IOSurface - IOS Private API - Capture screenshot in background

Question

I want to capture a screenshot from a background service. Private API is just fine as I don't need to submit to app store. I have already tried UIGetScreenImage and it does not work from background app.

I am using following code which I got from SO. IOSurfaceCreate returns null to me. Any help appreciated.

CFMutableDictionaryRef dict;
        IOSurfaceRef screenSurface = NULL;

        char pixelFormat[4] = {'A','R','G','B'};
        dict = CFDictionaryCreateMutable(kCFAllocatorDefault, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);

        uint32_t width ;
        uint32_t height;
        void *pitch;
        void *bPE;
        void *size;
        CFDictionarySetValue(dict, kIOSurfaceIsGlobal, kCFBooleanTrue);
        CFDictionarySetValue(dict, kIOSurfaceBytesPerRow, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &pitch));
        CFDictionarySetValue(dict, kIOSurfaceBytesPerElement, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &bPE));
        CFDictionarySetValue(dict, kIOSurfaceWidth, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &width));
        CFDictionarySetValue(dict, kIOSurfaceHeight, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &height));
        CFDictionarySetValue(dict, kIOSurfacePixelFormat, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, pixelFormat));
        CFDictionarySetValue(dict, kIOSurfaceAllocSize, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &size));

        IOSurfaceRef destSurf = IOSurfaceCreate(dict);
        IOSurfaceAcceleratorRef outAcc;
        IOSurfaceAcceleratorCreate(NULL, 0, &outAcc);

        CFDictionaryRef ed = (__bridge CFDictionaryRef)[NSDictionary dictionaryWithObjectsAndKeys: nil];
        IOSurfaceAcceleratorTransferSurface(outAcc, screenSurface, destSurf, ed, NULL);
        uint32_t aseed;
        IOSurfaceUnlock(screenSurface, kIOSurfaceLockReadOnly, &aseed);

        CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, IOSurfaceGetBaseAddress(destSurf), (width*height*4), NULL);
        CGImageRef cgImage=CGImageCreate(width, height, 8, 8*4, IOSurfaceGetBytesPerRow(destSurf), CGColorSpaceCreateDeviceRGB(), kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Little, provider, NULL, YES, kCGRenderingIntentDefault);
        UIImage *image = [UIImage imageWithCGImage: cgImage];
        UIImageWriteToSavedPhotosAlbum(image, self_object, nil, nil);
        CGImageRelease(cgImage);
        CFRelease(destSurf);

Answer 1

After combining code from 2 places, I was able to save photo to photo album (with my application in background).

IOSurfaces - Artefacts in video and unable to grab video surfaces

https://github.com/tomcool420/SMFramework/blob/master/SMFScreenCapture.m

Please try out and let me know if it works for you.

-(void)SavePhoto
{
    IOMobileFramebufferConnection connect;
    kern_return_t result;
    IOSurfaceRef screenSurface = NULL;

    io_service_t framebufferService = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("AppleH1CLCD"));
    if(!framebufferService)
        framebufferService = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("AppleM2CLCD"));
    if(!framebufferService)
        framebufferService = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("AppleCLCD"));

    result = IOMobileFramebufferOpen(framebufferService, mach_task_self(), 0, &connect);

    result = IOMobileFramebufferGetLayerDefaultSurface(connect, 0, &screenSurface);

    uint32_t aseed;
    IOSurfaceLock(screenSurface, kIOSurfaceLockReadOnly, &aseed);
    uint32_t width = IOSurfaceGetWidth(screenSurface);
    uint32_t height = IOSurfaceGetHeight(screenSurface);
    //int m_width = 320;
    //int m_height = 480;
    CFMutableDictionaryRef dict;
    int pitch = width*4, size = width*height*4;
    int bPE=4;
    char pixelFormat[4] = {'A','R','G','B'};
    dict = CFDictionaryCreateMutable(kCFAllocatorDefault, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    CFDictionarySetValue(dict, kIOSurfaceIsGlobal, kCFBooleanTrue);
    CFDictionarySetValue(dict, kIOSurfaceBytesPerRow, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &pitch));
    CFDictionarySetValue(dict, kIOSurfaceBytesPerElement, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &bPE));
    CFDictionarySetValue(dict, kIOSurfaceWidth, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &width));
    CFDictionarySetValue(dict, kIOSurfaceHeight, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &height));
    CFDictionarySetValue(dict, kIOSurfacePixelFormat, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, pixelFormat));
    CFDictionarySetValue(dict, kIOSurfaceAllocSize, CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &size));

    IOSurfaceRef destSurf = IOSurfaceCreate(dict);

    void* outAcc;
    IOSurfaceAcceleratorCreate(NULL, 0, &outAcc);

    IOSurfaceAcceleratorTransferSurface(outAcc, screenSurface, destSurf, dict, NULL);

    IOSurfaceUnlock(screenSurface, kIOSurfaceLockReadOnly, &aseed);
    CFRelease(outAcc);

    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, IOSurfaceGetBaseAddress(destSurf), (width * height * 4), NULL);
    CGImageRef cgImage=CGImageCreate(width, height, 8,
                                     8*4, IOSurfaceGetBytesPerRow(destSurf),
                                     CGColorSpaceCreateDeviceRGB(), kCGImageAlphaNoneSkipFirst |kCGBitmapByteOrder32Little,
                                     provider, NULL,
                                     YES, kCGRenderingIntentDefault);
    UIImage *img = [UIImage imageWithCGImage:cgImage];
    UIImageWriteToSavedPhotosAlbum(img, self, nil, nil);

    // MOST RELEVANT PART OF CODE

    //CVPixelBufferCreateWithBytes(NULL, width, height, kCVPixelFormatType_32BGRA, IOSurfaceGetBaseAddress(destSurf), IOSurfaceGetBytesPerRow(destSurf), NULL, NULL, NULL, &sampleBuffer);
}