实现代码
Swift3.0之前旧版本压缩模式
// MARK: - 降低质量
func resetSizeOfImageData(source_image: UIImage, maxSize: Int) -> NSData {
//先调整分辨率
var newSize = CGSize(width: source_image.size.width, height: source_image.size.height)
let tempHeight = newSize.height / 1024
let tempWidth = newSize.width / 1024
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.drawAsPatternInRect(CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
//先判断当前质量是否满足要求，不满足再进行压缩
var finallImageData = UIImageJPEGRepresentation(newImage,1.0)
let sizeOrigin = Int64((finallImageData?.length)!)
let sizeOriginKB = Int(sizeOrigin / 1024)
if sizeOriginKB <= maxSize {
return finallImageData!
}
//保存压缩系数
let compressionQualityArr = NSMutableArray()
let avg = CGFloat(1.0/250)
var value = avg
for var i = 250; i>=1; i-- {
value = CGFloat(i)*avg
compressionQualityArr.addObject(value)
}
//调整大小
//说明：压缩系数数组compressionQualityArr是从大到小存储。
//思路：折半计算，如果中间压缩系数仍然降不到目标值maxSize，则从后半部分开始寻找压缩系数；反之从前半部分寻找压缩系数
finallImageData = UIImageJPEGRepresentation(newImage, CGFloat(compressionQualityArr[125] as! NSNumber))
if Int(Int64((UIImageJPEGRepresentation(newImage, CGFloat(compressionQualityArr[125] as! NSNumber))?.length)!)/1024) > maxSize {
//拿到最初的大小
finallImageData = UIImageJPEGRepresentation(newImage, 1.0)
//从后半部分开始
for idx in 126..<250 {
let value = compressionQualityArr[idx]
let sizeOrigin = Int64((finallImageData?.length)!)
let sizeOriginKB = Int(sizeOrigin / 1024)
print("当前降到的质量：(sizeOriginKB)")
if sizeOriginKB > maxSize {
print("(idx)----(value)")
finallImageData = UIImageJPEGRepresentation(newImage, CGFloat(value as! NSNumber))
} else {
break
}
}
} else {
//拿到最初的大小
finallImageData = UIImageJPEGRepresentation(newImage, 1.0)
//从前半部分开始
for idx in 0..<125 {
let value = compressionQualityArr[idx]
let sizeOrigin = Int64((finallImageData?.length)!)
let sizeOriginKB = Int(sizeOrigin / 1024)
print("当前降到的质量：(sizeOriginKB)")
if sizeOriginKB > maxSize {
print("(idx)----(value)")
finallImageData = UIImageJPEGRepresentation(newImage, CGFloat(value as! NSNumber))
} else {
break
}
}
}
return finallImageData!
}
