【发布时间】：2025-11-26 07:45:01
【问题描述】：
首先声明：我是 Cocoa 和 Objective-C 的新手。我正在尝试学习使用 Cocoa 和 Opencv，所以我不必处理 Qt。因此，如果有更简单的方法来实现我正在尝试做的事情，我会欢迎任何提示。另外，如果这个问题已经得到解答，如果有人能指出我的答案，我将不胜感激。
我正在使用这篇文章中的代码：NSImage to cv::Mat and vice versa 尝试将我的 NSImage 转换为 Mat 并返回。问题是，我总是最终将无法识别的选择器发送到实例错误。据我了解，此错误是在调用不存在的方法时引发的。但是我调用的方法确实存在。我在这里完全不知所措，非常感谢您对愚蠢的话语的帮助。该代码与上面链接的帖子完全相同。错误如下：
2013-08-15 17:24:52.554 Espejismo[2368:303] -[NSImage CVMat]: unrecognized selector sent to instance 0x1020198d0
2013-08-15 17:25:03.969 Espejismo[2368:303] An uncaught exception was raised
2013-08-15 17:25:03.969 Espejismo[2368:303] -[NSImage CVMat]: unrecognized selector sent to instance 0x1020198d0
2013-08-15 17:25:03.972 Espejismo[2368:303] (
0 CoreFoundation 0x00007fff93e76b06 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff97e0c3f0 objc_exception_throw + 43
2 CoreFoundation 0x00007fff93f0d40a -[NSObject(NSObject) doesNotRecognizeSelector:] + 186
3 CoreFoundation 0x00007fff93e6502e ___forwarding___ + 414
4 CoreFoundation 0x00007fff93eaadad __forwarding_prep_1___ + 237
5 Espejismo 0x000000010000209e -[TestView initWithFrame:] + 334
6 AppKit 0x00007fff942c00a3 -[NSCustomView nibInstantiateWithObjectInstantiator:] + 657
7 AppKit 0x00007fff9429f625 -[NSIBObjectData instantiateObject:] + 266
8 AppKit 0x00007fff9429edf7 -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] + 337
9 AppKit 0x00007fff9427e11d loadNib + 317
10 AppKit 0x00007fff9427d649 +[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:] + 219
11 AppKit 0x00007fff9427d47e -[NSBundle(NSNibLoading) loadNibNamed:owner:topLevelObjects:] + 200
12 AppKit 0x00007fff9427d25e +[NSBundle(NSNibLoading) loadNibNamed:owner:] + 360
13 AppKit 0x00007fff942799ff NSApplicationMain + 398
14 Espejismo 0x0000000100001112 main + 34
15 libdyld.dylib 0x00007fff922077e1 start + 0
)
2013-08-15 17:25:03.973 Espejismo[2368:303] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSImage CVMat]: unrecognized selector sent to instance 0x1020198d0'
*** First throw call stack:
(
0 CoreFoundation 0x00007fff93e76b06 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff97e0c3f0 objc_exception_throw + 43
2 CoreFoundation 0x00007fff93f0d40a -[NSObject(NSObject) doesNotRecognizeSelector:] + 186
3 CoreFoundation 0x00007fff93e6502e ___forwarding___ + 414
4 CoreFoundation 0x00007fff93eaadad __forwarding_prep_1___ + 237
5 Espejismo 0x000000010000209e -[TestView initWithFrame:] + 334
6 AppKit 0x00007fff942c00a3 -[NSCustomView nibInstantiateWithObjectInstantiator:] + 657
7 AppKit 0x00007fff9429f625 -[NSIBObjectData instantiateObject:] + 266
8 AppKit 0x00007fff9429edf7 -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] + 337
9 AppKit 0x00007fff9427e11d loadNib + 317
10 AppKit 0x00007fff9427d649 +[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:] + 219
11 AppKit 0x00007fff9427d47e -[NSBundle(NSNibLoading) loadNibNamed:owner:topLevelObjects:] + 200
12 AppKit 0x00007fff9427d25e +[NSBundle(NSNibLoading) loadNibNamed:owner:] + 360
13 AppKit 0x00007fff942799ff NSApplicationMain + 398
14 Espejismo 0x0000000100001112 main + 34
15 libdyld.dylib 0x00007fff922077e1 start + 0
)
libc++abi.dylib: terminate called throwing an exception
此错误总是在以下行抛出：
cvMat_test = [image CVMat];
我假设这意味着 Xcode 看不到 CVMat 方法。但是，当我尝试使用 NSImage 实例调用该方法时，Xcode 将该方法列为项目的方法之一。
这是我链接到的另一篇文章中的代码，以防人们不想点击：
//
// NSImage+OpenCV.h
//
#import <AppKit/AppKit.h>
@interface NSImage (NSImage_OpenCV) {
}
+(NSImage*)imageWithCVMat:(const cv::Mat&)cvMat;
-(id)initWithCVMat:(const cv::Mat&)cvMat;
@property(nonatomic, readonly) cv::Mat CVMat;
@property(nonatomic, readonly) cv::Mat CVGrayscaleMat;
@end
实现文件：
//
// NSImage+OpenCV.mm
//
#import "NSImage+OpenCV.h"
static void ProviderReleaseDataNOP(void *info, const void *data, size_t size)
{
return;
}
@implementation NSImage (NSImage_OpenCV)
-(CGImageRef)CGImage
{
CGContextRef bitmapCtx = CGBitmapContextCreate(NULL/*data - pass NULL to let CG allocate the memory*/,
