ios – 在Swift中使用CIColorCube过滤器

发布时间：2020-12-14 17:43:27 所属栏目：百科来源：网络整理

导读：我想让CIColorCube过滤器工作.但是,Apple文档仅提供了一个解释不佳的参考示例： // Allocate memoryconst unsigned int size = 64;float *cubeData = (float *)malloc (size * size * size * sizeof (float) * 4);float rgb[3],hsv[3],*c = cubeData;// Popu

我想让CIColorCube过滤器工作.但是,Apple文档仅提供了一个解释不佳的参考示例：

// Allocate memory
const unsigned int size = 64;
float *cubeData = (float *)malloc (size * size * size * sizeof (float) * 4);
float rgb[3],hsv[3],*c = cubeData;

// Populate cube with a simple gradient going from 0 to 1
for (int z = 0; z < size; z++){
    rgb[2] = ((double)z)/(size-1); // Blue value
    for (int y = 0; y < size; y++){
        rgb[1] = ((double)y)/(size-1); // Green value
        for (int x = 0; x < size; x ++){
            rgb[0] = ((double)x)/(size-1); // Red value
            // Convert RGB to HSV
            // You can find publicly available rgbToHSV functions on the Internet
            rgbToHSV(rgb,hsv);
            // Use the hue value to determine which to make transparent
            // The minimum and maximum hue angle depends on
            // the color you want to remove
            float alpha = (hsv[0] > minHueAngle && hsv[0] < maxHueAngle) ? 0.0f: 1.0f;
            // Calculate premultiplied alpha values for the cube
            c[0] = rgb[0] * alpha;
            c[1] = rgb[1] * alpha;
            c[2] = rgb[2] * alpha;
            c[3] = alpha;
            c += 4; // advance our pointer into memory for the next color value
        }
    }
}
// Create memory with the cube data
NSData *data = [NSData dataWithBytesNoCopy:cubeData
                       length:cubeDataSize
                       freeWhenDone:YES];
CIColorCube *colorCube = [CIFilter filterWithName:@"CIColorCube"];
[colorCube setValue:@(size) forKey:@"inputCubeDimension"];
// Set data for cube
[colorCube setValue:data forKey:@"inputCubeData"];

所以我试图用以下内容将其翻译成Swift：

var filter = CIFilter(name: "CIColorCube")
    filter.setValue(ciImage,forKey: kCIInputImageKey)
    filter.setDefaults()

    var size: UInt = 64
    var floatSize = UInt(sizeof(Float))
    var cubeDataSize:size_t = size * size * size * floatSize * 4
    var colorCubeData:Array<Float> = [
    0,1,1
    ]

    var cubeData:NSData = NSData(bytesNoCopy: colorCubeData,length: cubeDataSize)

但是,在尝试创建多维数据集数据时出现错误：

"Extra argument 'bytesNoCopy' in call"

基本上我创建的cubeData错了.你能告诉我如何在Swift中正确创建cubeData对象吗？

谢谢！

解决方法

看起来你是在色度键过滤器配方 described here之后.这里有一些有效的代码.你得到一个透明颜色的过滤器,由它的HSV角度描述：

func RGBtoHSV(r : Float,g : Float,b : Float) -> (h : Float,s : Float,v : Float) {
    var h : CGFloat = 0
    var s : CGFloat = 0
    var v : CGFloat = 0
    let col = UIColor(red: CGFloat(r),green: CGFloat(g),blue: CGFloat(b),alpha: 1.0)
    col.getHue(&h,saturation: &s,brightness: &v,alpha: nil)
    return (Float(h),Float(s),Float(v))
}

func colorCubeFilterForChromaKey(hueAngle: Float) -> CIFilter {

    let hueRange: Float = 60 // degrees size pie shape that we want to replace
    let minHueAngle: Float = (hueAngle - hueRange/2.0) / 360
    let maxHueAngle: Float = (hueAngle + hueRange/2.0) / 360

    let size = 64
    var cubeData = [Float](repeating: 0,count: size * size * size * 4)
    var rgb: [Float] = [0,0]
    var hsv: (h : Float,v : Float)
    var offset = 0

    for z in 0 ..< size {
        rgb[2] = Float(z) / Float(size) // blue value
        for y in 0 ..< size {
            rgb[1] = Float(y) / Float(size) // green value
            for x in 0 ..< size {

                rgb[0] = Float(x) / Float(size) // red value
                hsv = RGBtoHSV(r: rgb[0],g: rgb[1],b: rgb[2])
                // the condition checking hsv.s may need to be removed for your use-case
                let alpha: Float = (hsv.h > minHueAngle && hsv.h < maxHueAngle && hsv.s > 0.5) ? 0 : 1.0 

                cubeData[offset] = rgb[0] * alpha
                cubeData[offset + 1] = rgb[1] * alpha
                cubeData[offset + 2] = rgb[2] * alpha
                cubeData[offset + 3] = alpha
                offset += 4
            }
        }
    }
    let b = cubeData.withUnsafeBufferPointer { Data(buffer: $0) }
    let data = b as NSData

    let colorCube = CIFilter(name: "CIColorCube",withInputParameters: [
        "inputCubeDimension": size,"inputCubeData": data
    ])
    return colorCube!
}

然后进行过滤器调用

让chromaKeyFilter = colorCubeFilterForChromaKey(hueAngle：120)

我使用120作为标准绿屏.

（编辑：李大同）

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