ios获得UIImage的主色调方法

网络上有一个算法，但是经过测试误差比较，经过我的完善和修改，误差比较小了，消耗时间差不多，网上的算法的地址：

  http://www.cocoachina.com/bbs/read.php?tid=181490

我自己的修改算法如下：

 

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;
}
@implementation CMUIImageManager
-(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 先把图片缩小 加快计算速度. 但越小结果误差可能越大
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 取每个点的像素值
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)];
//[cls addObject:clr];
}
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)];
}

 

是按照饱和度来计算的，误差要小些

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