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..89cae2beefda37155673a0ffeeb8cca73d898ad9 100644
--- a/src/utils/mac/SkCreateCGImageRef.cpp
+++ b/src/utils/mac/SkCreateCGImageRef.cpp
@@ -9,6 +9,40 @@
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
 
+static uint32_t ComputeCGAlphaInfo_RGBA(SkAlphaType at) {

[scroggo, 2014/04/22 14:58:17]

Should these return CGBitmapInfo for documentation purposes?

[reed1, 2014/04/22 17:51:39]

Done.

+    uint32_t info = kCGBitmapByteOrder32Big;
+    switch (at) {
+        case kOpaque_SkAlphaType:
+        case kIgnore_SkAlphaType:
+            info |= kCGImageAlphaNoneSkipLast;
+            break;
+        case kPremul_SkAlphaType:
+            info |= kCGImageAlphaPremultipliedLast;
+            break;
+        case kUnpremul_SkAlphaType:
+            info |= kCGImageAlphaLast;
+            break;
+    }
+    return info;
+}
+
+static uint32_t ComputeCGAlphaInfo_BGRA(SkAlphaType at) {
+    uint32_t info = kCGBitmapByteOrder32Little;
+    switch (at) {
+        case kOpaque_SkAlphaType:
+        case kIgnore_SkAlphaType:
+            info |= kCGImageAlphaNoneSkipFirst;
+            break;
+        case kPremul_SkAlphaType:
+            info |= kCGImageAlphaPremultipliedFirst;
+            break;
+        case kUnpremul_SkAlphaType:
+            info |= kCGImageAlphaFirst;
+            break;
+    }
+    return info;
+}
+
 static void SkBitmap_ReleaseInfo(void* info, const void* pixelData, size_t size) {
     SkBitmap* bitmap = reinterpret_cast<SkBitmap*>(info);
     delete bitmap;
@@ -22,54 +56,35 @@ static bool getBitmapInfo(const SkBitmap& bm,
         *upscaleTo32 = false;
     }
 
+    const bool opaque = kOpaque_SkAlphaType == bm.alphaType();

[scroggo, 2014/04/22 14:58:17]

It seems like this could go in the 4444 case (the only place it's used).

[reed1, 2014/04/22 17:51:39]

Done.

+    const bool premul = kUnpremul_SkAlphaType != bm.alphaType();

[scroggo, 2014/04/22 14:58:17]

This variable is unused.

[reed1, 2014/04/22 17:51:39]

Done.

+
     switch (bm.colorType()) {
         case kRGB_565_SkColorType:
 #if 0
             // doesn't see quite right. Are they thinking 1555?
             *bitsPerComponent = 5;
             *info = kCGBitmapByteOrder16Little | kCGImageAlphaNone;
-            break;
-#endif
+#else
             if (upscaleTo32) {
                 *upscaleTo32 = true;
             }
-            // fall through
-        case kN32_SkColorType:
-            *bitsPerComponent = 8;
-#if SK_PMCOLOR_BYTE_ORDER(R,G,B,A)
-            *info = kCGBitmapByteOrder32Big;
-            if (bm.isOpaque()) {
-                *info |= kCGImageAlphaNoneSkipLast;
-            } else {
-                *info |= kCGImageAlphaPremultipliedLast;
-            }
-#elif SK_PMCOLOR_BYTE_ORDER(B,G,R,A)
-            // Matches the CGBitmapInfo that Apple recommends for best
-            // performance, used by google chrome.
-            *info = kCGBitmapByteOrder32Little;
-            if (bm.isOpaque()) {
-                *info |= kCGImageAlphaNoneSkipFirst;
-            } else {
-                *info |= kCGImageAlphaPremultipliedFirst;
-            }
-#else
-            // ...add more formats as required...
-#warning Cannot convert SkBitmap to CGImageRef with these shiftmasks. \
-This will probably not work.
-            // Legacy behavior. Perhaps turn this into an error at some
-            // point.
-            *info = kCGBitmapByteOrder32Big;
-            if (bm.isOpaque()) {
-                *info |= kCGImageAlphaNoneSkipLast;
-            } else {
-                *info |= kCGImageAlphaPremultipliedLast;
-            }
+            // now treat like RGBA
+            *info = ComputeCGAlphaInfo_RGBA(kOpaque_SkAlphaType);
 #endif
             break;
+        case kRGBA_8888_SkColorType:
+            *bitsPerComponent = 8;
+            *info = ComputeCGAlphaInfo_RGBA(bm.alphaType());
+            break;
+        case kBGRA_8888_SkColorType:
+            *bitsPerComponent = 8;
+            *info = ComputeCGAlphaInfo_BGRA(bm.alphaType());
+            break;
         case kARGB_4444_SkColorType:
             *bitsPerComponent = 4;
             *info = kCGBitmapByteOrder16Little;
-            if (bm.isOpaque()) {
+            if (opaque) {
                 *info |= kCGImageAlphaNoneSkipLast;
             } else {
                 *info |= kCGImageAlphaPremultipliedLast;
@@ -231,3 +246,73 @@ 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) {
+    CGBitmapInfo cg_bitmap_info = 0;
+    size_t bitsPerComponent = 0;
+    switch (info.colorType()) {
+        case kRGBA_8888_SkColorType:
+            bitsPerComponent = 8;
+            cg_bitmap_info = ComputeCGAlphaInfo_RGBA(info.alphaType());
+            break;
+        case kBGRA_8888_SkColorType:
+            bitsPerComponent = 8;
+            cg_bitmap_info = ComputeCGAlphaInfo_BGRA(info.alphaType());
+            break;
+        default:
+            return false;   // no other colortypes are supported (for now)
+    }
+
+    CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
+    CGContextRef cg = CGBitmapContextCreate(pixels, info.width(), info.height(), bitsPerComponent,
+                                            rowBytes, cs, 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);
+    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;
+}
+