如何获得一个像素的一个UIView的颜色吗？(How to get the color of a p

我想开发一个小应用程序。在这里面，我需要检测的UIView内的像素的颜色。我有一个CGPoint确定我所需要的像素。 UIView的的颜色是使用CoreAnimation改变。

我知道有一些复杂的方式来提取UIImages颜色信息。但是我无法找到UIViews的解决方案。

伪码我在寻找类似

pixel = [view getPixelAtPoint:myPoint];
UIColor *mycolor = [pixel getColor];

任何输入不胜感激。

Answer 1:

这是很可怕的和缓慢的。基本上你创建你分配，以便可以读出存储器中的后备存储器的位图的上下文，则呈现在上下文的观点层和读取在RAM中的相应点。

如果你知道如何做到这一点的图像已经可以做这样的事情：

- (UIImage *)imageForView:(UIView *)view {
  UIGraphicsBeginImageContext(view.frame.size);
  [view.layer renderInContext: UIGraphicsGetCurrentContext()];
  UIImage *retval = UIGraphicsGetImageFromCurrentImageContext(void);
  UIGraphicsEndImageContext();

  return retval;
}

然后你会得到一个图像，你可以得到的像素数据。我相信你有处理图像的机构包括使它们成为背景，所以你可以合并与此，并分解出的实际图像创作。所以，如果你需要，可以和删除，您加载图像和与上下文替换位渲染：

[view.layer renderInContext: UIGraphicsGetCurrentContext()];

你应该是不错的。

Answer 2:

这是更有效的解决方案：

// UIView+ColorOfPoint.h
@interface UIView (ColorOfPoint)
- (UIColor *) colorOfPoint:(CGPoint)point;
@end

// UIView+ColorOfPoint.m
#import "UIView+ColorOfPoint.h"
#import <QuartzCore/QuartzCore.h>

@implementation UIView (ColorOfPoint)

- (UIColor *) colorOfPoint:(CGPoint)point
{
    unsigned char pixel[4] = {0};

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGContextRef context = CGBitmapContextCreate(pixel, 1, 1, 8, 4, colorSpace, kCGBitmapAlphaInfoMask & kCGImageAlphaPremultipliedLast);

    CGContextTranslateCTM(context, -point.x, -point.y);

    [self.layer renderInContext:context];

    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    //NSLog(@"pixel: %d %d %d %d", pixel[0], pixel[1], pixel[2], pixel[3]);

    UIColor *color = [UIColor colorWithRed:pixel[0]/255.0 green:pixel[1]/255.0 blue:pixel[2]/255.0 alpha:pixel[3]/255.0];

    return color;
}

@end

链接到文件： https://github.com/ivanzoid/ikit/tree/master/UIView+ColorOfPoint

Answer 3:

ivanzoid的答案的swift'ified版本

斯威夫特3

extension CALayer {

    func colorOfPoint(point:CGPoint) -> CGColor {

        var pixel: [CUnsignedChar] = [0, 0, 0, 0]

        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)

        let context = CGContext(data: &pixel, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

        context!.translateBy(x: -point.x, y: -point.y)

        self.render(in: context!)

        let red: CGFloat   = CGFloat(pixel[0]) / 255.0
        let green: CGFloat = CGFloat(pixel[1]) / 255.0
        let blue: CGFloat  = CGFloat(pixel[2]) / 255.0
        let alpha: CGFloat = CGFloat(pixel[3]) / 255.0

        let color = UIColor(red:red, green: green, blue:blue, alpha:alpha)

        return color.cgColor
    }
}

斯威夫特2

extension CALayer {

    func colorOfPoint(point:CGPoint)->CGColorRef
    {
        var pixel:[CUnsignedChar] = [0,0,0,0]

        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedLast.rawValue)

        let context = CGBitmapContextCreate(&pixel, 1, 1, 8, 4, colorSpace, bitmapInfo.rawValue)

        CGContextTranslateCTM(context, -point.x, -point.y)

        self.renderInContext(context!)

        let red:CGFloat = CGFloat(pixel[0])/255.0
        let green:CGFloat = CGFloat(pixel[1])/255.0
        let blue:CGFloat = CGFloat(pixel[2])/255.0
        let alpha:CGFloat = CGFloat(pixel[3])/255.0

        let color = UIColor(red:red, green: green, blue:blue, alpha:alpha)

        return color.CGColor
    }

}

基于底层周围CALayer但容易翻译回UIView 。

Answer 4:

修正了一些小错误

- (UIImage *)imageForView:(UIView *)view {
    UIGraphicsBeginImageContext(view.frame.size);
    [view.layer renderInContext: UIGraphicsGetCurrentContext()];
    UIImage *retval = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return retval;
}

此外，添加