Swift3.0版本二分法压缩模式
// MARK: - 降低质量
func resetSizeOfImageData(source_image: UIImage!, maxSize: Int) -> NSData {
//先判断当前质量是否满足要求，不满足再进行压缩
var finallImageData = UIImageJPEGRepresentation(source_image,1.0)
let sizeOrigin = finallImageData?.count
let sizeOriginKB = sizeOrigin! / 1024
if sizeOriginKB <= maxSize {
return finallImageData! as NSData
}
//先调整分辨率
var defaultSize = CGSize(width: 1024, height: 1024)
let newImage = self.newSizeImage(size: defaultSize, source_image: source_image)
finallImageData = UIImageJPEGRepresentation(newImage,1.0);
//保存压缩系数
let compressionQualityArr = NSMutableArray()
let avg = CGFloat(1.0/250)
var value = avg
var i = 250
repeat {
i -= 1
value = CGFloat(i)*avg
compressionQualityArr.add(value)
} while i >= 1
/*
调整大小
说明：压缩系数数组compressionQualityArr是从大到小存储。
*/
//思路：使用二分法搜索
finallImageData = self.halfFuntion(arr: compressionQualityArr.copy() as! [CGFloat], image: newImage, sourceData: finallImageData!, maxSize: maxSize)
//如果还是未能压缩到指定大小，则进行降分辨率
while finallImageData?.count == 0 {
//每次降100分辨率
if defaultSize.width-100 <= 0 || defaultSize.height-100 <= 0 {
break
}
defaultSize = CGSize(width: defaultSize.width-100, height: defaultSize.height-100)
let image = self.newSizeImage(size: defaultSize, source_image: UIImage.init(data: UIImageJPEGRepresentation(newImage, compressionQualityArr.lastObject as! CGFloat)!)!)
finallImageData = self.halfFuntion(arr: compressionQualityArr.copy() as! [CGFloat], image: image, sourceData: UIImageJPEGRepresentation(image,1.0)!, maxSize: maxSize)
}
return finallImageData! as NSData
}
// MARK: - 调整图片分辨率/尺寸（等比例缩放）
func newSizeImage(size: CGSize, source_image: UIImage) -> UIImage {
var newSize = CGSize(width: source_image.size.width, height: source_image.size.height)
let tempHeight = newSize.height / size.height
let tempWidth = newSize.width / size.width
if tempWidth > 1.0 && tempWidth > tempHeight {
newSize = CGSize(width: source_image.size.width / tempWidth, height: source_image.size.height / tempWidth)
} else if tempHeight > 1.0 && tempWidth < tempHeight {
newSize = CGSize(width: source_image.size.width / tempHeight, height: source_image.size.height / tempHeight)
}
UIGraphicsBeginImageContext(newSize)
source_image.draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage!
}
// MARK: - 二分法
func halfFuntion(arr: [CGFloat], image: UIImage, sourceData finallImageData: Data, maxSize: Int) -> Data? {
var tempFinallImageData = finallImageData
var tempData = Data.init()
var start = 0
var end = arr.count - 1
var index = 0
var difference = Int.max
while start <= end {
index = start + (end - start)/2
tempFinallImageData = UIImageJPEGRepresentation(image, arr[index])!
let sizeOrigin = tempFinallImageData.count
let sizeOriginKB = sizeOrigin / 1024
print("当前降到的质量：(sizeOriginKB)n(index)----(arr[index])")
if sizeOriginKB > maxSize {
start = index + 1
} else if sizeOriginKB < maxSize {
if maxSize-sizeOriginKB < difference {
difference = maxSize-sizeOriginKB
tempData = tempFinallImageData
}
end = index - 1
} else {
break
}
}
return tempData
}
