比较IOS中两个图像的RGB

Question

在我的应用程序中，我需要比较两个图像的RGB是否相同。  我正在使用此代码...

-(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;
} 

但是当我按名称设置图像时，此方法返回相同的RGB值。

Answer 1

"second"