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
01.
UIImage *image01 = [UIImage imageNamed:@"002.png"];//原图
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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
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UIImage *image03 = [self makeThumbnailFromImage:image01 scale:0.5];//压缩图03
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NSLog(@"001===%@",NSStringFromCGSize(image01.size));
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NSLog(@"002===%@",NSStringFromCGSize(image02.size));
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NSLog(@"003===%@",NSStringFromCGSize(image03.size));
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NSData *data001 = UIImageJPEGRepresentation(image01, 1.0);
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NSData *data002 = UIImageJPEGRepresentation(image02, 1.0);
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NSData *data003 = UIImageJPEGRepresentation(image03, 1.0);
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NSLog(@"002.lenght===%d",data001.length);
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NSLog(@"002.lenght===%d",data002.length);
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NSLog(@"003.lenght===%d",data003.length);
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//看一下效果
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UIImageView *imageView01 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, image01.size.width, image01.size.height)];
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imageView01.image = image01;
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[self.view addSubview:imageView01];
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UIImageView *imageView02 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 100, image02.size.width, image02.size.height)];
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imageView02.image = image02;
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[self.view addSubview:imageView02];
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UIImageView *imageView03 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 200, image03.size.width, image03.size.height)];
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imageView03.image = image03;
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[self.view addSubview:imageView03];
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。
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- (UIImage *)makeThumbnailFromImage:(UIImage *)srcImage scale:(double)imageScale {
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UIImage *thumbnail = nil;
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CGSize imageSize = CGSizeMake(srcImage.size.width * imageScale, srcImage.size.height * imageScale);
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if (srcImage.size.width != imageSize.width || srcImage.size.height != imageSize.height)
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{
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UIGraphicsBeginImageContext(imageSize);
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CGRect imageRect = CGRectMake(0.0, 0.0, imageSize.width, imageSize.height);
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[srcImage drawInRect:imageRect];
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thumbnail = UIGraphicsGetImageFromCurrentImageContext();
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UIGraphicsEndImageContext();
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}
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else
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{
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thumbnail = srcImage;
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}
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return thumbnail;
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}
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：
