iOS颜色摄合器，获取图片某点的颜色值

/**
重设image

@param image image
*/
- (void)setImage:(UIImage *)image {

UIImage *temp = [self imageForResizeWithImage:image resize:CGSizeMake(self.frame.size.width, self.frame.size.width)];
[super setImage:temp];

}

/**
通过上下图文创建self对应像素的image

@param picture 要加载的图片
@param resize 实际self的大小
@return 返回self对应像素的大小的image
*/
- (UIImage *)imageForResizeWithImage:(UIImage *)picture resize:(CGSize)resize {

CGSize imageSize = resize; //CGSizeMake(25, 25)

/**
UIGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque, CGFloat scale);
1.参数size为新创建的位图上下文的大小
2.opaque—透明开关，如果图形完全不用透明，设置为YES以优化位图的存储
3.scale—–缩放因子 iPhone 4是2.0，其他是1.0;实际上设为0后，系统就会自动设置正确的比例了。
*/

UIGraphicsBeginImageContextWithOptions(imageSize, NO,0.0);
CGRect imageRect = CGRectMake(0.0, 0.0, imageSize.width, imageSize.height);
[picture drawInRect:imageRect];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
return image;
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

UITouch *touch = [touches anyObject];

CGPoint location_point = [touch locationInView:self];

if ([YWDistanceTool getlayer:location_point withRadius:self.bounds.size.width/2]) {

UIColor *color = [UIColor colorAtPixel:location_point withImage:self.image];

if (self.pointColorBlock) {
self.pointColorBlock(color);
}
if ([self.delegate respondsToSelector:@selector(getCurrentColor:)]) {
[self.delegate getCurrentColor:color];
}

}

}

- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

UITouch *touch = [touches anyObject];

CGPoint location_point = [touch locationInView:self];

if ([YWDistanceTool getlayer:location_point withRadius:self.bounds.size.width/2]) {

UIColor *color = [UIColor colorAtPixel:location_point withImage:self.image];

if (self.pointColorBlock) {
self.pointColorBlock(color);
}
if ([self.delegate respondsToSelector:@selector(getCurrentColor:)]) {
[self.delegate getCurrentColor:color];
}
}

}

- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {

UITouch *touch = [touches anyObject];
CGPoint location_point = [touch locationInView:self];

if ([YWDistanceTool getlayer:location_point withRadius:self.bounds.size.width/2]) {

UIColor *color = [UIColor colorAtPixel:location_point withImage:self.image];

if (self.pointColorBlock) {
self.pointColorBlock(color);
}
if ([self.delegate respondsToSelector:@selector(getCurrentColor:)]) {
[self.delegate getCurrentColor:color];
}
}

}
/**
获取图片某一点的颜色

@param point 点击图片的某一点
@param image 图片
@return 图片某点的颜色值
*/
+ (UIColor *)colorAtPixel:(CGPoint)point withImage:(UIImage *)image {

//    判断给定的点是否被一个CGRect包含

if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f, image.size.width, image.size.height), point)) {
return nil;
}

//    trunc（n1,n2），n1表示被截断的数字，n2表示要截断到那一位。n2可以是负数，表示截断小数点前。注意，TRUNC截断不是四舍五入。
//    TRUNC(15.79)---15
//    trunc(15.79,1)--15.7

NSInteger pointX = trunc(point.x);

NSInteger pointY = trunc(point.y);

CGImageRef cgImage = image.CGImage;

NSUInteger width = image.size.width;
NSUInteger height = image.size.height;
//    创建色彩标准
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

int bytesPerPixel = 4;

int bytesPerRow = bytesPerPixel * 1;

NSUInteger bitsPerComponent = 8;

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

CGContextRef context = CGBitmapContextCreate(pixelData,
1,
1,
bitsPerComponent,
bytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast |     kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextSetBlendMode(context, kCGBlendModeCopy);

CGContextTranslateCTM(context, -pointX, pointY-(CGFloat)height);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, (CGFloat)width, (CGFloat)height), cgImage);
CGContextRelease(context);

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];

}