發送CGImageRef作爲輸出參數

Question

我需要捕獲移動窗口。由於窗口正在我想捕捉它在主線程：

void MacRenderer::captureImageImpl(const CGRect& captureRect, const CGWindowID windowId, CGImageRef* img) 
{ 
    *img = CGWindowListCreateImage(captureRect, kCGWindowListOptionIncludingWindow, windowId, kCGWindowImageBoundsIgnoreFraming); //EXC_BAD_ACCESS 
} 

void MacRenderer::captureWindow(CGWindowID windowId, unsigned char** bgraData, int* width, int* height, int* bytesPerRow, NSRect captureRect) 
{ 
    CGImageRef* windowImage; 

    dispatch_sync(dispatch_get_main_queue(), ^{ 
     captureImageImpl(captureCGRect, windowId, windowImage); 
    }); 

    //Use windowImage ... 
} 

我對img地址越來越EXC_BAD_ACCESS。爲什麼和什麼是解決方案？謝謝！

Answer 1

void MacRenderer::captureWindow(CGWindowID windowId, unsigned char** bgraData, int* width, int* height, int* bytesPerRow, NSRect captureRect) 
{ 
    __block CGImageRef windowImage; 

    dispatch_sync(dispatch_get_main_queue(), ^{ 
     captureImageImpl(captureCGRect, windowId, &windowImage); 
    }); 

    //Use windowImage ... 
}