判斷是否為gif/png圖片的正確姿勢

判斷是否為gif/png圖片的正確姿勢

1.在能取到圖片后綴的前提下

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//假設這是一個網絡獲取的URL NSString?*path?=?@"http://pic3.nipic.com/20090709/2893198_075124038_2.gif"; //?判斷是否為gif NSString?*extensionName?=?path.pathExtension; if?([extensionName.lowercaseString?isEqualToString:@"gif"])?{ ????//是gif圖片 }?else?{ ????//不是gif圖片 ?}

2.不知道時.其實就是取出圖片數據的第一個字節, 就可以判斷出圖片的真實類型那該怎么做呢如下:

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//通過圖片Data數據第一個字節?來獲取圖片擴展名 -?(NSString?*)contentTypeForImageData:(NSData?*)data?{ ????uint8_t?c; ????[data?getBytes:&c?length:1]; ????switch?(c)?{ ????????case?0xFF: ????????????return?@"jpeg"; ????????case?0x89: ????????????return?@"png"; ????????case?0x47: ????????????return?@"gif"; ????????case?0x49: ????????case?0x4D: ????????????return?@"tiff"; ????????case?0x52: ????????????if?([data?length]?<?12)?{ ????????????????return?nil; ????????????} ????????????NSString?*testString?=?[[NSString?alloc]?initWithData:[data?subdataWithRange:NSMakeRange(0,?12)]?encoding:NSASCIIStringEncoding]; ????????????if?([testString?hasPrefix:@"RIFF"]?&&?[testString?hasSuffix:@"WEBP"])?{ ????????????????return?@"webp"; ????????????} ????????????return?nil; ????} ????return?nil; }

其實圖片數據的第一個字節是固定的,一種類型的圖片第一個字節就是它的標識, 我們來調用一下這個方法:

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//假設這是一個網絡獲取的URL NSString?*path?=?@"http://pic.rpgsky.net/images/2016/07/26/3508cde5f0d29243c7d2ecbd6b9a30f1.png"; NSData?*data?=?[NSData?dataWithContentsOfURL:[NSURL?URLWithString:path]]; //調用獲取圖片擴展名 NSString?*string?=?[self?contentTypeForImageData:data]; //輸出結果為?png NSLog(@"%@",string);