截屏代码在游戏界面上失效！！！！！！！！！！！！！

技能讨论
#1

如下截代码对于某些游戏的界面截出来的是黑屏，大概是什么原因，其他的都可以正常截出来？

//截屏
int fb_open_test(NSString *picpath)
{
int ret;
IOMobileFramebufferConnection connect;
kern_return_t result;
void *screenSurface;

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);

printf("width====%d\n",width);
printf("height====%d\n",height);

CFMutableDictionaryRef dict;
int pitch = width*4, size = 4*width*height;
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);
IOSurfaceAcceleratorRef outAcc;
IOSurfaceAcceleratorCreate(NULL, 0, &outAcc);

//CFDictionaryRef ed = (__bridge CFDictionaryRef)[NSDictionary dictionaryWithObjectsAndKeys: nil];
CFDictionaryRef ed = (CFDictionaryRef)[NSDictionary dictionaryWithObjectsAndKeys: nil];

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

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];
CGImageRelease(cgImage);


//UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

NSData* data =  UIImagePNGRepresentation(image);
//BOOL success=[data writeToFile:@"/var/mobile/shot1.png" atomically:YES];
BOOL success=[data writeToFile:picpath atomically:YES];
if (success==true)
{
    printf("writeToFile success\n");
    ret = 0;
}
else
{
    printf("writeToFile failed\n");
    ret = 1;
}
CFRelease(destSurf);
return ret;

}