Another iPhone - CGBitmapContextCreateImage Leak

Question

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• iPhone - UIImage Leak, ObjectAlloc Building

I\'m having a similar problem. The pointer from the malloc in create_bitmap

Answer 1

I had this problem and it drove me nuts for a few days. After much digging and noticing a leak in CG Raster Data using Instruments.

The problem seems to lie inside CoreGraphics. My problem was when i was using CGBitmapContextCreateImage in a tight loop it would over a period of time retain some images (800kb each) and this slowly leaked out.

After a few days of tracing with Instruments I found a workaround was to use CGDataProviderCreateWithData method instead. The interesting thing was the output was the same CGImageRef but this time there would be no CG Raster Data used in VM by Core graphics and no leak. Im assuming this is an internal problem or were misusing it.

Here is the code that saved me:

@autoreleasepool {
    CGImageRef cgImage;
    CreateCGImageFromCVPixelBuffer(pixelBuffer,&cgImage);

    UIImage *image= [UIImage imageWithCGImage:cgImage scale:1.0 orientation:UIImageOrientationUp];

    // DO SOMETHING HERE WITH IMAGE

    CGImageRelease(cgImage);
}

The key was using CGDataProviderCreateWithData in the method below.

static OSStatus CreateCGImageFromCVPixelBuffer(CVPixelBufferRef pixelBuffer, CGImageRef *imageOut)
    {
        OSStatus err = noErr;
        OSType sourcePixelFormat;
        size_t width, height, sourceRowBytes;
        void *sourceBaseAddr = NULL;
        CGBitmapInfo bitmapInfo;
        CGColorSpaceRef colorspace = NULL;
        CGDataProviderRef provider = NULL;
        CGImageRef image = NULL;

        sourcePixelFormat = CVPixelBufferGetPixelFormatType( pixelBuffer );
        if ( kCVPixelFormatType_32ARGB == sourcePixelFormat )
            bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaNoneSkipFirst;
        else if ( kCVPixelFormatType_32BGRA == sourcePixelFormat )
            bitmapInfo = kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst;
        else
            return -95014; // only uncompressed pixel formats

        sourceRowBytes = CVPixelBufferGetBytesPerRow( pixelBuffer );
        width = CVPixelBufferGetWidth( pixelBuffer );
        height = CVPixelBufferGetHeight( pixelBuffer );

        CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
        sourceBaseAddr = CVPixelBufferGetBaseAddress( pixelBuffer );

        colorspace = CGColorSpaceCreateDeviceRGB();

        CVPixelBufferRetain( pixelBuffer );
        provider = CGDataProviderCreateWithData( (void *)pixelBuffer, sourceBaseAddr, sourceRowBytes * height, ReleaseCVPixelBuffer);
        image = CGImageCreate(width, height, 8, 32, sourceRowBytes, colorspace, bitmapInfo, provider, NULL, true, kCGRenderingIntentDefault);

        if ( err && image ) {
            CGImageRelease( image );
            image = NULL;
        }
        if ( provider ) CGDataProviderRelease( provider );
        if ( colorspace ) CGColorSpaceRelease( colorspace );
        *imageOut = image;
        return err;
    }

    static void ReleaseCVPixelBuffer(void *pixel, const void *data, size_t size)
    {
        CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)pixel;
        CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
        CVPixelBufferRelease( pixelBuffer );
    }