利用UIImageJPEGRepresentation与UIGraphicsBeginImageContext进行图片压缩的简单比较

转自：http://www.it165.net/pro/html/201405/14050.html

利用UIImageJPEGRepresentation与UIGraphicsBeginImageContext进行图片压缩的简单比较

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01.UIImage *image01 = [UIImage imageNamed:@"002.png"];//原图

02. 

03.NSData *dataOf02 =UIImageJPEGRepresentation(image01, 0.5);//压缩图片内容，不影响图片的size，得到一个原大小，但更模糊的图片。

04.UIImage *image02 = [UIImage imageWithData:dataOf02];//压缩图02

05. 

06.UIImage *image03 = [self makeThumbnailFromImage:image01 scale:0.5];//压缩图03

07.NSLog(@"001===%@",NSStringFromCGSize(image01.size));

08.NSLog(@"002===%@",NSStringFromCGSize(image02.size));

09.NSLog(@"003===%@",NSStringFromCGSize(image03.size));

10. 

11.NSData *data001 = UIImageJPEGRepresentation(image01, 1.0);

12.NSData *data002 = UIImageJPEGRepresentation(image02, 1.0);

13.NSData *data003 = UIImageJPEGRepresentation(image03, 1.0);

14. 

15.NSLog(@"002.lenght===%d",data001.length);

16.NSLog(@"002.lenght===%d",data002.length);

17.NSLog(@"003.lenght===%d",data003.length);

18. 

19.//看一下效果

20.UIImageView *imageView01 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, image01.size.width, image01.size.height)];

21.imageView01.image = image01;

22.[self.view addSubview:imageView01];

23. 

24.UIImageView *imageView02 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 100, image02.size.width, image02.size.height)];

25.imageView02.image = image02;

26.[self.view addSubview:imageView02];

27. 

28.UIImageView *imageView03 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 200, image03.size.width, image03.size.height)];

29.imageView03.image = image03;

30.[self.view addSubview:imageView03];

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01.//手动实现图片压缩，可以写到分类里，封装成常用方法。按照大小进行比例压缩，改变了图片的size。

02.- (UIImage *)makeThumbnailFromImage:(UIImage *)srcImage scale:(double)imageScale {

03.UIImage *thumbnail = nil;

04.CGSize imageSize = CGSizeMake(srcImage.size.width * imageScale, srcImage.size.height * imageScale);

05.if (srcImage.size.width != imageSize.width || srcImage.size.height != imageSize.height)

06.{

07.UIGraphicsBeginImageContext(imageSize);

08.CGRect imageRect = CGRectMake(0.0, 0.0, imageSize.width, imageSize.height);

09.[srcImage drawInRect:imageRect];

10.thumbnail = UIGraphicsGetImageFromCurrentImageContext();

11.UIGraphicsEndImageContext();

12.}

13.else

14.{

15.thumbnail = srcImage;

16.}

17.return thumbnail;

18.}

效果图：

转自：http://www.th7.cn/Program/IOS/201406/214037.shtml

UIImage *image = [[UIImagealloc]initWithCGImage:imageReference scale:imageScale orientation:imageOritation];

//创建缩略图

UIImage *newImage = [LYGAllPhtotViewController thumbnilWithImageWithoutScale:imagesize:CGSizeMake(image.size.width/2,image.size.height/2)];

                            

[_phtotArr addObject:newImage];

image = nil;

//保持原来的长宽比，生成一个缩略图

+ (UIImage *)thumbnailWithImageWithoutScale:(UIImage *)image size:(CGSize)asize

{

UIImage *newimage;

if (nil == image) {

newimage = nil;

}

else{

CGSize oldsize = image.size;

CGRect rect;

if (asize.width/asize.height > oldsize.width/oldsize.height) {

rect.size.width = asize.height*oldsize.width/oldsize.height;

rect.size.height = asize.height;

rect.origin.x = (asize.width - rect.size.width)/2;

rect.origin.y = 0;

}

else{

rect.size.width = asize.width;

rect.size.height = asize.width*oldsize.height/oldsize.width;

rect.origin.x = 0;

rect.origin.y = (asize.height - rect.size.height)/2;

}

//开始绘图生成水印图片

UIGraphicsBeginImageContext(asize);

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);

UIRectFill(CGRectMake(0, 0, asize.width, asize.height));//clear background

[image drawInRect:rect];

newimage = UIGraphicsGetImageFromCurrentImageContext();

//结束绘图

UIGraphicsEndImageContext();

}

return newimage;

}

//自动缩放到指定大小

+ (UIImage *)thumbnailWithImage:(UIImage *)image size:(CGSize)asize

{

UIImage *newimage;

if (nil == image) {

newimage = nil;

}

else{

UIGraphicsBeginImageContext(asize);

[image drawInRect:CGRectMake(0, 0, asize.width, asize.height)];

newimage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

}

return newimage;

}

缩略前后图片对照：