Handling error for CGBitmapContextCreate

How can I catch or handle an eror that is thrown during the creation of bitmap context? By the way开发者_StackOverflow社区 I know what the error means and I want to use it to create a different context.

Function that throws Error:

CGContextRef ctx = CGBitmapContextCreate(m_PixelBuf,  
                                                 CGImageGetWidth(grayImage),  
                                                 CGImageGetHeight(grayImage),  
                                                 CGImageGetBitsPerComponent(grayImage),
                                                 CGImageGetBytesPerRow(grayImage),  
                                                 CGImageGetColorSpace(grayImage), 
                                                 CGImageGetBitmapInfo(grayImage)
                                                 );

Consol log with the error:

Fri May 13 11:47:21 C.local x[2569] <Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaLast; 616 bytes/row.
Fri May 13 11:47:21 C.local x[2569] <Error>: CGBitmapContextCreateImage: invalid context 0x0

You could check if the context is NULL after trying to create it.