1.建立一个公用类YDQRCode管理二维码相关的方法

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface YDQRCode : NSObject

2.在.h文件中定义各个方法

=====获取输出的二维码

/**
  *根据链接，获取输出的二维码
 */
+ (CIImage *)createQRForString:(NSString *)qrString ;

=====根据CIImage生成指定大小的UIImage

/**
 根据CIImage生成指定大小的UIImage
 @param image CIImage
 @param size 图片宽度
*/
+(UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size;

=====产生其它颜色的二维码图片

/**
  默认产生的黑白色的二维码图片；我们可以让它产生其它颜色的二维码图片，
  例如：蓝白色的二维码图片
 */
+(UIImage *)specialColorImage:(UIImage*)image withRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue;

=====合并二维码图片和用于中间显示的图标图片

/**
  使用核心绘图框架CG（Core Graphics）对象操作，合并二维码图片和用于中间显示的图标图片
  */
+(UIImage *)addIconToQRCodeImage:(UIImage *)image withIcon:(UIImage *)icon withIconSize:(CGSize)iconSize;

=====合并二维码图片和用于中间显示的图标图片

/**
  使用核心绘图框架CG（Core Graphics）对象操作，
  合并二维码图片和用于中间显示的图标图片
  */
+(UIImage *)addIconToQRCodeImage:(UIImage *)image withIcon:(UIImage *)icon withScale:(CGFloat)scale;

3.在.m文件中实现具体的方法：

#pragma mark - Private Methods
void ProviderReleaseData (void *info, const void *data, size_t size) {
    free((void*)data);
}

#pragma mark - Public Methods
+ (CIImage *) createQRForString:(NSString *)qrString {
    //创建过滤器,使用CIFilter滤镜类生成二维码
    CIFilter * filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    //恢复默认
    [filter setDefaults];
    //给过滤器添加数据（正则表达式/账号和密码）
    NSData * data = [qrString dataUsingEncoding:NSUTF8StringEncoding];
    // 设置内容和纠错级别
    [filter setValue:data forKey:@"inputMessage"];
    [filter setValue:@"M" forKey:@"inputCorrectionLevel"];
    // 返回CIImage
    return filter.outputImage;
}

+ (UIImage *) createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size {
  CGRect extent = CGRectIntegral(image.extent);
  CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
  //1.创建bitmap
  size_t width = CGRectGetWidth(extent) * scale;
  size_t height = CGRectGetHeight(extent) * scale;
  //创建一个DeviceGray颜色空间
  CGColorSpaceRef cs = CGColorSpaceCreateDeviceGray();
  CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, cs, (CGBitmapInfo)kCGImageAlphaNone);  
  CIContext *context = [CIContext contextWithOptions:nil];
  CGImageRef bitmapImage = [context createCGImage:image fromRect:extent];
  CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);
  CGContextScaleCTM(bitmapRef, scale, scale);
  CGContextDrawImage(bitmapRef, extent, bitmapImage);

  // 2.保存bitmap到图片
  CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
  CGContextRelease(bitmapRef);
  CGImageRelease(bitmapImage);

  return [UIImage imageWithCGImage:scaledImage]; 
}


+ (UIImage *) specialColorImage:(UIImage*)image withRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue {
  const int imageWidth = image.size.width;
  const int imageHeight = image.size.height;
  size_t bytesPerRow = imageWidth * 4;
  uint32_t* rgbImageBuf = (uint32_t*)malloc(bytesPerRow * imageHeight);

  //Create context
  CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
  CGContextRef contextRef = CGBitmapContextCreate(rgbImageBuf, imageWidth, imageHeight, 8, bytesPerRow, colorSpaceRef, kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
  CGContextDrawImage(contextRef, CGRectMake(0, 0, imageWidth, imageHeight), image.CGImage);

  //Traverse pixe
  int pixelNum = imageWidth * imageHeight;
  uint32_t* pCurPtr = rgbImageBuf;
  for (int i = 0; i < pixelNum; i++, pCurPtr++) {  
    if ((*pCurPtr & 0xFFFFFF00) < 0x99999900) {
        //Change color
        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;
    }
  }

    //Convert to image
    CGDataProviderRef dataProviderRef = CGDataProviderCreateWithData(NULL, rgbImageBuf, bytesPerRow * imageHeight, ProviderReleaseData);
    CGImageRef imageRef = CGImageCreate(imageWidth, imageHeight, 8, 32, bytesPerRow, colorSpaceRef,
                                    
                                    kCGImageAlphaLast | kCGBitmapByteOrder32Little, dataProviderRef,
                                    NULL, true, kCGRenderingIntentDefault);

    CGDataProviderRelease(dataProviderRef);
    UIImage* img = [UIImage imageWithCGImage:imageRef];
    //Release
    CGImageRelease(imageRef);
    CGContextRelease(contextRef);
    CGColorSpaceRelease(colorSpaceRef);

    return img;

}

+ (UIImage *) addIconToQRCodeImage:(UIImage *)image withIcon:(UIImage *)icon withIconSize:(CGSize)iconSize {
  UIGraphicsBeginImageContext(image.size);
  //通过两张图片进行位置和大小的绘制，实现两张图片的合并；其实此原理做法也可以用于多张图片的合并
  CGFloat widthOfImage = image.size.width;
  CGFloat heightOfImage = image.size.height;
  CGFloat widthOfIcon = iconSize.width;
  CGFloat heightOfIcon = iconSize.height;
  [image drawInRect:CGRectMake(0, 0, widthOfImage, heightOfImage)];
[icon drawInRect:CGRectMake((widthOfImage-widthOfIcon)/2, (heightOfImage-heightOfIcon)/2,
                            widthOfIcon, heightOfIcon)];

  UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  return img;
}

+ (UIImage *) addIconToQRCodeImage:(UIImage *)image withIcon:(UIImage *)icon withScale:(CGFloat)scale {
  UIGraphicsBeginImageContext(image.size);

  //通过两张图片进行位置和大小的绘制，实现两张图片的合并；其实此原理做法也可以用于多张图片的合并
  CGFloat widthOfImage = image.size.width;
  CGFloat heightOfImage = image.size.height;
  CGFloat widthOfIcon = widthOfImage/scale;
  CGFloat heightOfIcon = heightOfImage/scale;

  [image drawInRect:CGRectMake(0, 0, widthOfImage, heightOfImage)];
  [icon drawInRect:CGRectMake((widthOfImage-widthOfIcon)/2, (heightOfImage-heightOfIcon)/2,
                            widthOfIcon, heightOfIcon)];

  UIImage *img = UIGraphicsGetImageFromCurrentImageContext();

  UIGraphicsEndImageContext();

  return img;

 }