压缩图片到指定大小(单位KB)(不失真)
#pragma mark - 压缩图片到指定大小(单位KB)
- (NSData *)resetSizeOfImageData:(UIImage *)sourceImage
maxSize:(NSInteger)maxSize {
//先判断当前质量是否满足要求，不满足再进行压缩
__block NSData *finallImageData = UIImageJPEGRepresentation(sourceImage,1.0);
NSUInteger sizeOrigin = finallImageData.length;
NSUInteger sizeOriginKB = sizeOrigin / 1000;
if (sizeOriginKB <= maxSize) {
return finallImageData;
}
//获取原图片宽高比
CGFloat sourceImageAspectRatio = sourceImage.size.width/sourceImage.size.height;
//先调整分辨率
CGSize defaultSize = CGSizeMake(1024, 1024/sourceImageAspectRatio);
UIImage *newImage = [self newSizeImage:defaultSize image:sourceImage];
finallImageData = UIImageJPEGRepresentation(newImage,1.0);
//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
__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。
[self halfFuntion:compressionQualityArr image:newImage sourceData:finallImageData maxSize:maxSize resultBlock:^(NSData *finallData, NSData *tempData) {
finallImageData = finallData;
canCompressMinData = tempData;
}];
//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])]];
[self halfFuntion:compressionQualityArr image:image sourceData:UIImageJPEGRepresentation(image,1.0) maxSize:maxSize resultBlock:^(NSData *finallData, NSData *tempData) {
finallImageData = finallData;
canCompressMinData = tempData;
}];
}
//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
if (finallImageData.length==0) {
finallImageData = canCompressMinData;
}
return finallImageData;
}
#pragma mark 调整图片分辨率/尺寸（等比例缩放）
///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);
}
// UIGraphicsBeginImageContext(newSize);
UIGraphicsBeginImageContextWithOptions(newSize, NO, 1);
[sourceImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
#pragma mark 二分法
///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。
- (void)halfFuntion:(NSArray *)arr
image:(UIImage *)image
sourceData:(NSData *)finallImageData
maxSize:(NSInteger)maxSize
resultBlock:(void(^)(NSData *finallData, NSData *tempData))block {
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 / 1000;
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;
}
}
NSData *d = [NSData data];
if (tempData.length==0) {
d = finallImageData;
}
if (block) {
block(tempData, d);
}
}
