text: #import "GPUImageOutput.h"
  #import "GPUImageFilter.h"
  
  @interface GPUImageFilterGroup : GPUImageOutput <GPUImageInput>
  {
      NSMutableArray *filters;
      BOOL isEndProcessing;
  }
  
  @property(readwrite, nonatomic, strong) GPUImageOutput<GPUImageInput> *terminalFilter;
  @property(readwrite, nonatomic, strong) NSArray *initialFilters;
  @property(readwrite, nonatomic, strong) GPUImageOutput<GPUImageInput> *inputFilterToIgnoreForUpdates; 
  
  // Filter management
  - (void)addFilter:(GPUImageOutput<GPUImageInput> *)newFilter;
  - (void)removeFilter:(GPUImageOutput<GPUImageInput> *)filter;
  - (void)insertFilter:(GPUImageOutput<GPUImageInput> *)newFilter atIndex:(NSUInteger)index;
  - (GPUImageOutput<GPUImageInput> *)filterAtIndex:(NSUInteger)filterIndex;
  - (NSUInteger)filterCount;
  
  @end
  