字符串转清晰二维码

1. qrStr指的是的是二维码的字符串，size指的是二维码的尺寸大小

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

// 1. 实例化二维码滤镜

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

//2// 2. 恢复滤镜的默认属性

[filter setDefaults];

// 3. 将字符串转换成NSData

NSData *data = [qrStr dataUsingEncoding:NSUTF8StringEncoding];

// 4. 使用KVC 的方式给filter 赋值

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

// 5. 获得滤镜输出的图像

CIImage *image = [filter outputImage];

//当前生成的 二维码 image 还有很模糊的，所以需要用下面的createNonInterpolatedUIImageFormCIImage方法重绘二维码

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.创建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到图片

CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);

CGContextRelease(bitmapRef);

CGImageRelease(bitmapImage);

return [UIImage imageWithCGImage:scaledImage];

}