用另一种颜色替换图像内的特定颜色

Question

我有一个"房间"的形象.

现在,用户将点击任何特定的颜色,假设图像中有蓝色.

并且用户还将选择替换的颜色,如"黑色"颜色.

因此,图像内的所有"蓝色"颜色将被"黑色"替换.

任何人都知道如何在iPhone中实现这一目标？

感谢帮助.

Answer 1

1. 您必须遍历图像中的每个像素并获取其rgb值
2. 检查其rgb值是否与fromColor rgb值匹配,如果是,则将像素值更改为toColor rgb值.如果不是,请保留该像素并转到下一个像素.

从记忆中写出一个功能......可能的错误......纠正自己

-(UIImage*)changeColor:(UIImage*)myImage fromColor:(UIColor*)fromColor toColor:(UIColor*)toColor{
    CGImageRef originalImage    = [myImage CGImage];
    CGColorSpaceRef colorSpace  = CGColorSpaceCreateDeviceRGB();
    CGContextRef bitmapContext  = 
CGBitmapContextCreate(NULL,CGImageGetWidth(originalImage),CGImageGetHeight(originalImage),
 8,CGImageGetWidth(originalImage)*4,colorSpace,kCGImageAlphaPremultipliedLast);
    CGColorSpaceRelease(colorSpace);
    CGContextDrawImage(bitmapContext, CGRectMake(0, 0, 
CGBitmapContextGetWidth(bitmapContext),CGBitmapContextGetHeight(bitmapContext)), 
originalImage);
    UInt8 *data          = CGBitmapContextGetData(bitmapContext);
    int numComponents    = 4;
    int bytesInContext   = CGBitmapContextGetHeight(bitmapContext) *      
    CGBitmapContextGetBytesPerRow(bitmapContext);
    double redIn, greenIn, blueIn,alphaIn;
    CGFloat fromRed,fromGreen,fromBlue,fromAlpha;
    CGFloat toRed,toGreen,toBlue,toAlpha; 

    //Get RGB values of fromColor
    int fromCountComponents = CGColorGetNumberOfComponents([fromColor CGColor]);
    if (fromCountComponents == 4) {
     const CGFloat *_components = CGColorGetComponents([fromColor CGColor]);
     fromRed = _components[0];
     fromGreen = _components[1];
     fromBlue = _components[2];
     fromAlpha = _components[3];
    }


    //Get RGB values for toColor
    int toCountComponents = CGColorGetNumberOfComponents([toColor CGColor]);
    if (toCountComponents == 4) {
      const CGFloat *_components = CGColorGetComponents([toColor CGColor]);
      toRed   = _components[0];
      toGreen = _components[1];
      toBlue  = _components[2];
      toAlpha = _components[3];
    }


    //Now iterate through each pixel in the image..
    for (int i = 0; i < bytesInContext; i += numComponents) {
        //rgba value of current pixel..
        redIn    =   (double)data[i]/255.0;
        greenIn  =   (double)data[i+1]/255.0;
        blueIn   =   (double)data[i+2]/255.0;
        alphaIn  =   (double)data[i+3]/255.0;

        //now you got current pixel rgb values...check it curresponds with your fromColor
        if( redIn == fromRed && greenIn == fromGreen && blueIn == fromBlue ){
            //image color matches fromColor, then change current pixel color to toColor
            data[i]    =   toRed;
            data[i+1]  =   toGreen;
            data[i+2]  =   toBlue;
            data[i+3]  = toAlpha;       
        }
    }
    CGImageRef outImage =   CGBitmapContextCreateImage(bitmapContext);
    myImage             =   [UIImage imageWithCGImage:outImage];
    CGImageRelease(outImage);
    return myImage;
}

我希望你不是每次都要调用这个函数......它有点处理器重...如果我是你的处理器,我会对你不满意.. :)

Answer 2

我偶然发现这个答案，寻找用另一种颜色替换一种颜色的方法。好吧，因为我需要 Swift 代码，所以我进行了多次尝试，并找到了一个不错的解决方案。感谢@Rob 的回答。

extension UIImageView {

    @discardableResult func replace(color: UIColor, withColor replacingColor: UIColor) -> Bool {
        guard let inputCGImage = self.image?.cgImage else {
            return false
        }
        let colorSpace       = CGColorSpaceCreateDeviceRGB()
        let width            = inputCGImage.width
        let height           = inputCGImage.height
        let bytesPerPixel    = 4
        let bitsPerComponent = 8
        let bytesPerRow      = bytesPerPixel * width
        let bitmapInfo       = RGBA32.bitmapInfo

        guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) else {
            print("unable to create context")
            return false
        }
        context.draw(inputCGImage, in: CGRect(x: 0, y: 0, width: width, height: height))

        guard let buffer = context.data else {
            return false
        }

        let pixelBuffer = buffer.bindMemory(to: RGBA32.self, capacity: width * height)

        let inColor = RGBA32(color: color)
        let outColor = RGBA32(color: replacingColor)
        for row in 0 ..< Int(height) {
            for column in 0 ..< Int(width) {
                let offset = row * width + column
                if pixelBuffer[offset] == inColor {
                    pixelBuffer[offset] = outColor
                }
            }
        }

        guard let outputCGImage = context.makeImage() else {
            return false
        }
        self.image = UIImage(cgImage: outputCGImage, scale: self.image!.scale, orientation: self.image!.imageOrientation)
        return true
    }

}

其中 RGBA32 结构很简单：

struct RGBA32: Equatable {
    private var color: UInt32

    var redComponent: UInt8 {
        return UInt8((self.color >> 24) & 255)
    }

    var greenComponent: UInt8 {
        return UInt8((self.color >> 16) & 255)
    }

    var blueComponent: UInt8 {
        return UInt8((self.color >> 8) & 255)
    }

    var alphaComponent: UInt8 {
        return UInt8((self.color >> 0) & 255)
    }

    init(red: UInt8, green: UInt8, blue: UInt8, alpha: UInt8) {
        self.color = (UInt32(red) << 24) | (UInt32(green) << 16) | (UInt32(blue) << 8) | (UInt32(alpha) << 0)
    }

    init(color: UIColor) {
        let components = color.cgColor.components ?? [0.0, 0.0, 0.0, 1.0]
        let colors = components.map { UInt8($0 * 255) }
        self.init(red: colors[0], green: colors[1], blue: colors[2], alpha: colors[3])
    }

    static let bitmapInfo = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Little.rawValue

    static func ==(lhs: RGBA32, rhs: RGBA32) -> Bool {
        return lhs.color == rhs.color
    }

}

这样，无论在代码中的任何位置：

let imageView = UIImageView()
let image = UIImage(color: .red) // (*)
imageView.image = image
imageView.replace(color: .red, withColor: .green)

(*)此处解释了用颜色创建图像。