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本片介紹關於圖片濾鏡的研究：xoxo_x 著

本文參考：https://github.com/BradLarson/GPUImage#gpuimage

下載地址：
https://github.com/BradLarson/GPUImage/tree/master/examples/IOS/SimpleImageFilter

步驟 內容 第一步 創建預覽View 即必須的GPUImageView 第二步 創建對象 即我們要用到的GPUImagePicture 第三步 創建濾鏡 即這裡我們使用的 GPUImageSobelEdgeDetectionFilter 第四步 設置紋理尺寸 添加濾鏡 addTarget 並開始處理

效果如下：

第一步：

CGRect mainScreenFrame = [[UIScreen mainScreen] applicationFrame];  
GPUImageView *primaryView = [[GPUImageView alloc] initWithFrame:mainScreenFrame];
self.view = primaryView;

第二步：

 UIImage *inputImage = [UIImage imageNamed:@"WID-small.jpg"];
GPUImagePicture *sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage smoothlyScaleOutput:YES];

第三步：

GPUImageOutput<GPUImageInput> *sepiaFilter = [[GPUImageSobelEdgeDetectionFilter alloc] init];

第四步：

//設置紋理尺寸
 [sepiaFilter forceProcessingAtSize:imageView.sizeInPixels];

[sourcePicture addTarget:sepiaFilter];
[sepiaFilter addTarget:imageView];
//開始處理
[sourcePicture processImage];

如果想將圖片保存下來需要使用：

- (void)useNextFrameForImageCapture;
- (UIImage *)imageFromCurrentFramebuffer;

或者使用：

- (UIImage *)imageByFilteringImage:(UIImage *)imageToFilter;

即：

[sepiaFilter useNextFrameForImageCapture];

    UIImage *nearestNeighborImage = [sepiaFilter imageFromCurrentFramebuffer];

或：

UIImage *inputImage = [UIImage imageNamed:@"Lambeau.jpg"];

UIImage *nearestNeighborImage = [sepiaFilter imageByFilteringImage:inputImage];

//文件寫入本地

    NSData *dataForPNGFile1 = UIImagePNGRepresentation(nearestNeighborImage);
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSError *error = nil;

    if (![dataForPNGFile1 writeToFile:[documentsDirectory stringByAppendingPathComponent:@"Lambeau-Resized-fsk.png"] options:NSAtomicWrite error:&error])
    {
        return;
    }

圖片處理分析：

一、分析GPUImageView

@interface GPUImageView : UIView <GPUImageInput>
{
    GPUImageRotationMode inputRotation;
}

繼承：UIView 並遵守GPUImageInput協議

GPUImageInput協議內容如下：

@protocol GPUImageInput <NSObject>
- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
- (void)setInputFramebuffer:(GPUImageFramebuffer *)neWinputFramebuffer atIndex:(NSInteger)textureIndex;
- (NSInteger)nextAvailableTextureIndex;
- (void)setInputSize:(CGSize)newSize atIndex:(NSInteger)textureIndex;
- (void)setInputRotation:(GPUImageRotationMode)neWinputRotation atIndex:(NSInteger)textureIndex;
- (CGSize)maximumOutputSize;
- (void)endProcessing;
- (BOOL)shouldIgnoreUpdatesToThisTarget;
- (BOOL)enabled;
- (BOOL)wantsMonochromeInput;
- (void)

二、分析GPUImagePicture

@interface GPUImagePicture : GPUImageOutput
{
    CGSize pixelSizeOfImage;
    BOOL hasprocessedImage;

