概述
GPUImage是一个著名的图像处理开源库，它让你能够在图片、视频、相机上使用GPU加速的滤镜和其它特效。与CoreImage框架相比，可以根据GPUImage提供的接口，使用自定义的滤镜。项目地址：https://github.com/BradLarson/GPUImage
这篇文章主要是阅读GPUImage框架中的 GPUImageFilterPipeline、GPUImageFilterGroup 这几个类的源码。这两个类都和组合滤镜相关，但是它们又有不同的地方。GPUImageFilterPipeline 继承自NSObject，也没有实现其它协议，而GPUImageFilterGroup继承自GPUImageOutput 实现了GPUImageInput协议。因此，最大的区别就是GPUImageFilterGroup自身可以作为响应链的一员，而GPUImageFilterPipeline则不能。以下是源码内容：
GPUImageFilterPipeline
GPUImageFilterGroup
实现效果
-
从文件中读取滤镜配置。
filterConfig.png -
直接配置滤镜。
filter.png -
自定义组合滤镜。
GPUImageFilterGroup.png
GPUImageFilterPipeline
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 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 )output;
- (id) initWithConfiguration:(NSDictionary*) configuration input:(GPUImageOutput*)input output:(id )output;
- (id) initWithConfigurationFile:(NSURL*) configuration input:(GPUImageOutput*)input output:(id )output;
// 根据输入的filter数组、GPUImageOutput、GPUImageInput构建GPUImageFilterPipeline
- (id)initWithOrderedFilters:(NSArray *)filters input:(GPUImageOutput *)input output:(id )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 )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 )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:®exError];
// 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 *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
Filters
FilterName
GPUImageGammaFilter
Attributes
setGamma:
float(1.0)
FilterName
GPUImageBrightnessFilter
Attributes
setBrightness:
float(0.2)
- 其它方法
// filter的增加、删除、替换
- (void) addFilter:(GPUImageOutput *)filter;
- (void) addFilter:(GPUImageOutput *)filter atIndex:(NSUInteger)insertIndex;
- (void) replaceFilterAtIndex:(NSUInteger)index withFilter:(GPUImageOutput *)filter;
- (void) replaceAllFilters:(NSArray *) newFilters;
- (void) removeFilter:(GPUImageOutput *)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 *)filter atIndex:(NSUInteger)insertIndex {
[self.filters insertObject:filter atIndex:insertIndex];
[self _refreshFilters];
}
// 在末尾增加filter
- (void)addFilter:(GPUImageOutput *)filter {
[self.filters addObject:filter];
[self _refreshFilters];
}
// 替换filter
- (void)replaceFilterAtIndex:(NSUInteger)index withFilter:(GPUImageOutput *)filter {
[self.filters replaceObjectAtIndex:index withObject:filter];
[self _refreshFilters];
}
// 删除filter
- (void) removeFilter:(GPUImageOutput *)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 *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 *)[_filters lastObject] imageFromCurrentFramebuffer];
}
// 根据imageOrientation生成图像
- (UIImage *)currentFilteredFrameWithOrientation:(UIImageOrientation)imageOrientation {
return [(GPUImageOutput *)[_filters lastObject] imageFromCurrentFramebufferWithOrientation:imageOrientation];
}
// 由final filter生成图像
- (CGImageRef)newCGImageFromCurrentFilteredFrame {
return [(GPUImageOutput *)[_filters lastObject] newCGImageFromCurrentlyProcessedOutput];
}
GPUImageFilterGroup
GPUImageFilterGroup继承自GPUImageOutput ，实现了GPUImageInput协议。因此，可以自身可以作为独立的滤镜参与响应链中。相比GPUImageFilterPipeline，GPUImageFilterGroup功能更强大。
- 属性
@property(readwrite, nonatomic, strong) GPUImageOutput *terminalFilter;
@property(readwrite, nonatomic, strong) NSArray *initialFilters;
@property(readwrite, nonatomic, strong) GPUImageOutput *inputFilterToIgnoreForUpdates;
- 方法
// 增加滤镜
- (void)addFilter:(GPUImageOutput *)newFilter;
- (GPUImageOutput *)filterAtIndex:(NSUInteger)filterIndex;
- (NSUInteger)filterCount;
