根据背景图片颜色修改文字颜色

- (void)colorAction:(id)sender{
    bgimageV.image = nil;

    UIColor *color = nil;
    int colorNum = arc4random()%2;
    if (colorNum == 0)
        color = [UIColor blackColor];
    else if (colorNum == 1)
        color = [UIColor whiteColor];
    [bgimageV setBackgroundColor:color];

    [self setTextColor];
}


- (void)setTextColor{
    UIColor *color = nil;
    if(bgimageV.image != nil)
        color = [bgimageV.image mostColor];//这里请看这里<a href="\"http://www.cocoachina.com/bbs/read.php?tid=181490\"" target="\"_blank\"" onclick="\"return" checkurl(this)\"="" id="\"url_1\"">http://www.cocoachina.com/bbs/read.php?tid=181490</a>
    else
        color = bgimageV.backgroundColor;
    if([self isLightColor:color])
        [textLabel setTextColor:[UIColor blackColor]];
    else
        [textLabel setTextColor:[UIColor whiteColor]];
}



//判断颜色是不是亮色
-(BOOL) isLightColor:(UIColor*)clr {
    CGFloat components[3];
    [self getRGBComponents:components forColor:clr];
    NSLog(@"%f %f %f", components[0], components[1], components[2]);

    CGFloat num = components[0] + components[1] + components[2];
    if(num < 382)
        return NO;
    else
        return YES;
}



//获取RGB值
- (void)getRGBComponents:(CGFloat [3])components forColor:(UIColor *)color {
#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_6_1
    int bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast;
#else
    int bitmapInfo = kCGImageAlphaPremultipliedLast;
#endif

    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char resultingPixel[4];
    CGContextRef context = CGBitmapContextCreate(&resultingPixel,
                                                 1,
                                                 1,
                                                 8,
                                                 4,
                                                 rgbColorSpace,
                                                 bitmapInfo);
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, CGRectMake(0, 0, 1, 1));
    CGContextRelease(context);
    CGColorSpaceRelease(rgbColorSpace);

    for (int component = 0; component < 3; component++) {
        components[component] = resultingPixel[component];
    }
}

-(UIColor*)mostColor{


#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_6_1
    int bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast;
#else
    int bitmapInfo = kCGImageAlphaPremultipliedLast;
#endif

    //第一步 先把图片缩小 加快计算速度. 但越小结果误差可能越大
    CGSize thumbSize=CGSizeMake(50, 50);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL,
                                                 thumbSize.width,
                                                 thumbSize.height,
                                                 8,//bits per component
                                                 thumbSize.width*4,
                                                 colorSpace,
                                                 bitmapInfo);

    CGRect drawRect = CGRectMake(0, 0, thumbSize.width, thumbSize.height);
    CGContextDrawImage(context, drawRect, self.CGImage);
    CGColorSpaceRelease(colorSpace);



    //第二步 取每个点的像素值
    unsigned char* data = CGBitmapContextGetData (context);

    if (data == NULL) return nil;

    NSCountedSet *cls=[NSCountedSet setWithCapacity:thumbSize.width*thumbSize.height];

    for (int x=0; x<thumbSize.width; x++) {
        for (int y=0; y<thumbSize.height; y++) {

            int offset = 4*(x*y);

            int red = data[offset];
            int green = data[offset+1];
            int blue = data[offset+2];
            int alpha =  data[offset+3];

            NSArray *clr=@[@(red),@(green),@(blue),@(alpha)];
            [cls addObject:clr];

        }
    }
    CGContextRelease(context);


    //第三步 找到出现次数最多的那个颜色
    NSEnumerator *enumerator = [cls objectEnumerator];
    NSArray *curColor = nil;

    NSArray *MaxColor=nil;
    NSUInteger MaxCount=0;

    while ( (curColor = [enumerator nextObject]) != nil )
    {
        NSUInteger tmpCount = [cls countForObject:curColor];

        if ( tmpCount < MaxCount ) continue;

        MaxCount=tmpCount;
        MaxColor=curColor;

    }

    return [UIColor colorWithRed:([MaxColor[0] intValue]/255.0f) green:([MaxColor[1] intValue]/255.0f) blue:([MaxColor[2] intValue]/255.0f) alpha:([MaxColor[3] intValue]/255.0f)];
}