/**
 图片宽高尺寸限制在200-1024之间，maxSize kb以内
 */
- (NSData *)resetSizeOfImage:(UIImage *)sourceImage maxSize:(NSInteger)maxSize {
    //最终图片data
    __block NSData *finallImageData = UIImageJPEGRepresentation(sourceImage, 1.0);

    //原图宽高比
    CGFloat sourceImageAspectRatio = sourceImage.size.width / sourceImage.size.height;

    CGFloat defaultWidth = sourceImage.size.width;
    CGFloat defaultHeight = sourceImage.size.height;
    CGSize defaultSize = sourceImage.size;
    
    if (defaultWidth > 1024 || defaultHeight > 1024) {
        
        //判断尺寸是否过大
        
        if (defaultWidth > 1024 && defaultWidth > defaultHeight) {
            defaultSize = CGSizeMake(1024, 1024 / sourceImageAspectRatio);
        } else if (defaultHeight > 1024 && defaultWidth < defaultHeight) {
            defaultSize = CGSizeMake(1024 * sourceImageAspectRatio, 1024);
        }
                
    } else if (defaultWidth < 200 || defaultHeight < 200) {
        
        //判断尺寸是否过小
        if (defaultWidth < 200 && defaultWidth < defaultHeight) {
            defaultSize = CGSizeMake(200, 200 / sourceImageAspectRatio);
        } else if (defaultHeight < 200 && defaultWidth > defaultHeight) {
            defaultSize = CGSizeMake(200 * sourceImageAspectRatio, 200);
        }
    }
    
    //先调整分辨率
    UIImage *newImage = [self newSizeImage:defaultSize image:sourceImage];

    finallImageData = UIImageJPEGRepresentation(newImage, 1.0);
        

    //判断当前质量是否满足要求，不满足再进行压缩
    NSUInteger sizeOrigin   = finallImageData.length;//data.length即可得到图片的字节大小
    
    NSUInteger sizeOriginKB = sizeOrigin / 1000;

    if (sizeOriginKB <= maxSize) {
        return finallImageData;
    }
    

    //保存压缩系数
    NSMutableArray *compressionQualityArr = [NSMutableArray array];
    CGFloat avg   = 1.0/250;
    CGFloat value = avg;
    for (int i = 250; i >= 1; i--) {
        value = 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：使用二分法搜索
    finallImageData = [self halfFuntion:compressionQualityArr 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.length == 0) {
        //每次降100分辨率
        CGFloat reduceWidth = 100.0;
        CGFloat reduceHeight = 100.0/sourceImageAspectRatio;
        if (defaultSize.width-reduceWidth <= 0 || defaultSize.height-reduceHeight <= 0) {
            break;
        }
        defaultSize = CGSizeMake(defaultSize.width-reduceWidth, defaultSize.height-reduceHeight);
        UIImage *image = [self newSizeImage:defaultSize
                                      image:[UIImage imageWithData:UIImageJPEGRepresentation(newImage,[[compressionQualityArr lastObject] floatValue])]];
        finallImageData = [self halfFuntion:compressionQualityArr image:image sourceData:UIImageJPEGRepresentation(image,1.0) maxSize:maxSize];
    }
    return finallImageData;
}

#pragma mark - 调整图片分辨率/尺寸（等比例缩放）

- (UIImage *)newSizeImage:(CGSize)size image:(UIImage *)sourceImage {
    CGSize newSize = CGSizeMake(sourceImage.size.width, sourceImage.size.height);
    
    CGFloat tempHeight = newSize.height / size.height;
    CGFloat tempWidth = newSize.width / size.width;
    
    if (tempWidth > 1.0 && tempWidth > tempHeight) {
        newSize = CGSizeMake(sourceImage.size.width / tempWidth, sourceImage.size.height / tempWidth);
    } else if (tempHeight > 1.0 && tempWidth < tempHeight) {
        newSize = CGSizeMake(sourceImage.size.width / tempHeight, sourceImage.size.height / tempHeight);
    } else {
        newSize = size;
    }
    
    UIGraphicsBeginImageContext(newSize);
    [sourceImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

#pragma mark - 二分法
- (NSData *)halfFuntion:(NSArray *)arr image:(UIImage *)image sourceData:(NSData *)finallImageData maxSize:(NSInteger)maxSize {
    NSData *tempData = [NSData data];
    NSUInteger start = 0;
    NSUInteger end = arr.count - 1;
    NSUInteger index = 0;
    
    NSUInteger difference = NSIntegerMax;
    while(start <= end) {
        index = start + (end - start)/2;
        
        finallImageData = UIImageJPEGRepresentation(image,[arr[index] floatValue]);
        
        NSUInteger sizeOrigin = finallImageData.length;
        NSUInteger sizeOriginKB = sizeOrigin / 1024;
        NSLog(@"当前降到的质量：%ld", (unsigned long)sizeOriginKB);
        NSLog(@"\nstart：%zd\nend：%zd\nindex：%zd\n压缩系数：%lf", start, end, (unsigned long)index, [arr[index] floatValue]);
        
        if (sizeOriginKB > maxSize) {
            start = index + 1;
        } else if (sizeOriginKB < maxSize) {
            if (maxSize-sizeOriginKB < difference) {
                difference = maxSize-sizeOriginKB;
                tempData = finallImageData;
            }
            if (index<=0) {
                break;
            }
            end = index - 1;
        } else {
            break;
        }
    }
    return tempData;
}