如何更改CIFilter CIQRCodeGenerator过滤器的背景和前景颜色

这是一个快速示例（针对Google员工）

func qrCode(from string: String) -> UIImage? {
    let data = string.data(using: .ascii)

    // Generate the code image with CIFilter
    guard let filter = CIFilter(name: "CIQRCodeGenerator") else { return nil }
    filter.setValue(data, forKey: "inputMessage")

    // Scale it up (because it is generated as a tiny image)
    let scale = UIScreen.main.scale
    let transform = CGAffineTransform(scaleX: scale, y: scale)
    guard let output = filter.outputImage?.transformed(by: transform) else { return nil }

    // Change the color using CIFilter
    let colorParameters = [
        "inputColor0": CIColor(color: UIColor.black), // Foreground
        "inputColor1": CIColor(color: UIColor.clear) // Background
    ]
    let colored = output.applyingFilter("CIFalseColor", parameters: colorParameters)

    return UIImage(ciImage: colored)
}

CIQRCodeGenerator 只生成黑白QR码,但您可以轻松地将生成的图像转换为另一种配色方案.

创建CIFalseColor过滤器的实例 ,将其设置inputImage为outputImage您的生成器,以及它inputColor0和inputColor1您要使用的颜色而不是黑色和白色.然后将假色滤镜绘制outputImage到CG上下文中.

您还可以考虑使用CIMaskToAlpha滤镜将QR码图像中的黑色或白色变为透明; 然后你就可以把它放在任何背景颜色之上.(只是不要把它放在太忙的背景上,否则人们将无法扫描它.)

这是现在有效的代码: -

+ (NSImage *)createQRImageForString:(NSString *)string backgroundColor:(CIColor*)iBackgroundColor foregroundColor:(CIColor*)iForegroundColor size:(CGSize)size {

CIImage *image;
CIFilter *filter;
CIFilter *filterColor;

// Setup the QR filter with our string
filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
[filter setDefaults];

NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
[filter setValue:data forKey:@"inputMessage"];
image = [filter valueForKey:@"outputImage"];

filterColor = [CIFilter filterWithName:@"CIFalseColor" keysAndValues:@"inputImage", image, @"inputColor0", iForegroundColor, @"inputColor1", iBackgroundColor, nil];
//[filterColor setDefaults];

image = [filterColor valueForKey:@"outputImage"];


//image = [CIImage imageWithColor:[CIColor colorWithRed:1 green: 0 blue: 0]];

// Calculate the size of the generated image and the scale for the desired image size
CGRect extent = CGRectIntegral(image.extent);
CGFloat scale = MIN(size.width / CGRectGetWidth(extent), size.height / CGRectGetHeight(extent));

// Since CoreImage nicely interpolates, we need to create a bitmap image that we'll draw into
// a bitmap context at the desired size;
size_t width = CGRectGetWidth(extent) * scale;
size_t height = CGRectGetHeight(extent) * scale;
CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 256*4, cs, (CGBitmapInfo)kCGImageAlphaPremultipliedFirst);

#if TARGET_OS_IPHONE
CIContext *context = [CIContext contextWithOptions:nil];
#else
CIContext *context = [CIContext contextWithCGContext:bitmapRef options:nil];
#endif

CGImageRef bitmapImage = [context createCGImage:image fromRect:extent];

CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);
CGContextScaleCTM(bitmapRef, scale, scale);
CGContextDrawImage(bitmapRef, extent, bitmapImage);

// Create an image with the contents of our bitmap
CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);

// Cleanup
CGContextRelease(bitmapRef);
CGImageRelease(bitmapImage);

return [[NSImage alloc] initWithCGImage:scaledImage size:NSZeroSize];
}