iOS获取图片区域主色的方法

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/**

 *  缩放图片

 *

 *  @param img  image

 *  @param size 缩放后的大小

 *

 *  @return image

 */

+ (UIImage *)scaleToSize:(UIImage *)img size:(CGSize)size{

    // 创建一个bitmap的context

    CGFloat width = CGImageGetWidth(img.CGImage);

    CGFloat height = CGImageGetHeight(img.CGImage);

    CGFloat max = width >= height ? width:height;

    CGSize originSize;

    if (max <= 0) {

        return nil;

    }

    if (width >= height) {

        originSize = CGSizeMake(size.width, (size.width * height)/width);

    }else{

        originSize = CGSizeMake((size.height * width)/height, size.height);

    }

    // 并把它设置成为当前正在使用的context

    UIGraphicsBeginImageContext(size);

    // 绘制改变大小的图片

    [img drawInRect:CGRectMake((size.width - originSize.width)/2, (size.height - originSize.height)/2, originSize.width, originSize.height)];

    // 从当前context中创建一个改变大小后的图片

    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();

    // 使当前的context出堆栈

    UIGraphicsEndImageContext();

    // 返回新的改变大小后的图片

    return scaledImage;

}

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// 裁剪图片

+ (UIImage *)imageFromImage:(UIImage *)image inRect:(CGRect)rect {

    CGImageRef sourceImageRef = [image CGImage];

    CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, rect);

    <360>UIImage *newImage = [UIImage imageWithCGImage:newImageRef];

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/**

 *  获取图片的主色

 *

 *  @param image image

 *  @param scale 精准度0.1~1

 *

 *  @return 图片的主要颜色

 */

+ (NSDictionary *)mostColor:(UIImage *)image scale:(CGFloat)scale{

#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_6_1

    int bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast;

#else

    int bitmapInfo = kCGImageAlphaPremultipliedLast;

#endif

    if (scale <= 0.1) {

        scale = 0.1;

    }else if(scale >= 1){

        scale = 1;

    }

    //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([image size].width * scale, [image size].height * scale);

    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){

        CGContextRelease(context);

        return nil;

    }

    NSCountedSet *cls=[NSCountedSet setWithCapacity:thumbSize.width*thumbSize.height];

  for (int x=0; x<thumbSize.height; x++) {

        for (int y=0; y<thumbSize.width; y++) {

            int offset = 4*(x*thumbSize.width + 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);

    //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;

    }

    //返回三原色色值

    NSMutableDictionary *dic = [[NSMutableDictionary alloc] initWithCapacity:0];

    [dic setValue:@([MaxColor[0] intValue]/255.0f) forKey:@"red"];

    [dic setValue:@([MaxColor[1] intValue]/255.0f) forKey:@"green"];

    [dic setValue:@([MaxColor[2] intValue]/255.0f) forKey:@"blue"];

    return dic;

}

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/**

 *  获取图片上一个点的颜色

 *

 *  @param point 点击的点的位置

 *  @param image image

 *

 *  @return 返回点击点的颜色

 */

+ (UIColor *)colorAtPixel:(CGPoint)point UIImage:(UIImage *)image CGRect:(CGRect)rect{

    // Cancel if point is outside image coordinates

    if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f,rect.size.width, rect.size.height), point)) {

        return nil;

    }

    NSInteger pointX = trunc(point.x);

    NSInteger pointY = trunc(point.y);

    CGImageRef cgImage = image.CGImage;

    NSUInteger width = image.size.width;

    NSUInteger height = image.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    int bytesPerPixel = 4;

    int bytesPerRow = bytesPerPixel * 1;

    NSUInteger bitsPerComponent = 8;

    unsigned char pixelData[4] = { 0, 0, 0, 0 };<1360>

    CGContextRef context = CGBitmapContextCreate(pixelData,

                                                 1,

                                                 1,

                                                 bitsPerComponent,

                                                 bytesPerRow,

                                                 colorSpace,

                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

    CGColorSpaceRelease(colorSpace);

    CGContextSetBlendMode(context, kCGBlendModeCopy);

    // Draw the pixel we are interested in onto the bitmap context

    CGContextTranslateCTM(context, -pointX, pointY-(CGFloat)height);

    CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, (CGFloat)width, (CGFloat)height), cgImage);

    CGContextRelease(context);

    // Convert color values [0..255] to floats [0.0..1.0]

    CGFloat red   = (CGFloat)pixelData[0] / 255.0f;

    CGFloat green = (CGFloat)pixelData[1] / 255.0f;

    CGFloat blue  = (CGFloat)pixelData[2] / 255.0f;

    CGFloat alpha = (CGFloat)pixelData[3] / 255.0f;

    return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];

}