Swift图片选择器，对图片占用内存进行了优化 //根据宽度计算高度 let height = width * size.height / size.width //按照宽高比绘制一张新的图片 let currentSize = CGSize(width: width, height: height) UIGraphicsBeginImageContext(currentSize) drawInRect(CGRect(origin: CGPointZero, size: currentSize)) let newImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return newImage