在Swift ios中使用vImageBuffer_initWithCGImage时，“致命错误:在打开可选值时意外发现nil”

I'm working in Swift iOS8 and trying to convert UIImage to vImage_Buffer to perform manipulations using Accelerate.framework. I'm trying to use vImageBuffer_initWithCGImage for conversion, here is the code that I tried:I'm working in Swift iOS8 and trying to convert