    dispatch_semaphore_t imageUpdateSemaphore;
}

// 初始化方法有很多
- (id)initWithURL:(NSURL *)url;
- (id)initWithImage:(UIImage *)newImageSource;
- (id)initWithCGImage:(CGImageRef)newImageSource;
- (id)initWithImage:(UIImage *)newImageSource smoothlyScaleOutput:(BOOL)smoothlyScaleOutput;
- (id)initWithCGImage:(CGImageRef)newImageSource smoothlyScaleOutput:(BOOL)smoothlyScaleOutput;
- (id)initWithImage:(UIImage *)newImageSource removePremultiplication:(BOOL)removePremultiplication;
- (id)initWithCGImage:(CGImageRef)newImageSource removePremultiplication:(BOOL)removePremultiplication;
- (id)initWithImage:(UIImage *)newImageSource smoothlyScaleOutput:(BOOL)smoothlyScaleOutput removePremultiplication:(BOOL)removePremultiplication;
- (id)initWithCGImage:(CGImageRef)newImageSource smoothlyScaleOutput:(BOOL)smoothlyScaleOutput removePremultiplication:(BOOL)removePremultiplication;

// 處理和對輸出圖片大小進行更改
- (void)processImage;
- (CGSize)outputImageSize;

/**
異步處理，回調
 */
- (BOOL)processImageWithCompletionHandler:(void (^)(void))completion;
- (void)processImageUpToFilter:(GPUImageOutput<GPUImageInput> *)finalFilterInChain withCompletionHandler:(void (^)(UIImage *processedImage))block;

三 、分析GPUImageSobelEdgeDetectionFilter （黑白漫畫）

//起名為黑白漫畫 、更好理解些

//所有的濾鏡都是繼承GPUImageFilter

GPUImageSobelEdgeDetectionFilter最終是繼承GPUImageFilter的

@interface GPUImageFilter : GPUImageOutput <GPUImageInput>

所以，我們前面寫到

GPUImageOutput<GPUImageInput> *sepiaFilter = [[GPUImageSobelEdgeDetectionFilter alloc] init];

就是因為繼承的關系。

四、分析addTaget

- (void)addTarget:(id<GPUImageInput>)newTarget;
{
    NSInteger nextAvailableTextureIndex = [newTarget nextAvailableTextureIndex];
    [self addTarget:newTarget atTextureLocation:nextAvailableTextureIndex];

    if ([newTarget shouldIgnoreUpdatesToThisTarget])
    {
        _targetToIgnoreForUpdates = newTarget;
    }
}

我們可以看到addTarget 是GPUImageOutput的方法，也就是說，所有的GPUImageOutput的子類夠可以使用這個函數，即繼承與GPUImageOutput的類，如上面提到的GPUImageFilter。

- (void)addTarget:(id<GPUImageInput>)newTarget;

此外，凡是遵守這個協議的都是newTarget對象，如我們上面提到的GPUImageFilter以及GPUImageView。

本文所涉及到的代碼：

#import <UIKit/UIKit.h>
#import "GPUImage.h"

@interface SimpleImageViewController : UIViewController
{
    GPUImagePicture *sourcePicture;
    GPUImageOutput<GPUImageInput> *sepiaFilter;

}

#import "SimpleImageViewController.h"

@implementation SimpleImageViewController



- (void)viewDidLoad{    
    CGRect mainScreenFrame = [[UIScreen mainScreen] applicationFrame];  
    GPUImageView *primaryView = [[GPUImageView alloc] initWithFrame:mainScreenFrame];
    self.view = primaryView;

    [self setupDisplayFiltering];

}


#pragma mark Image filtering

- (void)setupDisplayFiltering;
{
    UIImage *inputImage = [UIImage imageNamed:@"WID-small.jpg"];

    sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage smoothlyScaleOutput:YES];
    sepiaFilter = [[GPUImageSobelEdgeDetectionFilter alloc] init];

    GPUImageView *imageView = (GPUImageView *)self.view;
    [sepiaFilter forceProcessingAtSize:imageView.sizeInPixels]; 

    [sourcePicture addTarget:sepiaFilter];
    [sepiaFilter addTarget:imageView];

    [sourcePicture processImage];
}

本文用到的圖片：

以上就是iOS GPUImage研究一:圖片濾鏡的全文介紹,希望對您學習和使用ios應用開發有所幫助.

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