swift獲取圖片像素顏色值

extension UIImage{ /** 獲取圖片中的像素顏色值 - parameter pos: 圖片中的位置 - returns: 顏色值 */ func getPixelColor(pos:CGPoint)->(alpha: CGFloat, red: CGFloat, green: CGFloat,blue:CGFloat){ let pixelData=CGDataProviderCopyData(CGImageGetDataProvider(self.CGImage)) let data:UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData) let pixelInfo: Int = ((Int(self.size.width) * Int(pos.y)) + Int(pos.x)) * 4 let r = CGFloat(data[pixelInfo]) / CGFloat(255.0) let g = CGFloat(data[pixelInfo+1]) / CGFloat(255.0) let b = CGFloat(data[pixelInfo+2]) / CGFloat(255.0) let a = CGFloat(data[pixelInfo+3]) / CGFloat(255.0) return (a,r,g,b) } }