使用GPUImage Framework在过滤器链之间切换

Question

我想在两个过滤器链之间切换,如案例1和案例2所示,代码如下.当我最初选择两种情况时,输出显示正确.但是,当我切换到另一个过滤器链时,输出在当前和先前过滤器链之间闪烁.切换过滤链的推荐方法是什么？

-(void) updateFilter:(NSInteger) style {
switch (style) {
    case 1:
        [kuwahara setRadius:5];
        [videoCamera addTarget:kuwahara];
        [kuwahara addTarget:grayscale];
        [grayscale addTarget:filteredVideoView];
        break;
    case 2:    
        [videoCamera addTarget:grayscale];
        [blur setBlurSize:3];
        [grayscale addTarget:blur];
        [blur addTarget:colorinvert];
        [colorinvert addTarget:filteredVideoView];
        break;
    default:
        [videoCamera addTarget:filteredVideoView];
        break;
}
[videoCamera startCameraCapture];
}  

Answer 1

根据应用程序的具体情况,您可能还需要考虑GPUImageFilterPipeline类.

它将负责添加和删除Brad引用的所有干预目标.

如果这些过滤器的重复设置/拆卸对你来说是有问题的,但是在你的班级生活中将它们保存在内存中则不然,那么你可能会欣赏一个管道.

大致基于您提供的内容,它可能看起来像这样:

- (void)configureSomeArraysOfFilters {
    _setNumberOne = [[NSMutableArray alloc] init]; //make sure these arrays are at least scoped to the class, if not actual @properties
    GPUImageKuwaharaFilter* kuwahara = [[GPUImageKuwaharaFilter alloc] init];
    [kuwahara setRadius:5];
    GPUImageGrayscaleFilter* gray = [[GPUImageGrayscaleFilter alloc] init];
    [_setNumberOne addObject:kuwahara];
    [_setNumberOne addObject:gray];


    _setNumberTwo = [[NSMutableArray alloc] init];
    GPUImageGrayscaleFilter* otherGray = [[GPUImageGrayscaleFilter alloc] init];
    GPUImageGaussianBlurFilter* blur = [[GPUImageGaussianBlurFilter alloc] init];
    [blur setBlurSize:3];
    GPUImageColorInvertFilter* invert = [[GPUImageColorInvertFilter alloc] init];
    [_setNumberTwo addObject:otherGray];
    [_setNumberTwo addObject:blur];
    [_setNumberTwo addObject:invert];
}

- (void)configureAnEmptyPipeline {
    if (_samplePipeline == nil) {
        GPUImageFilter* passthrough = [[GPUImageFilter alloc] init];
        NSArray* empty = [NSArray arrayWithObjects:passthrough, nil];
        _samplePipeline = [[GPUImageFilterPipeline alloc] initWithOrderedFilters:empty input:videoCamera output:_filteredVideoView];
        [videoCamera startCameraCapture];
    }
}

- (void)updateFilterPipeline:(NSInteger)style {
    switch (style) {
        case 1:
            [_samplePipeline replaceAllFilters:_setNumberOne];
            break;

        case 2:
            [_samplePipeline replaceAllFilters:_setNumberTwo];

        //add as many more cases as you have defined Arrays full of filters for

        default:
            break;
    }
}

然而,我最喜欢的管道用例是当我在运行时动态创建过滤器集合,然后将它们切换为行动时.它允许我按顺序存储过滤器,然后将它们传递给管道,而不必每次都指定每个过滤器之间的所有目标.

它并不适用于所有情况,但GPUImageFilterPipeline在某些情况下非常有用.