// 增加滤镜
- (void)addFilter:(GPUImageOutput *)newFilter;
{
[filters addObject:newFilter];
}
// 获取滤镜
- (GPUImageOutput *)filterAtIndex:(NSUInteger)filterIndex;
{
return [filters objectAtIndex:filterIndex];
}
// 滤镜数量
- (NSUInteger)filterCount;
{
return [filters count];
}
//
- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
{
for (GPUImageOutput *currentFilter in _initialFilters)
{
if (currentFilter != self.inputFilterToIgnoreForUpdates)
{
[currentFilter newFrameReadyAtTime:frameTime atIndex:textureIndex];
}
}
}
// 设置帧缓存对象
- (void)setInputFramebuffer:(GPUImageFramebuffer *)newInputFramebuffer atIndex:(NSInteger)textureIndex;
{
for (GPUImageOutput *currentFilter in _initialFilters)
{
[currentFilter setInputFramebuffer:newInputFramebuffer atIndex:textureIndex];
}
}
实现过程
- 从文件中读取滤镜配置。
// 加载图片
GPUImagePicture *picture = [[GPUImagePicture alloc] initWithImage:[UIImage imageNamed:@"1.jpg"]];
// 配置文件
NSURL *file = [[NSBundle mainBundle] URLForResource:@"filterConfig" withExtension:@"plist"];
// 滤镜组合
_pipleLine = [[GPUImageFilterPipeline alloc] initWithConfigurationFile:file input:picture output:_imageView];
[picture processImage];
- 直接配置滤镜。
// 加载图片
GPUImagePicture *picture = [[GPUImagePicture alloc] initWithImage:[UIImage imageNamed:@"2.jpg"]];
// filters
GPUImageRGBFilter *rgbFilter = [[GPUImageRGBFilter alloc] init];
GPUImagePerlinNoiseFilter *noiseFilter = [[GPUImagePerlinNoiseFilter alloc] init];
// 配置文件
NSArray *filters = @[rgbFilter, noiseFilter];
// 滤镜组合
_pipleLine = [[GPUImageFilterPipeline alloc] initWithOrderedFilters:filters input:picture output:_imageView];
[picture processImage];
- 自定义组合滤镜。
#import "QMGrayBilateralBlendFilter.h"
NSString *const kGrayBilateralBlendFragmentShaderString = SHADER_STRING
(
varying highp vec2 textureCoordinate;
varying highp vec2 textureCoordinate2;
uniform sampler2D inputImageTexture;
uniform sampler2D inputImageTexture2;
void main()
{
highp vec4 gray = texture2D(inputImageTexture, textureCoordinate);
highp vec4 bilateral = texture2D(inputImageTexture2, textureCoordinate2);
highp float range = distance(textureCoordinate, vec2(0.5, 0.5));
highp vec4 dstClor = bilateral;
if (range < 0.4) {
dstClor = gray;
}
gl_FragColor = dstClor;
//gl_FragColor = vec4(vec3(mix(gray, bilateral, 0.6)), 1.0);
}
);
@implementation QMGrayBilateralBlendFilter
- (instancetype)init
{
if (self = [super init])
{
// GrayscaleFilter
GPUImageGrayscaleFilter *grayFilter = [[GPUImageGrayscaleFilter alloc] init];
[self addFilter:grayFilter];
// BilateralFilter
GPUImageBilateralFilter *bilateralFilter = [[GPUImageBilateralFilter alloc] init];
bilateralFilter.distanceNormalizationFactor = 16.0;
[self addFilter:bilateralFilter];
// GPUImageTwoPassFilter
GPUImageTwoInputFilter *twoPassFilter = [[GPUImageTwoInputFilter alloc] initWithFragmentShaderFromString:kGrayBilateralBlendFragmentShaderString];
// GPUImageHSBFilter
GPUImageHSBFilter *hsbFilter = [[GPUImageHSBFilter alloc] init];
[grayFilter addTarget:twoPassFilter];
[bilateralFilter addTarget:twoPassFilter];
[twoPassFilter addTarget:hsbFilter];
self.initialFilters = @[grayFilter, bilateralFilter];
self.terminalFilter = hsbFilter;
}
return self;
}
@end
总结
GPUImageFilterPipeline、GPUImageFilterGroup 都可用于组合滤镜，GPUImageFilterPipeline相对比较简单，可定制程度较低，而GPUImageFilterGroup则功能比较强大，可定制程度高。在选用的时候可以根据自己的需求，选用不同的滤镜组合。
源码地址：GPUImage源码阅读系列 https://github.com/QinminiOS/GPUImage
系列文章地址：GPUImage源码阅读 http://www.jianshu.com/nb/11749791