這次的版本迭代中提一個要獲取主頁圖片的主色調(diào)動態(tài)的去改變子頁面的背景顏色 剛一聽覺得太簡單了 就磨刀霍霍的去開始寫 但是發(fā)現(xiàn)網(wǎng)上很多代碼回去圖片主色調(diào)的方法 都有一個通病就是 獲取圖片主色調(diào) 特別耗時 導(dǎo)致進入子頁面許久才能顯示到背景顏色 查了很多資料 加入了一個算法 大大減少了耗時 也借鑒了其他網(wǎng)友的一些代碼

static void RGBtoHSV( float r, float g, float b, float *h, float *s, float *v )
{
    float min, max, delta;
    min = MIN( r, MIN( g, b ));
    max = MAX( r, MAX( g, b ));
    *v = max;               // v
    delta = max - min;
    if( max != 0 )
        *s = delta / max;       // s
    else {
        // r = g = b = 0        // s = 0, v is undefined
        *s = 0;
        *h = -1;
        return;
    }
    if( r == max )
        *h = ( g - b ) / delta;     // between yellow & magenta
    else if( g == max )
        *h = 2 + ( b - r ) / delta; // between cyan & yellow
    else
        *h = 4 + ( r - g ) / delta; // between magenta & cyan
    *h *= 60;               // degrees
    if( *h < 0 )
        *h += 360;
}


@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // 點擊按鈕更改不同的背景顏色
    for (int i = 0; i<5; i++) {
        UIButton *btn = [UIButton new];
        [btn setBackgroundImage:[UIImage imageNamed:[NSString stringWithFormat:@"%zd",i+1]] forState:UIControlStateNormal];
        
        btn.frame = CGRectMake(200, 100*(i+1), 80, 80);
        [btn addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
        [self.view addSubview:btn];
    }
    
}
- (void)btnClick:(UIButton  *)sender{
    
    UIColor *loginC = [self mostColor:sender.currentBackgroundImage];
    
    self.view.backgroundColor = loginC;

}


-(UIColor*)mostColor:(UIImage*)image{
    
#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_6_1
    int bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast;
#else
    int bitmapInfo = kCGImageAlphaPremultipliedLast;
#endif
    
    //第一步 先把圖片縮小 加快計算速度. 但越小結(jié)果誤差可能越大
    CGSize thumbSize=CGSizeMake(40, 40);
    
    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, image.CGImage);
    CGColorSpaceRelease(colorSpace);
    
    //第二步 取每個點的像素值
    unsigned char* data = CGBitmapContextGetData (context);
    
    if (data == NULL) return nil;
    NSArray *MaxColor=nil;
    // NSCountedSet *cls=[NSCountedSet setWithCapacity:thumbSize.width*thumbSize.height];
    float maxScore=0;
    for (int x=0; x<thumbSize.width*thumbSize.height; x++) {
        
        int offset = 4*x;
        int red = data[offset];
        int green = data[offset+1];
        int blue = data[offset+2];
        int alpha =  data[offset+3];
        
        if (alpha<25)continue;
        
        float h,s,v;
        
        RGBtoHSV(red, green, blue, &h, &s, &v);
        
        float y = MIN(abs(red*2104+green*4130+blue*802+4096+131072)>>13, 235);
        y= (y-16)/(235-16);
        if (y>0.9) continue;
        
        float score = (s+0.1)*x;
        if (score>maxScore) {
            maxScore = score;
        }
        MaxColor=@[@(red),@(green),@(blue),@(alpha)];
        
    }
    
    CGContextRelease(context);
    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)];
}

@end

GitHub https://github.com/liuniuliuniu/LLInterestDemo/tree/master/LLGetPhotoColor
效果圖

獲取圖片主色調(diào).gif