Filter4Cam 實作: 3. 新增描繪相關方法

since: 2012/02/27
update: 2012/02/28
reference: I touchs: Filter4Cam 學習之 Getting Raw Video Data

A. 開啓 ViewController.h 檔案, 修改如下:
#import <UIKit/UIKit.h>
#import <GLKit/GLKit.h>

//@add
#import <AVFoundation/AVFoundation.h>
#import <CoreMedia/CoreMedia.h>
#import <CoreVideo/CoreVideo.h>
#import <QuartzCore/QuartzCore.h>
#import <CoreImage/CoreImage.h>
#import <ImageIO/ImageIO.h>

//@add
#import "Filter4CamHelper.h"

@interface ViewController : GLKViewController
{
    //@add
    // CIContext: Provides an evaluation context for rendering a CIImage object
    //                      through Quartz 2D or OpenGL.
    CIContext *coreImageContext;
   
    // EAGLContext: Manages the state information, commands, and resources
    //                             needed to draw using OpenGL ES.
    EAGLContext *glContext;
   
    // GLuint: 無符號四位元組整數型態，包含數值從 0 到 4,294,967,295
    GLuint _renderBuffer;
   
    // GLKView: Simplifies the effort required to create an OpenGL ES application
    //                     by providing a default implementation of an OpenGL ES-aware view
    GLKView *glView;
}

//@add
@property (strong, nonatomic) EAGLContext *glContext;
@property (strong, nonatomic) CIContext *coreImageContext;
@property (strong, nonatomic) GLKView *glView;

//@add for Render
- (void)establishRender; // establish Render

@end

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B. 開啓 ViewController.m 檔案, 修改如下:
#import "ViewController.h"

@implementation ViewController

//@add
@synthesize glContext = _glContext;
@synthesize coreImageContext = _coreImageContext;
@synthesize glView = _glView;
....
#pragma mark Getter

//@add: initialize glContext
- (EAGLContext *)glContext
{
    if (_glContext == nil) {
        _glContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    }
   
    return _glContext;
}

//@add: initialize coreImageContext
- (CIContext *)coreImageContext
{
    if (_coreImageContext == nil) {
        _coreImageContext = [CIContext contextWithEAGLContext:self.glContext];
    }
   
    return _coreImageContext;
}

#pragma mark Render

//@add: establish Render
- (void)establishRender
{
    // create EAGLContext: It will auto invoked by glContext "getter".
   
    // setup: glView
    self.glView = (GLKView *)self.view;
    self.glView.context = self.glContext; // call glContext "getter" here.
    self.glView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
   
    // setup: render buffer
    glGenRenderbuffers(1, &_renderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, _renderBuffer);
   
    // init Core Image context: It will auto invoked by coreImageContext "getter".
    // In fact, It will invoked inner
    // captureOutput:didOutputSampleBuffer:fromConnection: method.
}

- (void)viewDidUnload
{   
    [super viewDidUnload];
   
    //@add
    if ([EAGLContext currentContext] == self.glContext) {
        [EAGLContext setCurrentContext:nil];
    }
    self.glContext = nil;
}