expose CGImage -> SkBitmap

src/utils/mac/SkCreateCGImageRef.cpp

Index: src/utils/mac/SkCreateCGImageRef.cpp
diff --git a/src/utils/mac/SkCreateCGImageRef.cpp b/src/utils/mac/SkCreateCGImageRef.cpp
index 00166e9ed7488b4976d8c426a90061a7d3b40fd3..f6826da8d3162e11a83b6da9d54ab560f7d2492d 100644
--- a/src/utils/mac/SkCreateCGImageRef.cpp
+++ b/src/utils/mac/SkCreateCGImageRef.cpp
@@ -231,3 +231,71 @@ bool SkPDFDocumentToBitmap(SkStream* stream, SkBitmap* output) {
     output->swap(bitmap);
     return true;
 }
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+SK_API bool SkCopyPixelsFromCGImage(const SkImageInfo& info, size_t rowBytes, void* pixels,
+                                    CGImageRef image) {
+    uint32_t cg_bitmap_info = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast;
+    // TODO: update cg_bitmap_info based on colortype
+    switch (info.colorType()) {
+        case kRGB_565_SkColorType:
+            break;
+        case kRGBA_8888_SkColorType:
+            break;
+        case kBGRA_8888_SkColorType:
+            break;
+        default:
+            return false;   // no other colortypes are supported (afaik)
+    }
+
+    CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
+    CGContextRef cg = CGBitmapContextCreate(pixels, info.width(), info.height(), 8, rowBytes, cs,

[scroggo, 2014/04/21 20:18:44]

Isn't this 8 specific to 8888? If info.colorType() was 565, would this be the
correct value?

[reed1, 2014/04/21 20:44:41]

Yes. that is specfic, and so is the cg_bitmap_info at the moment. I won't land
this until those are fixed.

+                                            cg_bitmap_info);
+    CFRelease(cs);
+    if (NULL == cg) {
+        return false;
+    }
+
+    // use this blend mode, to avoid having to erase the pixels first, and to avoid CG performing
+    // any blending (which could introduce errors and be slower).
+    CGContextSetBlendMode(cg, kCGBlendModeCopy);
+
+    CGContextDrawImage(cg, CGRectMake(0, 0, info.width(), info.height()), image);
+    CGContextRelease(cg);
+    return true;
+}
+
+bool SkCreateBitmapFromCGImage(SkBitmap* dst, CGImageRef image, SkISize* scaleToFit) {
+    const int width = scaleToFit ? scaleToFit->width() : SkToInt(CGImageGetWidth(image));
+    const int height = scaleToFit ? scaleToFit->height() : SkToInt(CGImageGetHeight(image));
+    SkImageInfo info = SkImageInfo::MakeN32Premul(width, height);
+
+    SkBitmap tmp;
+    if (!tmp.allocPixels(info)) {
+        return false;
+    }
+
+    if (!SkCopyPixelsFromCGImage(tmp.info(), tmp.rowBytes(), tmp.getPixels(), image)) {
+        return false;
+    }
+
+    CGImageAlphaInfo cgInfo = CGImageGetAlphaInfo(image);

[scroggo, 2014/04/21 20:18:44]

I'm not a big fan of this duplicated code, if we can avoid it.

[reed1, 2014/04/21 20:44:41]

Working on it, but haven't seen how to share yet. Perhaps in a separate CL

+    switch (cgInfo) {
+        case kCGImageAlphaNone:
+        case kCGImageAlphaNoneSkipLast:
+        case kCGImageAlphaNoneSkipFirst:
+            SkASSERT(SkBitmap::ComputeIsOpaque(tmp));
+            tmp.setAlphaType(kOpaque_SkAlphaType);
+            break;
+        default:
+            // we don't know if we're opaque or not, so compute it.
+            if (SkBitmap::ComputeIsOpaque(tmp)) {
+                tmp.setAlphaType(kOpaque_SkAlphaType);
+            }
+    }
+
+    *dst = tmp;
+    return true;
+}
+