Decode image data directly on iOS

...instead of rendering to a core graphics context and then copying the context's buffer.

Seems like our alpha un-premultiply logic is no longer taking affect: https://github.com/rive-app/rive/blob/1c9233455851e5d346c4c97b01fdf74a5966017d/packages/runtime_ios/Source/Renderer/RenderContextManager.mm#L74-L82

Expected:
<img src="https://rive-public-testing.s3.us-west-1.amazonaws.com/golden-tests/ios/2024-07-31/127/golden/mesh.png"/>
Currently:
<img src="https://rive-public-testing.s3.us-west-1.amazonaws.com/golden-tests/ios/2024-07-31/127/iphone-15-pro-max/mesh.png"/>

Thread with details here: https://2dimensions.slack.com/archives/C06ER4J62BA/p1722438338690329

This fixes the issue by extracting the decoded PNG bytes directly (which are un-premultiplied).

Diffs=
714b8894f Decode image data directly on iOS (#7820)

Co-authored-by: Chris Dalton <[email protected]>
Co-authored-by: Luigi Rosso <[email protected]>

.rive_head

@@ -1 +1 @@
-55de8286c5ba680de950a3a0aac26e13bb890d6b
+714b8894f37ab931a1df4b27d63c1e0991a97e3a

Source/Renderer/PlatformCGImage.mm

@@ -49,40 +49,17 @@ bool PlatformCGImageDecode(const uint8_t* encodedBytes,
             break;
     }
 
-    // Now create a drawing context to produce RGBA pixels
-
-    const size_t bitsPerComponent = 8;
-    CGBitmapInfo cgInfo = kCGBitmapByteOrder32Big; // rgba
-    if (isOpaque)
-    {
-        cgInfo |= kCGImageAlphaNoneSkipLast;
-    }
-    else
-    {
-        cgInfo |= kCGImageAlphaPremultipliedLast; // premul
-    }
+    CFDataRef dataRef = CGDataProviderCopyData(CGImageGetDataProvider(image));
+    const UInt8* pixelData = CFDataGetBytePtr(dataRef);
     const size_t width = CGImageGetWidth(image);
     const size_t height = CGImageGetHeight(image);
     const size_t rowBytes = width * 4; // 4 bytes per pixel
     const size_t size = rowBytes * height;
 
-    std::vector<uint8_t> pixels;
-    pixels.resize(size);
-
-    AutoCF cs = CGColorSpaceCreateDeviceRGB();
-    AutoCF cg =
-        CGBitmapContextCreate(pixels.data(), width, height, bitsPerComponent, rowBytes, cs, cgInfo);
-    if (!cg)
-    {
-        return false;
-    }
-
-    CGContextSetBlendMode(cg, kCGBlendModeCopy);
-    CGContextDrawImage(cg, CGRectMake(0, 0, width, height), image);
-
     platformImage->width = rive::castTo<uint32_t>(width);
     platformImage->height = rive::castTo<uint32_t>(height);
     platformImage->opaque = isOpaque;
-    platformImage->pixels = std::move(pixels);
+    platformImage->pixels = std::vector<uint8_t>(pixelData, pixelData + size);
+    CFRelease(dataRef);
     return true;
 }