1. #pragma mark - 压缩图片到指定大小(单位KB)
    2. - (NSData *)resetSizeOfImageData:(UIImage *)sourceImage
    4.                          maxSize:(NSInteger)maxSize {
    6.     //先判断当前质量是否满足要求，不满足再进行压缩
    8.     __block NSData *finallImageData = UIImageJPEGRepresentation(sourceImage,1.0);
    10.     NSUInteger sizeOrigin   = finallImageData.length;
    12.     NSUInteger sizeOriginKB = sizeOrigin / 1000;
    16.     if (sizeOriginKB <= maxSize) {
    18.         return finallImageData;
    20.     }
    24.     //获取原图片宽高比
    26.     CGFloat sourceImageAspectRatio = sourceImage.size.width/sourceImage.size.height;
    28.     //先调整分辨率
    30.     CGSize defaultSize = CGSizeMake(1024, 1024/sourceImageAspectRatio);
    32.     UIImage *newImage = [self newSizeImage:defaultSize image:sourceImage];
    36.     finallImageData = UIImageJPEGRepresentation(newImage,1.0);
    40.     //保存压缩系数
    42.     NSMutableArray *compressionQualityArr = [NSMutableArray array];
    44.     CGFloat avg   = 1.0/250;
    46.     CGFloat value = avg;
    48.     for (int i = 250; i >= 1; i--) {
    50.         value = i*avg;
    52.         [compressionQualityArr addObject:@(value)];
    54.     }
    58.     /*
    60.      调整大小
    62.      说明：压缩系数数组compressionQualityArr是从大到小存储。
    64.      */
    66.     //思路：使用二分法搜索
    68.     __block NSData *canCompressMinData = [NSData data];//当无法压缩到指定大小时，用于存储当前能够压缩到的最小值数据。
    70.     [self halfFuntion:compressionQualityArr image:newImage sourceData:finallImageData maxSize:maxSize resultBlock:^(NSData *finallData, NSData *tempData) {
    72.         finallImageData = finallData;
    74.         canCompressMinData = tempData;
    76.     }];
    78.     //如果还是未能压缩到指定大小，则进行降分辨率
    80.     while (finallImageData.length == 0) {
    82.         //每次降100分辨率
    84.         CGFloat reduceWidth = 100.0;
    86.         CGFloat reduceHeight = 100.0/sourceImageAspectRatio;
    88.         if (defaultSize.width-reduceWidth <= 0 || defaultSize.height-reduceHeight <= 0) {
    90.             break;
    92.         }
    94.         defaultSize = CGSizeMake(defaultSize.width-reduceWidth, defaultSize.height-reduceHeight);
    96.         UIImage *image = [self newSizeImage:defaultSize
    98.                                       image:[UIImage imageWithData:UIImageJPEGRepresentation(newImage,[[compressionQualityArr lastObject] floatValue])]];
    100.         [self halfFuntion:compressionQualityArr image:image sourceData:UIImageJPEGRepresentation(image,1.0) maxSize:maxSize resultBlock:^(NSData *finallData, NSData *tempData) {
    102.             finallImageData = finallData;
    104.             canCompressMinData = tempData;
    106.         }];
    108.     }
    110.     //如果分辨率已经无法再降低，则直接使用能够压缩的那个最小值即可
    112.     if (finallImageData.length==0) {
    114.         finallImageData = canCompressMinData;
    116.     }
    118.     return finallImageData;
    120. }
    124. #pragma mark 调整图片分辨率/尺寸（等比例缩放）
    126. ///调整图片分辨率/尺寸（等比例缩放）
    128. - (UIImage *)newSizeImage:(CGSize)size
    130.                     image:(UIImage *)sourceImage {
    132.     CGSize newSize = CGSizeMake(sourceImage.size.width, sourceImage.size.height);
    136.     CGFloat tempHeight = newSize.height / size.height;
    138.     CGFloat tempWidth = newSize.width / size.width;
    142.     if (tempWidth > 1.0 && tempWidth > tempHeight) {
    144.         newSize = CGSizeMake(sourceImage.size.width / tempWidth, sourceImage.size.height / tempWidth);
    146.     } else if (tempHeight > 1.0 && tempWidth < tempHeight) {
    148.         newSize = CGSizeMake(sourceImage.size.width / tempHeight, sourceImage.size.height / tempHeight);
    150.     }
    154.     //    UIGraphicsBeginImageContext(newSize);
    156.     UIGraphicsBeginImageContextWithOptions(newSize, NO, 1);
    158.     [sourceImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    160.     UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    162.     UIGraphicsEndImageContext();
    164.     return newImage;
    166. }
    170. #pragma mark 二分法
    172. ///二分法，block回调中finallData长度不为零表示最终压缩到了指定的大小，如果为零则表示压缩不到指定大小。tempData表示当前能够压缩到的最小值。
    174. - (void)halfFuntion:(NSArray *)arr
    176.               image:(UIImage *)image
    178.          sourceData:(NSData *)finallImageData
    180.             maxSize:(NSInteger)maxSize
    182.         resultBlock:(void(^)(NSData *finallData, NSData *tempData))block {
    184.     NSData *tempData = [NSData data];
    186.     NSUInteger start = 0;
    188.     NSUInteger end = arr.count - 1;
    190.     NSUInteger index = 0;
    194.     NSUInteger difference = NSIntegerMax;
    196.     while(start <= end) {
    198.         index = start + (end - start)/2;
    202.         finallImageData = UIImageJPEGRepresentation(image,[arr[index] floatValue]);
    206.         NSUInteger sizeOrigin = finallImageData.length;
    208.         NSUInteger sizeOriginKB = sizeOrigin / 1000;
    210.         NSLog(@"当前降到的质量：%ld", (unsigned long)sizeOriginKB);
    212.         //        NSLog(@"\nstart：%zd\nend：%zd\nindex：%zd\n压缩系数：%lf", start, end, (unsigned long)index, [arr[index] floatValue]);
    216.         if (sizeOriginKB > maxSize) {
    218.             start = index + 1;
    220.         } else if (sizeOriginKB < maxSize) {
    222.             if (maxSize-sizeOriginKB < difference) {
    224.                 difference = maxSize-sizeOriginKB;
    226.                 tempData = finallImageData;
    228.             }
    230.             if (index<=0) {
    232.                 break;
    234.             }
    236.             end = index - 1;
    238.         } else {
    240.             break;
    242.         }
    244.     }
    246.     NSData *d = [NSData data];
    248.     if (tempData.length==0) {
    250.         d = finallImageData;
    252.     }
    254.     if (block) {
    256.         block(tempData, d);
    258.     }
    260. }