1.?qrStr指的是的是二維碼的字符串，size指的是二維碼的尺寸大小

+ (UIImage *)createQrImage:(NSString *)qrStr withSize:(CGFloat)size{

// 1. 實(shí)例化二維碼濾鏡

CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];

//2// 2. 恢復(fù)濾鏡的默認(rèn)屬性

[filter setDefaults];

// 3. 將字符串轉(zhuǎn)換成NSData

NSData *data = [qrStr dataUsingEncoding:NSUTF8StringEncoding];

// 4.?使用KVC 的方式給filter 賦值

[filter setValue:data forKey:@"inputMessage"];

// 5. 獲得濾鏡輸出的圖像

CIImage *image = [filter outputImage];

//當(dāng)前生成的 二維碼 image 還有很模糊的，所以需要用下面的createNonInterpolatedUIImageFormCIImage方法重繪二維碼

return [self createNonInterpolatedUIImageFormCIImage:image withSize:size];

}

+ (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size {

CGRect extent = CGRectIntegral(image.extent);

CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));

// 1.創(chuàng)建bitmap;

size_t width = CGRectGetWidth(extent) * scale;

size_t height = CGRectGetHeight(extent) * scale;

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到圖片

CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);

CGContextRelease(bitmapRef);

CGImageRelease(bitmapImage);

return [UIImage imageWithCGImage:scaledImage];

}