iOS 使用CIFilter生成二维码

iOS7之前，二维码的制作多使用第三方库，比如ZBarSDK等，iOS7之后，可以使用原生的CIFilter生成二维码。

首先需要创建一个imageview来显示二维码：

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

现在开始生成二维码，宽高也可根据自己需要设置：

- (UIImage *)generateQRCode:(NSString *)code width:(CGFloat)width height:(CGFloat)height {

// 生成二维码图片
CIImage *qrcodeImage;
NSData *data = [code dataUsingEncoding:NSISOLatin1StringEncoding allowLossyConversion:false];
CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];

[filter setValue:data forKey:@"inputMessage"]; //设置内容
[filter setValue:@"H" forKey:@"inputCorrectionLevel"]; //设置纠错级别,H为最高
qrcodeImage = [filter outputImage];

// 消除模糊
CGFloat scaleX = width / qrcodeImage.extent.size.width; // extent 返回图片的frame
CGFloat scaleY = height / qrcodeImage.extent.size.height;
CIImage *transformedImage = [qrcodeImage imageByApplyingTransform:CGAffineTransformScale(CGAffineTransformIdentity, scaleX, scaleY)];

return [UIImage imageWithCIImage:transformedImage];
}

这样，一个简单的二维码已经生成，但是生成的二维码只是黑白，在某些时候就需要对生成的二维码进行着色，使用遍历像素的方式改变图片颜色，具体如下：

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);
// 遍历像素
int pixelNum = imageWidth * imageHeight;
uint32_t* pCurPtr = rgbImageBuf;
for (int i = 0; i < pixelNum; i++, pCurPtr++){
if ((*pCurPtr & 0xFFFFFF00) < 0x99999900)    // 将白色变成透明
{
// 改成下面的代码，会将图片转成想要的颜色
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;
}
}
// 输出图片

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];
// 清理空间
CGImageRelease(imageRef);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return resultUIImage;
}

ok，这样生成的二维码就好看多了！