ios生成高清二维码

开发过程中，可能会用到生成二维码功能，这里不仅生成了二维码，还支持生成指定大小的高清二维码，只需要输入字符串和大小即可生成二维码图片，如下所示

+ (instancetype)generateQrcodeImageWithStr:(NSString *)QcodeStr size:(float)size {
    //属于coreImage，可以查看一下相关文档，有很多效果
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    // 滤镜恢复默认设置
    [filter setDefaults];
    //给滤镜添加数据
    NSData *data = [QcodeStr dataUsingEncoding:NSUTF8StringEncoding];
    [filter setValue:data forKeyPath:@"inputMessage"];
    //返回二维码图片
    return [self createHDUIImageFormCIImage:[filter outputImage] withSize:size];
}

//生成高清图片
+ (UIImage *)createHDUIImageFormCIImage:(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);
    CGColorSpaceRelease(cs);
    CGContextRelease(bitmapRef);
    CGImageRelease(bitmapImage);
    UIImage *newImage = [UIImage imageWithCGImage:scaledImage];
    CGImageRelease(scaledImage);
    return newImage;
}