Question

我正在尝试在动画期间更改UIImage饱和度。但这样做似乎太沉重/太慢了：

-(void) changeSaturation:(CGFloat)value{

CIContext * context = [CIContext contextWithOptions:nil];

CIFilter *colorControlsFilter = [CIFilter filterWithName:@"CIColorControls"];

 CIImage *image = self.imageView.image.CIImage;

[colorControlsFilter setValue:image forKey:@"inputImage"];

[colorControlsFilter setValue:[NSNumber numberWithFloat:value] forKey:@"inputSaturation"];

CIImage *outputImage = [colorControlsFilter outputImage];

CGImageRef cgimg = [context createCGImage:outputImage
                                 fromRect:[outputImage extent]];

UIImage *newImage = [UIImage imageWithCGImage:cgimg];
self.imageView.image = newImage;

CGImageRelease(cgimg);}

每次用户拖动视图时都会调用此方法（当距离发生变化时，饱和度也会发生变化），这显然不是正确的方法，但我希望有类似的行为。我想知道我是否可以通过UIImageview上的图层来实现这一目标。

有人可以告诉我如何实现我的目标吗？

Answer 1

1）以异步方式计算过滤后的图像：

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{

        UIImage * filtredImage = /*Your method*/

        dispatch_async(dispatch_get_main_queue(), ^{
             self.imageView.image = filtredImage;
        }
}

2）平滑变化图像：使用coreAnimation。 self.layer - 在您的视图中是顶级CALayer

- (UIImage*)changeSaturation:(CGFloat)value
{
     //Your filter process
}
- (void)changeSaturation:(CGFloat)value duration:(CGFloat)duration
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{

            NSUInteger cadreCount = ceil(duration * 60);
            CGFloat incrimentValue = value / cadreCount;

            NSMutableArray * mutArrayAnimationValues = [NSMutableArray new];

            for (int cadreIndex = 0; cadreIndex <= cadreCount; cadreIndex++)
            {
                  CGFloat currentValue = incrimentValue * cadreIndex;
                  UIImage * imageForCurrentCadr = [self changeSaturation:currentValue];
                  [mutArrayAnimationValues addObject:(id)imageForCurrentCadr.CGImage];
            }

            dispatch_async(dispatch_get_main_queue(), ^{

                 self.layer.contents = (id)[mutArrayAnimationValues lastObject];

                 CAKeyframeAnimation *animation = [CAKeyframeAnimation               animationWithKeyPath:@"contents"];
                 [animation setValues:mutArrayAnimationValues];
                 [animation setDuration:duration];
                 [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut]];
                 [animation setFillMode:kCAFillModeBoth];
                 [pathAnimation setRemovedOnCompletion:NO];
                 [self.layer addAnimation:pathAnimation forKey:@"imageAnimation"];
            }
    }
}

Answer 2

原来我的主要问题是被拖动的视图包含一个大分辨率的图像。我的解决方案完全正常。

Answer 3

如果您在0.0和1.0之间更改饱和度，则可以在正常图像上方添加黑白（灰度）图像并更改其alpha值。它将是最高效的。

改变uiimage饱和度的最佳方式（动画期间）

3 个答案: