iOS 获取图片的主题色（主色调）

-(UIColor *)mainColorOfImage:(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(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, 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;

NSCountedSet cls=[NSCountedSetsetWithCapacity:thumbSize.widththumbSize.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)];

        [clsaddObject: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)];

}

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