我正在尝试从iPhone获取EXIF数据来计算亮度。我需要访问两个特定的NSNumber的ExifExposureTime和ExifISOSpeed才能转换为浮点数,但当我尝试将它们转换为浮点数时,我收到此错误:
“2011-04-21 17:38:31.776 POP [11910:207] - [__ NSCFArray floatValue]:无法识别的选择器发送到实例0x4b48f70 2011-04-21 17:38:31.777 POP [11910:207] * 由于未捕获的异常'NSInvalidArgumentException'而终止应用程序,原因:' - [__ NSCFArray floatValue]:无法识别的选择器发送到实例0x4b48f70' “
我遗失了一些愚蠢的错误吗?请告诉我。以下是我的代码:
-(IBAction)getDataOne:(id)sender {
NSString *aPath = [[NSBundle mainBundle] pathForResource:@"IMG_0062" ofType:@"JPG"];
NSURL *url = [NSURL fileURLWithPath:aPath];
CGImageSourceRef sourceRef = CGImageSourceCreateWithURL((CFURLRef)url, NULL);
NSDictionary *immutableMetadata = (NSDictionary *) CGImageSourceCopyPropertiesAtIndex(sourceRef,0,NULL);
NSDictionary *exifDic = [immutableMetadata objectForKey:(NSString *)kCGImagePropertyExifDictionary];
NSNumber *ExifApertureValue = [exifDic objectForKey:(NSString*)kCGImagePropertyExifApertureValue];
NSNumber *ExifShutterSpeed = [exifDic objectForKey:(NSString*)kCGImagePropertyExifShutterSpeedValue];
NSNumber *ExifExposureTime = [exifDic objectForKey:(NSString*)kCGImagePropertyExifExposureTime];
NSNumber *ExifFStop = [exifDic objectForKey:(NSString*)kCGImagePropertyExifFNumber];
NSNumber *ExifISOSpeed = [exifDic objectForKey:(NSString*)kCGImagePropertyExifISOSpeedRatings];
NSLog(@"ExifApertureValue : %@ \n",ExifApertureValue);
NSLog(@"ExifShutterSpeed : %@ \n",ExifShutterSpeed);
NSLog(@"ExifExposureTime : %@ \n",ExifExposureTime);
NSLog(@"ExifFStop : %@ \n",ExifFStop);
NSLog(@"ExifISOSpeed : %@ \n",ExifISOSpeed);
float brightness, T, ISO;
float K = 12.0;
float A2 = 7.84;
T = [ExifExposureTime floatValue];
ISO = [ExifISOSpeed floatValue];
brightness = (A2 * K) / (T * ISO);
[summaryViewController imageOneSuccess];
[ExifApertureValue release];
[ExifShutterSpeed release];
[ExifExposureTime release];
[ExifFStop release];
[ExifISOSpeed release];
}
以下是这5个NSLOG语句中的输出,表明存储了有效值:
2011-04-21 18:05:12.318 POP[12051:207] ExifApertureValue : 2.526069
2011-04-21 18:05:12.319 POP[12051:207] ExifShutterSpeed : 4.915926
2011-04-21 18:05:12.321 POP[12051:207] ExifExposureTime : 0.03333334
2011-04-21 18:05:12.323 POP[12051:207] ExifFStop : 2.4
2011-04-21 18:05:12.324 POP[12051:207] ExifISOSpeed : (
640
)
更新:我正在查看我的输出,并注意到ExifISOSpeed打印的很奇怪:
(
640
)
格式。这就是我转换成浮动时的问题,但有人知道为什么它会以这种方式输出吗?我能够使用if语句并确定它是否大于0所以我能够将其视为数字。
答案 0 :(得分:2)
看起来ExifISOSpeed
是NSArray
,而不是NSNumber
。我会回顾文档;也许有一个原因让你从字典中得到一个数组。
试试这个:
ISO = [(NSNumber *)[ExifISOSpeed objectAtIndex:0] floatValue];
答案 1 :(得分:1)
ExifISOSpeed
是NSArray
而不是NSNumber
。
尝试:
NSNumber *ExifISOSpeed = [[exifDic objectForKey:(NSString*)kCGImagePropertyExifISOSpeedRatings] objectAtIndex:0];