Question

我正试图使用专门的CIImage滤镜来获得类似于颜色遮罩的东西。

基本上，我希望让所有黑色像素都透明。我不介意所有非黑色像素最终都具有什么颜色，只要它们具有最大的alpha值。

我在Core Graphics中熟悉的代码就是这样：

// Convert black sections to transparent using a color mask
const CGFloat maskingColors[6] = { 0, 0, 0, 0, 0, 0 };
CGImageRef result = CGImageCreateWithMaskingColors(image, maskingColors);

我使用彩色矩阵滤镜在核心图像中拍摄了一张照片，但它只是将result设置为nil，因为CIVector值大于1.0f。

// Create color matrix filter
CIFilter *matrix = [CIFilter filterWithName:@"CIColorMatrix"];

// Set filter properties
[matrix setValue:image forKey:kCIInputImageKey];
[matrix setValue:[CIVector vectorWithX:1.0f Y:0.0f Z:0.0f W:0.0f] forKey:@"inputRVector"];
[matrix setValue:[CIVector vectorWithX:0.0f Y:1.0f Z:0.0f W:0.0f] forKey:@"inputGVector"];
[matrix setValue:[CIVector vectorWithX:0.0f Y:0.0f Z:1.0f W:0.0f] forKey:@"inputBVector"];
[matrix setValue:[CIVector vectorWithX:255.0f Y:255.0f Z:255.0f W:0.0f] forKey:@"inputAVector"];

// Get the mapped image
CIImage *result = [matrix valueForKey:kCIOutputImageKey];

注意：对于它的价值，这是一个OSX应用程序。

Answer 1

修改

使用（简单）自定义CIFilter的解决方案。此方法仅适用于OSX，因为iOS不支持自定义过滤器：

CIFilter子类（或多或少是Apple's How-To的副本）：

#import <QuartzCore/QuartzCore.h> @interface MaskFilter : CIFilter { CIImage *inputImage; } @end @implementation MaskFilter static CIKernel *maskFilterKernel = nil; + (void)initialize { [CIFilter registerFilterName: @"MaskFilter" constructor: (id)self classAttributes: [NSDictionary dictionaryWithObjectsAndKeys: @"Mask Filter", kCIAttributeFilterDisplayName, [NSArray arrayWithObjects: kCICategoryColorAdjustment, kCICategoryStillImage, kCICategoryInterlaced, kCICategoryNonSquarePixels,nil], kCIAttributeFilterCategories, nil] ]; } + (CIFilter *)filterWithName:(NSString *)name { CIFilter *filter; filter = [[self alloc] init]; return filter; } - (id)init { if(maskFilterKernel == nil) { NSBundle *bundle = [NSBundle bundleForClass:[self class]]; NSString *code = [NSString stringWithContentsOfFile:[bundle pathForResource:@"MaskFilter" ofType: @"cikernel"] encoding:NSUTF8StringEncoding error:nil]; NSArray *kernels = [CIKernel kernelsWithString:code]; maskFilterKernel = [kernels objectAtIndex:0]; } return [super init]; } - (CIImage *)outputImage { CISampler *src = [CISampler samplerWithImage: inputImage]; return [self apply:maskFilterKernel, src, kCIApplyOptionDefinition, [src definition], nil]; } @end

完成所有工作的自定义内核（Filename：MaskFilter.cikernel）

kernel vec4 maskFilterKernel(sampler src) { vec4 t = sample(src, destCoord()); t.w = (t.x == 0.0 ? (t.y == 0.0 ? (t.z == 0.0 ? 0.0 : 1.0) : 1.0) : 1.0); return t; }

使用Filter就像内置过滤器一样：

CIFilter *filter = [MaskFilter filterWithName:@"MaskFilter"]; [filter setValue:ciImage forKey:@"inputImage"]; CIImage *mask = [filter valueForKey: @"outputImage"];

添加参数以选择要用作遮罩颜色的颜色应该没问题。

OLD ANSWER

使用内置的方法和类，我只能提出这个相当不优雅的解决方案（仅使用Core Image过滤器）：

// convert all colors so they are brighter or equal to 0.5, except black CIFilter *binary = [CIFilter filterWithName:@"CIColorMatrix"]; [binary setValue:inputImage forKey:@"inputImage"]; [binary setValue:[CIVector vectorWithX:1 Y:1 Z:1 W:0] forKey:@"inputRVector"]; [binary setValue:[CIVector vectorWithX:1 Y:1 Z:1 W:0] forKey:@"inputGVector"]; [binary setValue:[CIVector vectorWithX:1 Y:1 Z:1 W:0] forKey:@"inputBVector"]; [binary setValue:[CIVector vectorWithX:0.49999 Y:0.49999 Z:0.49999 W:0] forKey:@"inputBiasVector"]; inputImage = [binary valueForKey:@"outputImage"]; // convert to black/white only colors binary = [CIFilter filterWithName:@"CIColorPosterize"]; [binary setDefaults]; [binary setValue:inputImage forKey:@"inputImage"]; [binary setValue:@2 forKey:@"inputLevels"]; inputImage = [binary valueForKey:@"outputImage"]; // get mask CIFilter *mask = [CIFilter filterWithName:@"CIMaskToAlpha"]; [mask setDefaults]; [mask setValue: inputImage forKey:@"inputImage"];

Answer 2

它将黑色转换为透明，并将其他颜色转换为白色

    func filteredImage(cgImage: CGImage) -> UIImage {
        if let matrixFilter = CIFilter(name: "CIColorMatrix") {
            matrixFilter.setDefaults()
            matrixFilter.setValue(CIImage(cgImage: cgImage), forKey: kCIInputImageKey)
            let rgbVector = CIVector(x: 0, y: 0, z: 0, w: 0)
            let aVector = CIVector(x: 1, y: 1, z: 1, w: 0)
            matrixFilter.setValue(rgbVector, forKey: "inputRVector")
            matrixFilter.setValue(rgbVector, forKey: "inputGVector")
            matrixFilter.setValue(rgbVector, forKey: "inputBVector")
            matrixFilter.setValue(aVector, forKey: "inputAVector")
            matrixFilter.setValue(CIVector(x: 1, y: 1, z: 1, w: 0), forKey: "inputBiasVector")

            if let matrixOutput = matrixFilter.outputImage, let cgImage = CIContext().createCGImage(matrixOutput, from: matrixOutput.extent) {
                return UIImage(cgImage: cgImage)
            }

        }
        return self
    }
}

使用CIImage使所有黑色像素透明

2 个答案: