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