iPhone:“‘class_name’可能不会响应methd_name”和“unrecognized selector”错误。

我已经编写了一个应用程序,希望在其中将.jpg图像转换为.bmp格式,但它失败,并出现错误:

类“name”可能没有响应 我的名字。

我的代码如下:

#import "CalculateRGBViewController.h"

@implementation CalculateRGBViewController

@synthesize skinImage;
@synthesize lblRedColor,btn,img;
struct pixel {
    unsigned char r, g, b,a;
};


-(IBAction)btnClick:(id) sender{
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    [self presentModalViewController:picker animated:YES];

}
-(void)imagePickerController:(UIImagePickerController *) picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    [picker dismissModalViewControllerAnimated:YES];
    skinImage.  image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];

}

+(void)calculateRGB:(UIImage *)skinImage    {

    struct pixel *pixels = (struct pixel *) calloc(1, skinImage.size.width * skinImage.size.height * sizeof(struct pixel));
    if (pixels != nil)
    {
        // Create a new bitmap

        CGContextRef context = CGBitmapContextCreate(
                                                     (void*) pixels,
                                                     skinImage.size.width,
                                                     skinImage.size.height,
                                                     8,
                                                     skinImage.size.width * 4,
                                                     CGImageGetColorSpace(skinImage.CGImage),
                                                     kCGImageAlphaPremultipliedLast
                                                     );
    NSLog( @"Pixel data one red (%i)", context);        
}

}
-(IBAction)btnCalRGB:(id) sender
{
    [self calculateRGB];

}

The shown me following code. 
-(IBAction)btnCalRGB:(id) sender
{
    [self calculateRGB];


}

警告:Calculatergb控制器可能不会响应btncalrgb按钮功能中的Calculatergb。

编辑01:

我也在代码中实现了,但它再次显示了相同的警告。

[self calculateRGB:anUIImage]; 
-(IBAction)btnCalRGB:(id) sender; 

但它再次显示了同样的警告。当按下上面的按钮时,程序抛出异常。

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[UIImage skinImage]: unrecognized selector sent to