GPUImage源码解读(十八)

GPUImageFilterPipeline 继承自NSObject，它的主要作用是管理滤镜链，自身不能参与响应链中。可以用来构建简单的滤镜组合。如果滤镜比较复杂或是涉及到多个纹理的处理，GPUImageFilterGroup则是更好的选择。

• 属性

// filter数组
@property (strong) NSMutableArray *filters;
// 输入对象
@property (strong) GPUImageOutput *input;
// 输出对象
@property (strong) id <GPUImageInput> output;

• 构造方法。可以通过指定filter数组以及配置字典、文件来构造GPUImageFilterPipeline

- (id) initWithOrderedFilters:(NSArray*) filters input:(GPUImageOutput*)input output:(id <GPUImageInput>)output;
- (id) initWithConfiguration:(NSDictionary*) configuration input:(GPUImageOutput*)input output:(id <GPUImageInput>)output;
- (id) initWithConfigurationFile:(NSURL*) configuration input:(GPUImageOutput*)input output:(id <GPUImageInput>)output;

// 根据输入的filter数组、GPUImageOutput、GPUImageInput构建GPUImageFilterPipeline
- (id)initWithOrderedFilters:(NSArray *)filters input:(GPUImageOutput *)input output:(id <GPUImageInput>)output {
    self = [super init];
    if (self) {
        self.input = input;
        self.output = output;
        self.filters = [NSMutableArray arrayWithArray:filters];
        [self _refreshFilters];
    }
    return self;
}

// 根据filter配置字典、GPUImageOutput、GPUImageInput构建GPUImageFilterPipeline
- (id)initWithConfiguration:(NSDictionary *)configuration input:(GPUImageOutput *)input output:(id <GPUImageInput>)output {
    self = [super init];
    if (self) {
        self.input = input;
        self.output = output;
        if (![self _parseConfiguration:configuration]) {
            NSLog(@"Sorry, a parsing error occurred.");
            abort();
        }
        [self _refreshFilters];
    }
    return self;
}

// 根据filter配置文件的URL、GPUImageOutput、GPUImageInput构建GPUImageFilterPipeline
- (id)initWithConfigurationFile:(NSURL *)configuration input:(GPUImageOutput *)input output:(id <GPUImageInput>)output {
    return [self initWithConfiguration:[NSDictionary dictionaryWithContentsOfURL:configuration] input:input output:output];
}

// 解析配置文件
- (BOOL)_parseConfiguration:(NSDictionary *)configuration {
    NSArray *filters = [configuration objectForKey:@"Filters"];
    if (!filters) {
        return NO;
    }

    NSError *regexError = nil;
    // 匹配配置文件参数如：float(1.0), CGPoint(1.0, 2.0) 等类型
    NSRegularExpression *parsingRegex = [NSRegularExpression regularExpressionWithPattern:@"(float|CGPoint|NSString)\\((.*?)(?:,\\s*(.*?))*\\)"
                                                                                  options:0
                                                                                    error:&regexError];

    // It's faster to put them into an array and then pass it to the filters property than it is to call [self addFilter:] every time
    NSMutableArray *orderedFilters = [NSMutableArray arrayWithCapacity:[filters count]];
    for (NSDictionary *filter in filters) {
        // 由FilterName生成相应的实例对象
        NSString *filterName = [filter objectForKey:@"FilterName"];
        Class theClass = NSClassFromString(filterName);
        GPUImageOutput<GPUImageInput> *genericFilter = [[theClass alloc] init];
        // Set up the properties
        NSDictionary *filterAttributes;
        // 解析Attributes，并传递参数
        if ((filterAttributes = [filter objectForKey:@"Attributes"])) {
            for (NSString *propertyKey in filterAttributes) {
                // Set up the selector
                SEL theSelector = NSSelectorFromString(propertyKey);
                NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[theClass instanceMethodSignatureForSelector:theSelector]];
                [inv setSelector:theSelector];
                [inv setTarget:genericFilter];

                // check selector given with parameter
                if ([propertyKey hasSuffix:@":"]) {

                    stringValue = nil;

                    // Then parse the arguments
                    NSMutableArray *parsedArray;
                    if ([[filterAttributes objectForKey:propertyKey] isKindOfClass:[NSArray class]]) {
                        NSArray *array = [filterAttributes objectForKey:propertyKey];
                        parsedArray = [NSMutableArray arrayWithCapacity:[array count]];
                        for (NSString *string in array) {
                            NSTextCheckingResult *parse = [parsingRegex firstMatchInString:string
                                                                                   options:0
                                                                                     range:NSMakeRange(0, [string length])];

                            NSString *modifier = [string substringWithRange:[parse rangeAtIndex:1]];
                            if ([modifier isEqualToString:@"float"]) {
                                // Float modifier, one argument
                                CGFloat value = [[string substringWithRange:[parse rangeAtIndex:2]] floatValue];
                                [parsedArray addObject:[NSNumber numberWithFloat:value]];
                                [inv setArgument:&value atIndex:2];
                            } else if ([modifier isEqualToString:@"CGPoint"]) {
                                // CGPoint modifier, two float arguments
                                CGFloat x = [[string substringWithRange:[parse rangeAtIndex:2]] floatValue];
                                CGFloat y = [[string substringWithRange:[parse rangeAtIndex:3]] floatValue];
                                CGPoint value = CGPointMake(x, y);
                                [parsedArray addObject:[NSValue valueWithCGPoint:value]];
                            } else if ([modifier isEqualToString:@"NSString"]) {
                                // NSString modifier, one string argument
                                stringValue = [[string substringWithRange:[parse rangeAtIndex:2]] copy];
                                [inv setArgument:&stringValue atIndex:2];

