(info, autoImageSrc.detach(), data);
+}
+
+SkImageGeneratorCG::SkImageGeneratorCG(const SkImageInfo& info, const void* imageSrc, SkData* data)
+    : INHERITED(info)
+    , fImageSrc(imageSrc)
+    , fData(SkRef(data))
+{}
+
+SkData* SkImageGeneratorCG::onRefEncodedData(SK_REFENCODEDDATA_CTXPARAM) {
+    return SkRef(fData.get());
+}
+
+bool SkImageGeneratorCG::onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+        SkPMColor ctable[], int* ctableCount) {
+    if (kN32_SkColorType != info.colorType()) {
+        // FIXME: Support other colorTypes.
+        return false;
+    }
+    
+    switch (info.alphaType()) {
+        case kOpaque_SkAlphaType:
+            if (kOpaque_SkAlphaType != this->getInfo().alphaType()) {
+                return false;
+            }
+            break;
+        case kPremul_SkAlphaType:
+            break;
+        default:
+            return false;
+    }
+    
+    CGImageRef image = CGImageSourceCreateImageAtIndex((CGImageSourceRef) fImageSrc.get(), 0,
+            nullptr);
+    if (!image) {
+        return false;
+    }
+    SkAutoTCallVProc<CGImage, CGImageRelease> autoImage(image);
+
+    // FIXME: Using this function (as opposed to swizzling ourselves) greatly
+    //        restricts the color and alpha types that we support.  If we
+    //        swizzle ourselves, we can add support for:
+    //            kUnpremul_SkAlphaType
+    //            16-bit per component RGBA
+    //            kGray_8_SkColorType
+    //            kIndex_8_SkColorType
+    //        Additionally, it would be interesting to compare the performance
+    //        of SkSwizzler with CG's built in swizzler.
+    if (!SkCopyPixelsFromCGImage(info, rowBytes, pixels, image)) {
+        return false;
+    }
+
+    return true;
+}