[self size].width,
[self size].height,
8 /*bitsPerComponent*/,
0 /*bytesPerRow - CG will calculate it for you if it's allocating the data. This might get padded out a bit for better alignment*/,
[[NSColorSpace genericRGBColorSpace] CGColorSpace],
kCGBitmapByteOrder32Host|kCGImageAlphaPremultipliedFirst);
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithGraphicsPort:bitmapCtx flipped:NO]];
[self drawInRect:NSMakeRect(0,0, [self size].width, [self size].height) fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];
[NSGraphicsContext restoreGraphicsState];
CGImageRef cgImage = CGBitmapContextCreateImage(bitmapCtx);
CGContextRelease(bitmapCtx);
return cgImage;
}
-(cv::Mat)CVMat
{
CGImageRef imageRef = [self CGImage];
CGColorSpaceRef colorSpace = CGImageGetColorSpace(imageRef);
CGFloat cols = self.size.width;
CGFloat rows = self.size.height;
cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels
CGContextRef contextRef = CGBitmapContextCreate(cvMat.data, // Pointer to backing data
cols, // Width of bitmap
rows, // Height of bitmap
8, // Bits per component
cvMat.step[0], // Bytes per row
colorSpace, // Colorspace
kCGImageAlphaNoneSkipLast |
kCGBitmapByteOrderDefault); // Bitmap info flags
CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), imageRef);
CGContextRelease(contextRef);
CGImageRelease(imageRef);
return cvMat;
}
-(cv::Mat)CVGrayscaleMat
{
CGImageRef imageRef = [self CGImage];
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
CGFloat cols = self.size.width;
CGFloat rows = self.size.height;
cv::Mat cvMat = cv::Mat(rows, cols, CV_8UC1); // 8 bits per component, 1 channel
CGContextRef contextRef = CGBitmapContextCreate(cvMat.data, // Pointer to backing data
cols, // Width of bitmap
rows, // Height of bitmap
8, // Bits per component
cvMat.step[0], // Bytes per row
colorSpace, // Colorspace
kCGImageAlphaNone |
kCGBitmapByteOrderDefault); // Bitmap info flags
CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), imageRef);
CGContextRelease(contextRef);
CGColorSpaceRelease(colorSpace);
CGImageRelease(imageRef);
return cvMat;
}
+ (NSImage *)imageWithCVMat:(const cv::Mat&)cvMat
{
return [[[NSImage alloc] initWithCVMat:cvMat] autorelease];
}
- (id)initWithCVMat:(const cv::Mat&)cvMat
{
NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize() * cvMat.total()];
CGColorSpaceRef colorSpace;
if (cvMat.elemSize() == 1)
{
colorSpace = CGColorSpaceCreateDeviceGray();
}
else
{
colorSpace = CGColorSpaceCreateDeviceRGB();
}
CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
CGImageRef imageRef = CGImageCreate(cvMat.cols, // Width
cvMat.rows, // Height
8, // Bits per component
8 * cvMat.elemSize(), // Bits per pixel
cvMat.step[0], // Bytes per row
colorSpace, // Colorspace
kCGImageAlphaNone | kCGBitmapByteOrderDefault, // Bitmap info flags
provider, // CGDataProviderRef
NULL, // Decode
false, // Should interpolate
kCGRenderingIntentDefault); // Intent
NSBitmapImageRep *bitmapRep = [[NSBitmapImageRep alloc] initWithCGImage:imageRef];
NSImage *image = [[NSImage alloc] init];
[image addRepresentation:bitmapRep];
CGImageRelease(imageRef);
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpace);
return image;
}
@end
我对文件的使用：
#import "AppDelegate.h"
@implementation AppDelegate
- (void)dealloc
{
[super dealloc];
}
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
// Insert code here to initialize your application
cv::Mat cvMat_test;
NSImage *image = [NSImage imageNamed:@"image.jpg"];
cvMat_test = [image CVMat];
}
@end
PS：我尝试将“-all_load”添加到“其他链接器标志”，但这也不起作用。
【问题讨论】：
-
您是否尝试通过静态库添加该类别？如果是这样，请确保 NSImage+OpenCV.mm 文件处于静态库的 Compile Sources 构建阶段。如果您不想将它放在任何类型的库中，请确保 NSImage+OpenCV.mm 文件处于应用程序的编译源构建阶段。
-
@PeterHosey 真是太简单了。所以我的问题不在于 Obj-C 或 Cocoa，而是我对 Xcode 缺乏了解。我刚刚将 NSImage+OpenCV 复制到 Build Phases -> Compile Sources。您能否写下您的评论作为答案，以便我支持并接受它？
标签： objective-c cocoa opencv nsimage mat