IOS Creating Color QR Code Example Detailed Explanation

#import "UIImage+" 
 
@implementation UIImage (CreateQRCode) 
 
+ (UIImage *)createQRCode:(NSString *)string andSize:(CGSize)size andColor:(UIColor *)color { 
  UIImage *qrcode = [self createNonInterpolatedUIImageFormCIImage:[self createQRForString:string] withSize:size]; 
  const CGFloat *_components = CGColorGetComponents(); 
  CGFloat red = _components[0] * ; 
  CGFloat green = _components[1] * ; 
  CGFloat blue = _components[2] * ; 
  return [self imageBlackToTransparent:qrcode withRed:red andGreen:green andBlue:blue]; 
} 
 
+ (void)setImageViewShadow:(UIImageView *)view { 
   = CGSizeMake(0, 2); 
   = 2; 
   = [UIColor blackColor].CGColor; 
   = 0.5; 
   = [UIColor clearColor]; 
} 
 
#pragma mark - Create grayscale maps, only grayscale maps can change colors+ (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGSize)size { 
  CGRect extent = CGRectIntegral(); 
  CGFloat scale = MIN(/CGRectGetWidth(extent), /CGRectGetHeight(extent)); 
   
  size_t width = CGRectGetWidth(extent) * scale; 
  size_t height = CGRectGetHeight(extent) * scale; 
   
// iOS does not support device dependency or universal color space.  iOS apps must use device color space// The device color space is mainly used in IOS applications, because other color spaces cannot be used on IOS.  In most cases, Mac OS X applications should use common color space instead of device color space.// CGColorSpaceCreateDeviceGray: Create device dependent grayscale color space// CGColorSpaceCreateDeviceRGB: Create device dependent RGB color space// CGColorSpaceCreateDeviceCMYK: Create device dependent CMYK color space  CGColorSpaceRef cs = CGColorSpaceCreateDeviceGray();//This is the main attribute of changing the color of the QR code. It must be grayscale space. Its function is to transform UIImage into grayscale map   
  CGContextRef bitmapRef = CGBitmapContextCreate(NULL, width, height, 8, 0, cs, kCGImageAlphaNone); 
  CIContext * context = [CIContext contextWithOptions:NULL]; 
  CGImageRef bitmapImage = [context createCGImage:image fromRect:extent]; 
  CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationHigh); 
  CGContextScaleCTM(bitmapRef, scale, scale); 
  CGContextDrawImage(bitmapRef, extent, bitmapImage); 
  CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef); 
   
  CGContextRelease(bitmapRef); 
  CGImageRelease(bitmapImage); 
   
  return [UIImage imageWithCGImage:scaledImage]; 
} 
 
#pragma mark - the main code for creating QR codes+ (CIImage *)createQRForString:(NSString *)qrString { 
  NSData *stringData = [qrString dataUsingEncoding:NSUTF8StringEncoding]; 
  CIFilter *qrFilter = [CIFilter filterWithName:@"CIQRCodeGenerator"]; 
  [qrFilter setValue:stringData forKey:@"inputMessage"]; 
  [qrFilter setValue:@"M" forKey:@"inputCorrectionLevel"]; 
  return ; 
} 
 
#pragma mark - Change the color of the QR codevoid ProviderReleaseData (voidvoid *info, const voidvoid *data, size_t size){ 
  free((void*)data); 
} 
 
+ (UIImage*)imageBlackToTransparent:(UIImage*)image withRed:(CGFloat)red andGreen:(CGFloat)green andBlue:(CGFloat)blue{ 
  const int imageWidth = ; 
  const int imageHeight = ; 
  size_t   bytesPerRow = imageWidth * 4; 
  uint32_t* rgbImageBuf = (uint32_t*)malloc(bytesPerRow * imageHeight); 
   
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
  CGContextRef context = CGBitmapContextCreate(rgbImageBuf, imageWidth, imageHeight, 8, bytesPerRow, colorSpace, 
                         kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast); 
  CGContextDrawImage(context, CGRectMake(0, 0, imageWidth, imageHeight), ); 
   
  int pixelNum = imageWidth * imageHeight; 
  uint32_t* pCurPtr = rgbImageBuf; 
  for (int i = 0; i < pixelNum; i++, pCurPtr++){ 
    if ((*pCurPtr & 0xFFFFFF00) < 0x99999900){ 
      uint8_t* ptr = (uint8_t*)pCurPtr; 
      ptr[3] = red; //0~255 
      ptr[2] = green; 
      ptr[1] = blue; 
    }else{ 
      uint8_t* ptr = (uint8_t*)pCurPtr; 
      ptr[0] = 0; 
    } 
  } 
   
  CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL, rgbImageBuf, bytesPerRow * imageHeight, ProviderReleaseData); 
  CGImageRef imageRef = CGImageCreate(imageWidth, imageHeight, 8, 32, bytesPerRow, colorSpace, 
                    kCGImageAlphaLast | kCGBitmapByteOrder32Little, dataProvider, 
                    NULL, true, kCGRenderingIntentDefault); 
  CGDataProviderRelease(dataProvider); 
  UIImage* resultUIImage = [UIImage imageWithCGImage:imageRef]; 
   
  CGImageRelease(imageRef); 
  CGContextRelease(context); 
  CGColorSpaceRelease(colorSpace); 
   
  return resultUIImage; 
} 
 
@end