Hãy so sánh RGB của hai hình ảnh trong IOS

Question

Trong ứng dụng của tôi, tôi cần phải so sánh RGB của hai hình ảnh rất giống nhau hay không. Tôi đang sử dụng mã này ...

-(CGFloat)compareImage:(UIImage *)imgPre capturedImage:(UIImage *)imgCaptured 
{  

int colorDiff; 
CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(imgPre.CGImage)); 
int myWidth = (int)CGImageGetWidth(imgPre.CGImage)/2; 
int myHeight =(int)CGImageGetHeight(imgPre.CGImage)/2; 
const UInt8 *pixels = CFDataGetBytePtr(pixelData); 

int bytesPerPixel_ = 4; 
int pixelStartIndex = (myWidth + myHeight) * bytesPerPixel_; 
UInt8 alphaVal = pixels[pixelStartIndex]; 
UInt8 redVal = pixels[pixelStartIndex + 1]; 
UInt8 greenVal = pixels[pixelStartIndex + 2]; 
UInt8 blueVal = pixels[pixelStartIndex + 3]; 
UIColor *color = [UIColor colorWithRed:(redVal/255.0f) green:(greenVal/255.0f) blue:(blueVal/255.0f) alpha:(alphaVal/255.0f)]; 
NSLog(@"color of image=%@",color); 
NSLog(@"color of R=%hhu/G=%hhu/B=%hhu",redVal,greenVal,blueVal); 


CFDataRef pixelDataCaptured = CGDataProviderCopyData(CGImageGetDataProvider(imgCaptured.CGImage)); 
int myWidthCaptured = (int)CGImageGetWidth(imgCaptured.CGImage)/2; 
int myHeightCaptured =(int)CGImageGetHeight(imgCaptured.CGImage)/2; 
const UInt8 *pixelsCaptured = CFDataGetBytePtr(pixelDataCaptured); 

int pixelStartIndexCaptured = (myWidthCaptured + myHeightCaptured) * bytesPerPixel_; 
UInt8 alphaValCaptured = pixelsCaptured[pixelStartIndexCaptured]; 
UInt8 redValCaptured = pixelsCaptured[pixelStartIndexCaptured + 1]; 
UInt8 greenValCaptured = pixelsCaptured[pixelStartIndexCaptured + 2]; 
UInt8 blueValCaptured = pixelsCaptured[pixelStartIndexCaptured + 3]; 
UIColor *colorCaptured = [UIColor colorWithRed:(redValCaptured/255.0f) green:(greenValCaptured/255.0f) blue:(blueValCaptured/255.0f) alpha:(alphaValCaptured/255.0f)]; 
NSLog(@"color of captured image=%@",colorCaptured); 
NSLog(@"color of captured image R=%hhu/G=%hhu/B=%hhu",redValCaptured,greenValCaptured,blueValCaptured); 

colorDiff=sqrt((redVal-249)*(redVal-249)+(greenVal-greenValCaptured)*(greenVal-greenValCaptured)+(blueVal-blueValCaptured)*(blueVal-blueValCaptured)); 

return colorDiff; 
} 

nhưng phương thức này trả về cùng giá trị RGB khi tôi đặt hình ảnh theo tên.

Answer 1

@interface ViewController()<UIImagePickerControllerDelegate, UINavigationControllerDelegate> 
{ 
    IBOutlet UIImageView *imgLeft; 
    IBOutlet UIImageView *imgRight; 

    IBOutlet UILabel *lblLeft; 
    IBOutlet UILabel *lblRight; 

    IBOutlet UILabel *lblResult; 


    CGFloat redLeft,GreenLeft,BlueLeft; 
    CGFloat redRight,GreenRight,BlueRight; 
} 

@end 

@implementation ViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view, typically from a nib. 

    UITapGestureRecognizer * tapRecognizerLeft = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageTappedLeft:)]; 
    [imgLeft addGestureRecognizer:tapRecognizerLeft]; 
    imgLeft.userInteractionEnabled = YES; 

    UITapGestureRecognizer * tapRecognizerRight = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageTappedRight:)]; 
    [imgRight addGestureRecognizer:tapRecognizerRight]; 
    imgRight.userInteractionEnabled = YES; 
} 

- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 

-(IBAction)calculateDistance:(id)sender 
{ 
    CGFloat derivedRedDiff=redLeft-redRight; 
    if (derivedRedDiff<0) { 
     derivedRedDiff*=-1; 
    } 
    CGFloat derivedGreenDiff=GreenLeft-GreenRight; 
    if (derivedGreenDiff<0) { 
     derivedGreenDiff*=-1; 
    } 
    CGFloat derivedBlueDiff=BlueLeft-BlueRight; 
    if (derivedBlueDiff<0) { 
     derivedBlueDiff*=-1; 
    } 

    CGFloat distance=sqrtf(derivedRedDiff*derivedRedDiff+derivedGreenDiff*derivedGreenDiff+derivedBlueDiff*derivedBlueDiff); 
    NSLog(@"Distance = %f",distance); 
    lblResult.text=[NSString stringWithFormat:@"Distance = %f",distance]; 
} 



-(void)imageTappedLeft:(UITapGestureRecognizer *)recognizer 
{ 
    CGPoint point = [recognizer locationInView:imgLeft]; 

    UIGraphicsBeginImageContext(imgLeft.bounds.size); 
    CGContextRef context = UIGraphicsGetCurrentContext(); 
    [imgLeft.layer renderInContext:context]; 

    int bpr =(int) CGBitmapContextGetBytesPerRow(context); 
    unsigned char * data = CGBitmapContextGetData(context); 
    if (data != NULL) 
    { 
     int offset = bpr*round(point.y) + 4*round(point.x); 
     int blue = data[offset+0]; 
     int green = data[offset+1]; 
     int red = data[offset+2]; 
     int alpha = data[offset+3]; 

     CGFloat derivedAlpha=alpha/255.0f; 

     NSLog(@"%d %d %d %d %f", alpha, red, green, blue,derivedAlpha); 

     redLeft=red; 
     GreenLeft=green; 
     BlueLeft=blue; 

     lblLeft.text=[NSString stringWithFormat:@"%d %d %d %f", red, green, blue,derivedAlpha]; 
    } 

    UIGraphicsEndImageContext(); 
} 

-(void)imageTappedRight:(UITapGestureRecognizer *)recognizer 
{ 
    CGPoint point = [recognizer locationInView:imgRight]; 

    UIGraphicsBeginImageContext(imgRight.bounds.size); 
    CGContextRef context = UIGraphicsGetCurrentContext(); 
    [imgRight.layer renderInContext:context]; 

    int bpr =(int) CGBitmapContextGetBytesPerRow(context); 
    unsigned char * data = CGBitmapContextGetData(context); 
    if (data != NULL) 
    { 
     int offset = bpr*round(point.y) + 4*round(point.x); 
     int blue = data[offset+0]; 
     int green = data[offset+1]; 
     int red = data[offset+2]; 
     int alpha = data[offset+3]; 

     CGFloat derivedAlpha=alpha/255.0f; 

     NSLog(@"%d %d %d %d %f", alpha, red, green, blue,derivedAlpha); 

     redRight=red; 
     GreenRight=green; 
     BlueRight=blue; 

     lblRight.text=[NSString stringWithFormat:@"%d %d %d %f", red, green, blue,derivedAlpha]; 
    } 

    UIGraphicsEndImageContext(); 
}