二维码图片生成（扩展知识：创建带圆角效果的图片）

效果如下：

ViewController.h

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@property (strong, nonatomic) IBOutlet UIImageView *imgVQRCode;

@end

ViewController.m

#import "ViewController.h"
#import "KMQRCode.h"
#import "UIImage+RoundedRectImage.h"

@interface ViewController ()
- (void)layoutUI;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self layoutUI];
}

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

- (void)layoutUI {
    //用于生成二维码的字符串source
    NSString *source = @"https://github.com/KenmuHuang";
    
    //使用iOS 7后的CIFilter对象操作，生成二维码图片imgQRCode（会拉伸图片，比较模糊，效果不佳）
    CIImage *imgQRCode = [KMQRCode createQRCodeImage:source];
    
    //使用核心绘图框架CG（Core Graphics）对象操作，进一步针对大小生成二维码图片imgAdaptiveQRCode（图片大小适合，清晰，效果好）
    UIImage *imgAdaptiveQRCode = [KMQRCode resizeQRCodeImage:imgQRCode
                                                    withSize:_imgVQRCode.frame.size.width];
    
    //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
    imgAdaptiveQRCode = [KMQRCode specialColorImage:imgAdaptiveQRCode
                                            withRed:33.0
                                              green:114.0
                                               blue:237.0]; //0~255
    
    //使用核心绘图框架CG（Core Graphics）对象操作，创建带圆角效果的图片
    UIImage *imgIcon = [UIImage createRoundedRectImage:[UIImage imageNamed:@"QRCode"]
                                              withSize:CGSizeMake(70.0, 93.0)
                                            withRadius:10];
    //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
    imgAdaptiveQRCode = [KMQRCode addIconToQRCodeImage:imgAdaptiveQRCode
                                              withIcon:imgIcon
                                          withIconSize:imgIcon.size];
    
//    imgAdaptiveQRCode = [KMQRCode addIconToQRCodeImage:imgAdaptiveQRCode
//                                              withIcon:imgIcon
//                                             withScale:3];
    
    _imgVQRCode.image = imgAdaptiveQRCode;
    //设置图片视图的圆角边框效果
    _imgVQRCode.layer.masksToBounds = YES;
    _imgVQRCode.layer.cornerRadius = 10.0;
    _imgVQRCode.layer.borderColor = [UIColor lightGrayColor].CGColor;
    _imgVQRCode.layer.borderWidth = 4.0;
}

@end

​UIImage+RoundedRectImage.h

#import <UIKit/UIKit.h>

@interface UIImage (RoundedRectImage)
+ (UIImage *)createRoundedRectImage:(UIImage *)image withSize:(CGSize)size withRadius:(NSInteger)radius;

@end

UIImage+RoundedRectImage.m

#import "UIImage+RoundedRectImage.h"

@implementation UIImage (RoundedRectImage)

#pragma mark - Private Methods
static void addRoundedRectToPath(CGContextRef contextRef, CGRect rect, float widthOfRadius, float heightOfRadius) {
    float fw, fh;
    if (widthOfRadius == 0 || heightOfRadius == 0)
    {
        CGContextAddRect(contextRef, rect);
        return;
    }
    
    CGContextSaveGState(contextRef);
    CGContextTranslateCTM(contextRef, CGRectGetMinX(rect), CGRectGetMinY(rect));
    CGContextScaleCTM(contextRef, widthOfRadius, heightOfRadius);
    fw = CGRectGetWidth(rect) / widthOfRadius;
    fh = CGRectGetHeight(rect) / heightOfRadius;
    
    CGContextMoveToPoint(contextRef, fw, fh/2);  // Start at lower right corner
    CGContextAddArcToPoint(contextRef, fw, fh, fw/2, fh, 1);  // Top right corner
    CGContextAddArcToPoint(contextRef, 0, fh, 0, fh/2, 1); // Top left corner
    CGContextAddArcToPoint(contextRef, 0, 0, fw/2, 0, 1); // Lower left corner
    CGContextAddArcToPoint(contextRef, fw, 0, fw, fh/2, 1); // Back to lower right
    
    CGContextClosePath(contextRef);
    CGContextRestoreGState(contextRef);
}

#pragma mark - Public Methods
+ (UIImage *)createRoundedRectImage:(UIImage *)image withSize:(CGSize)size withRadius:(NSInteger)radius {
    int w = size.width;
    int h = size.height;
    
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    CGContextRef contextRef = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpaceRef, (CGBitmapInfo)kCGImageAlphaPremultipliedFirst);
    CGRect rect = CGRectMake(0, 0, w, h);
    
    CGContextBeginPath(contextRef);
    addRoundedRectToPath(contextRef, rect, radius, radius);
    CGContextClosePath(contextRef);
    CGContextClip(contextRef);
    CGContextDrawImage(contextRef, CGRectMake(0, 0, w, h), image.CGImage);
    CGImageRef imageMasked = CGBitmapContextCreateImage(contextRef);
    UIImage *img = [UIImage imageWithCGImage:imageMasked];
    
    CGContextRelease(contextRef);
    CGColorSpaceRelease(colorSpaceRef);
    CGImageRelease(imageMasked);
    return img;
}

@end

KMQRCode.h

#import <UIKit/UIKit.h>

@interface KMQRCode : NSObject
+ (CIImage *)createQRCodeImage:(NSString *)source;
+ (UIImage *)resizeQRCodeImage:(CIImage *)image withSize:(CGFloat)size;
+ (UIImage *)specialColorImage:(UIImage*)image withRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue;
+ (UIImage *)addIconToQRCodeImage:(UIImage *)image withIcon:(UIImage *)icon withIconSize:(CGSize)iconSize;
+ (UIImage *)addIconToQRCodeImage:(UIImage *)image withIcon:(UIImage *)icon withScale:(CGFloat)scale;

@end

KMQRCode.m

#import "KMQRCode.h"

@implementation KMQRCode

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

#pragma mark - Public Methods
+ (CIImage *)createQRCodeImage:(NSString *)source {
    NSData *data = [source dataUsingEncoding:NSUTF8StringEncoding];
    
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    [filter setValue:data forKey:@"inputMessage"];
    [filter setValue:@"Q" forKey:@"inputCorrectionLevel"]; //设置纠错等级越高；即识别越容易，值可设置为L(Low) |  M(Medium) | Q | H(High)
    return filter.outputImage;
}

+ (UIImage *)resizeQRCodeImage:(CIImage *)image withSize:(CGFloat)size {
    CGRect extent = CGRectIntegral(image.extent);
    CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
    size_t width = CGRectGetWidth(extent) * scale;
    size_t height = CGRectGetHeight(extent) * scale;
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceGray();
    
    CGContextRef contextRef = CGBitmapContextCreate(nil, width, height, 8, 0, colorSpaceRef, (CGBitmapInfo)kCGImageAlphaNone);
    CIContext *context = [CIContext contextWithOptions:nil];
    CGImageRef imageRef = [context createCGImage:image fromRect:extent];
    CGContextSetInterpolationQuality(contextRef, kCGInterpolationNone);
    CGContextScaleCTM(contextRef, scale, scale);
    CGContextDrawImage(contextRef, extent, imageRef);
    
    CGImageRef imageRefResized = CGBitmapContextCreateImage(contextRef);
    
    //Release
    CGContextRelease(contextRef);
    CGImageRelease(imageRef);
    return [UIImage imageWithCGImage:imageRefResized];
}

+ (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;
}

@end