ALAsset和ALAssetRepresentation詳解

ALAsset類表明相冊中的每一個資源文件，能夠經過它獲取資源文件的相關信息還能修改和新建資源文件，ALAssetRepresentation類表明相冊中每一個資源文件的詳細信息，能夠經過它獲取資源的大小，名字，路徑等詳細信息。

 

                        //經過ALAsset獲取相對應的資源，獲取圖片的等比縮略圖，原圖的等比縮略
                        CGImageRef ratioThum = [asset aspectRatioThumbnail];
                        //獲取相片的縮略圖，該縮略圖是相冊中每張照片的poster圖
                        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];

 

左側爲等比縮略圖效果，右側爲poster效果的縮略圖

                        UIImage* ni = [UIImage imageNamed:@"new.png"];
                        //修改指定路徑的圖片資源內容，替換掉原來的內容
                        [asset setImageData:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {
                            NSLog(@"new:%@",assetURL);
                        }];
                        //根據給定的圖片內容，從新生成一張新圖
                        [asset writeModifiedImageDataToSavedPhotosAlbum:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {
                            NSLog(@"new:%@",assetURL);
                        }];
                        //獲取資源圖片的詳細資源信息
                        ALAssetRepresentation* representation = [asset defaultRepresentation];
                        //獲取資源圖片的長寬
                        CGSize dimension = [representation dimensions];
                        //獲取資源圖片的高清圖
                        [representation fullResolutionImage];
                        //獲取資源圖片的全屏圖
                        [representation fullScreenImage];
                        //獲取資源圖片的名字
                        NSString* filename = [representation filename];
                        NSLog(@"filename:%@",filename);
                        //縮放倍數
                        [representation scale];
                        //圖片資源容量大小
                        [representation size];
                        //圖片資源原數據
                        [representation metadata];
                        //旋轉方向
                        [representation orientation];
                        //資源圖片url地址，該地址和ALAsset經過ALAssetPropertyAssetURL獲取的url地址是同樣的
                        NSURL* url = [representation url];
                        NSLog(@"url:%@",url);
                        //資源圖片uti，惟一標示符
                        NSLog(@"uti:%@",[representation UTI]);