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//通过ALAsset获取相对应的资源，获取图片的等比缩略图，原图的等比缩略
CGImageRef ratioThum = [asset aspectRatioThumbnail];
//获取相片的缩略图，该缩略图是相册中每张照片的poster图
CGImageRef thum = [asset thumbnail];
UIImage* rti = [UIImage imageWithCGImage:ratioThum];
UIImage* ti = [UIImage imageWithCGImage:thum];
UIImageView* v1 = [[UIImageView alloc]initWithFrame:CGRectMake(20, 100, 120, 200)];
v1.image = rti;
v1.contentMode = UIViewContentModeScaleAspectFit;
UIImageView* v2 = [[UIImageView alloc]initWithFrame:CGRectMake(180, 100, 120, 200)];
v2.image = ti;
v2.contentMode = UIViewContentModeScaleAspectFit;
[self.view addSubview:v1];
[self.view addSubview:v2];
左侧为等比缩略图效果，右侧为poster效果的缩略图
UIImage* ni = [UIImage imageNamed:@"new.png"]; //修改指定路径的图片资源内容，替换掉原来的内容 [asset setImageData:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) { NSLog(@"new:%@",assetURL); }]; //根据给定的图片内容，重新生成一张新图 [asset writeModifiedImageDataToSavedPhotosAlbum:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) { NSLog(@"new:%@",assetURL); }]; //获取资源图片的详细资源信息 ALAssetRepresentation* representation = [asset defaultRepresentation]; //获取资源图片的长宽 CGSize dimension = [representation dimensions]; //获取资源图片的高清图 [representation fullResolutionImage]; //获取资源图片的全屏图 [representation fullScreenImage]; //获取资源图片的名字 NSString* filename = [representation filename]; NSLog(@"filename:%@",filename); //缩放倍数 [representation scale]; //图片资源容量大小 [representation size]; //图片资源原数据 [representation metadata]; //旋转方向 [representation orientation]; //资源图片url地址，该地址和ALAsset通过ALAssetPropertyAssetURL获取的url地址是一样的 NSURL* url = [representation url]; NSLog(@"url:%@",url); //资源图片uti，唯一标示符 NSLog(@"uti:%@",[representation UTI]);
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原文地址：http://www.cnblogs.com/nonato/p/4402253.html
