objective-c – 尝试访问CIFilter的outputImage时出现“无法识别的选择器”

概述我第一次尝试使用Core Image(OS X,10.7.3)并且遇到了一堵砖墙.我确定这是我正在做的傻事,只需要更熟悉框架的人向我指出. 请考虑以下代码(让我们规定imageURL是指向磁盘上JPG的有效文件URL)： CIImage *inputImage = [CIImage imageWithContentsOfURL:imageURL];CIFilter *filter = [CIFi 我第一次尝试使用Core Image(OS X,10.7.3)并且遇到了一堵砖墙.我确定这是我正在做的傻事,只需要更熟悉框架的人向我指出.

请考虑以下代码(让我们规定imageURL是指向磁盘上JPG的有效文件URL)：

CIImage *inputimage = [CIImage imageWithContentsOfURL:imageURL];CIFilter *filter = [CIFilter filterWithname:@"CIAreaAverage" keysAndValues:                                                  kCIInputimageKey,inputimage,kCIinputExtentKey,[inputimage valueForKey:@"extent"],nil];CIImage *outputimage = (CIImage *)[filter valueForKey:@"outputimage"];

运行此代码时,最后一行触发：

0   CoreFoundation                      0x00007fff96c2efc6 __exceptionPreprocess + 1981   libobjc.A.dylib                     0x00007fff9153cd5e objc_exception_throw + 432   CoreFoundation                      0x00007fff96cbb2ae -[NSObject doesNotRecognizeSelector:] + 1903   CoreFoundation                      0x00007fff96c1be73 ___forwarding___ + 3714   CoreFoundation                      0x00007fff96c1bc88 _CF_forwarding_prep_0 + 2325   CoreImage                           0x00007fff8f03c38d -[CIAreaAverage outputimage] + 526   Foundation                          0x00007fff991d8384 _NSGetUsingkeyvalueGetter + 627   Foundation                          0x00007fff991d8339 -[NSObject(NSkeyvalueCoding) valueForKey:] + 392

现在,核心图像过滤器参考清楚地指出CIAreaAverage“返回包含感兴趣区域的平均颜色的单像素图​​像.”实际上,当我在调试器中检查过滤器属性时(在尝试valueForKey：call之前),更令人困惑的是：

(lldb) po [filter attributes](ID)  = 0x00007fb3e3ef0e00 {    CIAttributeDescription = "Calculates the average color for the specifIEd area in an image,returning the result in a pixel.";    CIAttributeFilterCategorIEs =     (        CIcategoryReduction,CIcategoryVIDeo,CIcategoryStillimage,CIcategoryBuiltIn    );    CIAttributeFilterdisplayname = "Area Average";    CIAttributeFiltername = CIAreaAverage;    CIAttributeReferencedocumentation = "http://developer.apple.com/cgi-bin/apple_ref.cgi?apple_ref=//apple_ref/doc/filter/ci/CIAreaAverage";    inputExtent =     {        CIAttributeClass = CIVector;        CIAttributeDefault = "[0 0 640 80]";        CIAttributeDescription = "A rectangle that specifIEs the subregion of the image that you want to process.";        CIAttributedisplayname = Extent;        CIAttributeType = CIAttributeTypeRectangle;        CiuiParameterSet = CiuiSetBasic;    };    inputimage =     {        CIAttributeClass = CIImage;        CIAttributeDescription = "The image to process.";        CIAttributedisplayname = Image;        CiuiParameterSet = CiuiSetBasic;    };    outputimage =     {        CIAttributeClass = CIImage;    };}

那里有outputimage – 以CIImage类型给出！

那么,我做错了什么？我见过的所有文档和教程都表明-valueForKey：是访问属性的正确方法,包括outputimage.

解决方法 我相信你的范围是罪魁祸首(不管它多么奇怪).当我将范围更改为CIVector *时,它可以工作.

NSURL *imageURL = [NSURL fileURLWithPath:@"/Users/davID/Desktop/vIDeo.png"];CIImage *inputimage = [CIImage imageWithContentsOfURL:imageURL];CIFilter *filter = [CIFilter filterWithname:@"CIAreaAverage"];[filter setValue:inputimage forKey:kCIInputimageKey];CGRect inputExtent = [inputimage extent];CIVector *extent = [CIVector vectorWithX:inputExtent.origin.x                                       Y:inputExtent.origin.y                                       Z:inputExtent.size.wIDth                                       W:inputExtent.size.height];[filter setValue:extent forKey:kCIinputExtentKey];CIImage *outputimage = [filter valueForKey:@"outputimage"];

[inputimage extent]返回一个CGRect,但显然CIVector *效果更好.

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