如何在 uiimage 中找到特定颜色并更改该颜色

Question

我想在图像中找到特定的颜色，例如我有一个图像有很多 colours.by 分配红色参数我想改变除红色像素之外的其他颜色像素。请看下图。在上面的更新图像中，只有模糊颜色突出显示所有其他颜色都已更改。

更新图片

Answer 1

好吧，所以我很好奇要实现这个反转有多难 chroma-key，事实证明给定 example from Apple 这很容易！

// Allocate memory
const unsigned int size = 32;
float *cubeData = (float *)malloc (size * size * size * sizeof (float) * 4);
float rgb[3], *c = cubeData;
CGFloat hue = CGFLOAT_MAX;

CGFloat minHueAngle = 210;
CGFloat maxHueAngle = 240;

// 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
            UIColor *color = [UIColor colorWithRed:rgb[0] green:rgb[1] blue:rgb[2] alpha:1];
            [color getHue:&hue saturation:nil brightness:nil alpha:nil];
            hue *= 360;

            // 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 = (hue > minHueAngle && hue < maxHueAngle) ? 1.0f: 0.0f;
            // 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:(size * size * size * sizeof (float) * 4)
                              freeWhenDone:YES];
CIFilter *colorCube = [CIFilter filterWithName:@"CIColorCube"];
[colorCube setValue:@(size) forKey:@"inputCubeDimension"];
[colorCube setValue:data forKey:@"inputCubeData"];

UIImage *originalImage = [UIImage imageNamed:@"yourImageName"];
CIImage *ciImage = [CIImage imageWithCGImage:originalImage.CGImage];
[colorCube setValue:ciImage forKey:kCIInputImageKey];


UIImage *result = [UIImage imageWithCIImage:[colorCube outputImage]];

从您的示例图片中得出这张图片：

我不得不说它看起来相当不错，因为我只修改了一两分钟的值。当然，为了达到你想要的最终结果，你需要使用两个过滤器 - 即 CIPhotoEffectMono 和 CISourceOverCompositing 首先使你的原始图像黑白，然后覆盖 CubeMap 的结果在黑白图像上过滤。

如何在 uiimage 中找到特定颜色并更改该颜色

how to find particular color in an uiimage and change that color

ios

objective-c

core-image