iOS 使用CIFilter生成二維碼

iOS7之前，二維碼的製作多使用第三方庫，比如ZBarSDK等，iOS7之後，可以使用原生的CIFilter生成二維碼。

首先需要創建一個imageview來顯示二維碼：

 _qrCodeSizeImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0,150, 150)];
        _qrCodeSizeImageView.center = CGPointMake(EEOScreenWidth/2, EEOScreenHeight/2);
        _qrCodeSizeImageView.image = [self generateQRCode:@"大帥哥" width:self.qrCodeSizeImageView.frame.size.width height:self.qrCodeSizeImageView.frame.size.height];
        [self.view addSubview:_qrCodeSizeImageView];

現在開始生成二維碼，寬高也可根據自己需要設置：

- (UIImage *)generateQRCode:(NSString *)code width:(CGFloat)width height:(CGFloat)height {
    
    // 生成二維碼圖片
    CIImage *qrcodeImage;
    NSData *data = [code dataUsingEncoding:NSISOLatin1StringEncoding allowLossyConversion:false];
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    
    [filter setValue:data forKey:@"inputMessage"]; //設置內容
    [filter setValue:@"H" forKey:@"inputCorrectionLevel"]; //設置糾錯級別,H爲最高
    qrcodeImage = [filter outputImage];
    
    // 消除模糊
    CGFloat scaleX = width / qrcodeImage.extent.size.width; // extent 返回圖片的frame
    CGFloat scaleY = height / qrcodeImage.extent.size.height;
    CIImage *transformedImage = [qrcodeImage imageByApplyingTransform:CGAffineTransformScale(CGAffineTransformIdentity, scaleX, scaleY)];
    
    return [UIImage imageWithCIImage:transformedImage];
}

這樣，一個簡單的二維碼已經生成，但是生成的二維碼只是黑白，在某些時候就需要對生成的二維碼進行着色，使用遍歷像素的方式改變圖片顏色，具體如下：

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

- (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;
}

ok，這樣生成的二維碼就好看多了！