返回一张图片的主色调

#import <UIKit/UIKit.h>

@interface UIColor (YKD)
/**
 *  返回一张图片的主色调
 */
+ (UIColor *)mostColorWithImage:(UIImage *)image;
@end

//
//  UIColor+YKD.m

#import "UIColor+YKD.h"

@implementation UIColor (YKD)

+ (UIColor *)mostColorWithImage:(UIImage *)image
{
    // 1.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, thumbSize.width*4, colorSpace, kCGImageAlphaPremultipliedLast);
    
    CGRect drawRect = CGRectMake(0, 0, thumbSize.width, thumbSize.height);
    CGContextDrawImage(context, drawRect, image.CGImage);
    CGColorSpaceRelease(colorSpace);
    
    // 2.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);
    
    // 3.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;
    }
    
    // 4.返回
    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