<1>圖片壓縮
這個三個方法環環緊扣，使用二分法迅速壓縮圖片大小，試了下，iPad的話400KB差不多圖片不虛，小於200就會虛的很
#pragma mark - 圖片壓縮
+ (NSData *)resetSizeOfImageData:(UIImage *)sourceImage maxSize:(NSInteger)maxSize {
//先判斷當前質量是否滿足要求，不滿足再進行壓縮
__block NSData *finallImageData = UIImageJPEGRepresentation(sourceImage,1.0);
NSUInteger sizeOrigin = finallImageData.length;
NSUInteger sizeOriginKB = sizeOrigin / 1000;
if (sizeOriginKB <= maxSize) {
return finallImageData;
}
//獲取原圖片寬高比
CGFloat sourceImageAspectRatio = sourceImage.size.width/sourceImage.size.height;
//先調整分辨率
CGSize defaultSize = CGSizeMake(1024, 1024/sourceImageAspectRatio);
UIImage *newImage = [self newSizeImage:defaultSize image:sourceImage];
finallImageData = UIImageJPEGRepresentation(newImage,1.0);
//保存壓縮係數
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)];
}
/*
調整大小
說明：壓縮係數數組compressionQualityArr是從大到小存儲。
*/
//思路：使用二分法搜索
finallImageData = [self halfFuntion:compressionQualityArr image:newImage sourceData:finallImageData maxSize:maxSize];
//如果還是未能壓縮到指定大小，則進行降分辨率
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 調整圖片分辨率/尺寸（等比例縮放）
+ (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);
[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(@"當前降到的質量：%ld", (unsigned long)sizeOriginKB);
NSLog(@"\nstart：%zd\nend：%zd\nindex：%zd\n壓縮係數：%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;
}
<2>圖片裁剪，單獨使用
#pragma ---圖片裁剪
//裁剪image大小
-(UIImage*)OriginImage:(UIImage *)image scaleToSize:(CGSize)size{
UIGraphicsBeginImageContext(size); //size 爲CGSize類型，即你所需要的圖片尺寸
[image drawInRect:CGRectMake(0, 0, size.width, size.height)];
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage; //返回的就是已經改變的圖片
}