寫在前面：二維碼掃描網絡上教程很多，且全面。以后有時間也幫親們封裝一下。
直接上代碼，大家可直接復制到Xcode進行測試。

//
//  QRBuilderTool.h
//  二維碼生成視圖
//
//  Created by zengchunjun on 16/8/23.
//  Copyright ? 2016年 zengchunjun. All rights reserved.
//

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

@interface QRBuilderTool : NSObject
//根據字符串生成一張黑色二維碼
+ (UIImage*)qrCodeImageWithString:(NSString*)str;

// 輸出一張彩色二維碼
+ (UIImage*)imageBlackToTransparent:(UIImage*)image withRed:(CGFloat)red andGreen:(CGFloat)green andBlue:(CGFloat)blue;

// 根據圖片掃描圖中二維碼，返回二維碼中的信息，如圖片中有多個二維碼則返回第一個
+ (NSString *)detectorImage:(UIImage *)image;
@end

//
//  QRBuilderTool.m
//  二維碼生成視圖
//
//  Created by zengchunjun on 16/8/23.
//  Copyright ? 2016年 zengchunjun. All rights reserved.
//

#import "QRBuilderTool.h"


void ProviderReleaseData (void *info, const void *data, size_t size){
    free((void*)data);
}
@implementation QRBuilderTool

+ (UIImage*)qrCodeImageWithString:(NSString*)str{
    if (str && [str isKindOfClass:[NSString class]] && str.length > 0) {
        return [self createNonInterpolatedUIImageFromCIImage:[self createQRForString:str]
                                                   withScale:2*[[UIScreen mainScreen] scale]];
    }
    return nil;
}

+ (CIImage *)createQRForString:(NSString *)qrString
{
    // Need to convert the string to a UTF-8 encoded NSData object
    NSData *stringData = [qrString dataUsingEncoding: NSISOLatin1StringEncoding];
    
    // Create the filter
    CIFilter *qrFilter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    // Set the message content and error-correction level
    [qrFilter setValue:stringData forKey:@"inputMessage"];
    [qrFilter setValue:@"H" forKey:@"inputCorrectionLevel"];
    
    // Send the image back
    return qrFilter.outputImage;
}

+ (UIImage *)createNonInterpolatedUIImageFromCIImage:(CIImage *)image withScale:(CGFloat)scale
{
    // Render the CIImage into a CGImage
    CGImageRef cgImage = [[CIContext contextWithOptions:nil] createCGImage:image fromRect:image.extent];
    // Now we'll rescale using CoreGraphics
    UIGraphicsBeginImageContext(CGSizeMake(image.extent.size.width * scale, image.extent.size.width * scale));
    CGContextRef context = UIGraphicsGetCurrentContext();
    // We don't want to interpolate (since we've got a pixel-correct image)
    CGContextSetInterpolationQuality(context, kCGInterpolationNone);
    CGContextDrawImage(context, CGContextGetClipBoundingBox(context), cgImage);
    // Get the image out
    UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    // Tidy up
    UIGraphicsEndImageContext();
    CGImageRelease(cgImage);
    return scaledImage;
}

// 輸出彩色圖片
+ (UIImage*)imageBlackToTransparent:(UIImage*)image withRed:(CGFloat)red andGreen:(CGFloat)green andBlue:(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);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(rgbImageBuf, imageWidth, imageHeight, 8, bytesPerRow, colorSpace,
                                                 kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
    CGContextDrawImage(context, CGRectMake(0, 0, imageWidth, imageHeight), image.CGImage);
    // 遍歷像素
    int pixelNum = imageWidth * imageHeight;
    uint32_t* pCurPtr = rgbImageBuf;
    for (int i = 0; i < pixelNum; i++, pCurPtr++){
        if ((*pCurPtr & 0xFFFFFF00) < 0x99999900)    // 將白色變成透明
        {
            // 改成下面的代碼，會將圖片轉成想要的顏色
            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;
        }
    }
    // 輸出圖片
    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];
    // 清理空間
    CGImageRelease(imageRef);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    return resultUIImage;
}

+ (NSString *)detectorImage:(UIImage *)image
{
    CIContext *context = [CIContext contextWithOptions:nil];
    // iOS8以后
    CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:context options:@{CIDetectorAccuracy: CIDetectorAccuracyLow}];
    
    NSArray *features = [detector featuresInImage:[CIImage imageWithCGImage:image.CGImage]];
    if (features.count >= 1) {
        CIQRCodeFeature *feature = [features objectAtIndex:0];
        NSString *scannedResult = feature.messageString;
        return scannedResult;
    
    }
    return @"";
}


@end