                            } else {
                                return NO;
                            }
                        }
                        [inv setArgument:&parsedArray atIndex:2];
                    } else {
                        NSString *string = [filterAttributes objectForKey:propertyKey];
                        NSTextCheckingResult *parse = [parsingRegex firstMatchInString:string
                                                                               options:0
                                                                                 range:NSMakeRange(0, [string length])];

                        NSString *modifier = [string substringWithRange:[parse rangeAtIndex:1]];
                        if ([modifier isEqualToString:@"float"]) {
                            // Float modifier, one argument
                            CGFloat value = [[string substringWithRange:[parse rangeAtIndex:2]] floatValue];
                            [inv setArgument:&value atIndex:2];
                        } else if ([modifier isEqualToString:@"CGPoint"]) {
                            // CGPoint modifier, two float arguments
                            CGFloat x = [[string substringWithRange:[parse rangeAtIndex:2]] floatValue];
                            CGFloat y = [[string substringWithRange:[parse rangeAtIndex:3]] floatValue];
                            CGPoint value = CGPointMake(x, y);
                            [inv setArgument:&value atIndex:2];
                        } else if ([modifier isEqualToString:@"NSString"]) {
                            // NSString modifier, one string argument
                            stringValue = [[string substringWithRange:[parse rangeAtIndex:2]] copy];
                            [inv setArgument:&stringValue atIndex:2];

                        } else {
                            return NO;
                        }
                    }
                }


                [inv invoke];
            }
        }
        [orderedFilters addObject:genericFilter];
    }
    self.filters = orderedFilters;

    return YES;
}

• 配置文件示例

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Filters</key>
    <array>
        <dict>
            <key>FilterName</key>
            <string>GPUImageGammaFilter</string>
            <key>Attributes</key>
            <dict>
                <key>setGamma:</key>
                <string>float(1.0)</string>
            </dict>
        </dict>
        <dict>
            <key>FilterName</key>
            <string>GPUImageBrightnessFilter</string>
            <key>Attributes</key>
            <dict>
                <key>setBrightness:</key>
                <string>float(0.2)</string>
            </dict>
        </dict>
    </array>
</dict>
</plist>

• 其它方法

// filter的增加、删除、替换
- (void) addFilter:(GPUImageOutput<GPUImageInput> *)filter;
- (void) addFilter:(GPUImageOutput<GPUImageInput> *)filter atIndex:(NSUInteger)insertIndex;
- (void) replaceFilterAtIndex:(NSUInteger)index withFilter:(GPUImageOutput<GPUImageInput> *)filter;
- (void) replaceAllFilters:(NSArray *) newFilters;
- (void) removeFilter:(GPUImageOutput<GPUImageInput> *)filter;
- (void) removeFilterAtIndex:(NSUInteger)index;
- (void) removeAllFilters;

// 由final filter生成图片
- (UIImage *) currentFilteredFrame;
- (UIImage *) currentFilteredFrameWithOrientation:(UIImageOrientation)imageOrientation;
- (CGImageRef) newCGImageFromCurrentFilteredFrame;

// 在特定位置增加filter
- (void)addFilter:(GPUImageOutput<GPUImageInput> *)filter atIndex:(NSUInteger)insertIndex {
    [self.filters insertObject:filter atIndex:insertIndex];
    [self _refreshFilters];
}

// 在末尾增加filter
- (void)addFilter:(GPUImageOutput<GPUImageInput> *)filter {
    [self.filters addObject:filter];
    [self _refreshFilters];
}

// 替换filter
- (void)replaceFilterAtIndex:(NSUInteger)index withFilter:(GPUImageOutput<GPUImageInput> *)filter {
    [self.filters replaceObjectAtIndex:index withObject:filter];
    [self _refreshFilters];
}

// 删除filter
- (void) removeFilter:(GPUImageOutput<GPUImageInput> *)filter;
{
    [self.filters removeObject:filter];
    [self _refreshFilters];
}

// 删除特定索引的filter
- (void)removeFilterAtIndex:(NSUInteger)index {
    [self.filters removeObjectAtIndex:index];
    [self _refreshFilters];
}

// 删除所有filter
- (void)removeAllFilters {
    [self.filters removeAllObjects];
    [self _refreshFilters];
}

// 替换所有filter
- (void)replaceAllFilters:(NSArray *)newFilters {
    self.filters = [NSMutableArray arrayWithArray:newFilters];
    [self _refreshFilters];
}

// 更新响应链
- (void)_refreshFilters {
    // 将input作为响应链源
    id prevFilter = self.input;
    GPUImageOutput<GPUImageInput> *theFilter = nil;

    // 循环添加
    for (int i = 0; i < [self.filters count]; i++) {
        theFilter = [self.filters objectAtIndex:i];
        [prevFilter removeAllTargets];
        [prevFilter addTarget:theFilter];
        prevFilter = theFilter;
    }

    [prevFilter removeAllTargets];

    // 最后将output加入响应链  
    if (self.output != nil) {
        [prevFilter addTarget:self.output];
    }
}

// 由final filter生成图像
- (UIImage *)currentFilteredFrame {
    return [(GPUImageOutput<GPUImageInput> *)[_filters lastObject] imageFromCurrentFramebuffer];
}

// 根据imageOrientation生成图像
- (UIImage *)currentFilteredFrameWithOrientation:(UIImageOrientation)imageOrientation {
  return [(GPUImageOutput<GPUImageInput> *)[_filters lastObject] imageFromCurrentFramebufferWithOrientation:imageOrientation];
}

// 由final filter生成图像
- (CGImageRef)newCGImageFromCurrentFilteredFrame {
    return [(GPUImageOutput<GPUImageInput> *)[_filters lastObject] newCGImageFromCurrentlyProcessedOutput];
}