Android 相机库CameraView源码解析 (四) : 带滤镜预览

太过爱你忘了你带给我的痛 2024-04-25 20:24 7阅读 0赞

### 1. 前言 ###

这段时间，在使用 [natario1/CameraView][natario1_CameraView] 来实现带滤镜的`预览`、`拍照`、`录像`功能。  
由于`CameraView`封装的比较到位，在项目前期，的确为我们节省了不少时间。  
但随着项目持续深入，对于`CameraView`的使用进入深水区，逐渐出现满足不了我们需求的情况。  
`Github`中的`issues`中，有些`BUG`作者一直没有修复。

那要怎么办呢 ? 项目迫切地需要实现相关功能，只能自己硬着头皮去看它的源码，去解决这些问题。  
[上篇文章][Link 1]，我们对带滤镜拍照的相关类有了大致的了解，这篇文章我们来看下`CameraView`是怎么实现带滤镜预览的。

以下源码解析基于`CameraView 2.7.2`

implementation("com.otaliastudios:cameraview:2.7.2")

> 为了在博客上更好的展示，本文贴出的代码进行了部分精简

![在这里插入图片描述][c92f5c122cb6428ba2fa01c2f4421049.png]

### 2. 初始化CameraEngine ###

这部分逻辑和普通的预览一样 : [Android 相机库CameraView源码解析 (一) : 预览][Android _CameraView_ _ _] ，这里就略过了。

protected CameraEngine instantiateCameraEngine(Engine engine, CameraEngine.Callback callback) {
        
        if (mExperimental && engine == Engine.CAMERA2) {
        
            return new Camera2Engine(callback);
        } else {
        
            mEngine = Engine.CAMERA1;
            return new Camera1Engine(callback);
        }
    }

### 3. 初始化CameraPreview ###

这里和不同预览不同的地方，是普通的预览创建的是`SurfaceCameraPreview`，而使用`OpenGL`的预览使用的是`GlCameraPreview`

protected CameraPreview instantiatePreview(@NonNull Preview preview,
                                               @NonNull Context context,
                                               @NonNull ViewGroup container) {
        
        switch (preview) {
        
            case SURFACE:
                return new SurfaceCameraPreview(context, container);
            case TEXTURE: {
        
                if (isHardwareAccelerated()) {
        
                    // TextureView is not supported without hardware acceleration.
                    return new TextureCameraPreview(context, container);
                }
            }
            case GL_SURFACE:
            default: {
        
                mPreview = Preview.GL_SURFACE;
                return new GlCameraPreview(context, container);
            }
        }
    }

### 4. 初始化GLSurfaceView ###

在`GlCameraPreview`的`onCreateView()`方法中，初始化了`GLSurfaceView`

#### 4.1 初始化布局 ####

在初始化布局中，通过`findViewById`获得了`GLSurfaceView`

protected GLSurfaceView onCreateView(@NonNull Context context, @NonNull ViewGroup parent) {
        
        ViewGroup root = (ViewGroup) LayoutInflater.from(context)
                .inflate(R.layout.cameraview_gl_view, parent, false);
        final GLSurfaceView glView = root.findViewById(R.id.gl_surface_view);
        
        //...省略了代码...在下文中详细说明
        
    	parent.addView(root, 0);
        mRootView = root;
        return glView;
    }

#### 4.2 初始化Renderer ####

这里创建了`Renderer`类，`Renderer`是我们这里的关键，下文会详细再讲

final Renderer renderer = instantiateRenderer();

protected Renderer instantiateRenderer() {
        
        return new Renderer();
    }

#### 4.3 将GlCameraPreview和Renderer建立关联 ####

这里调用了`glView.setRenderer`，将`GlCameraPreview`和`Renderer`建立了关联

glView.setEGLContextClientVersion(2);
    glView.setRenderer(renderer);
    glView.setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);

### 5. Renderer类 ###

`Renderer`类继承自`GLSurfaceView.Renderer`，有`3`个实现方法`onSurfaceCreated`、`onSurfaceChanged`、`onDrawFrame`

public interface Renderer {
        
        
        void onSurfaceCreated(GL10 gl, EGLConfig config);
    
        void onSurfaceChanged(GL10 gl, int width, int height);
    
        void onDrawFrame(GL10 gl);
    }

#### 5.1 onSurfaceCreated ####

在`onSurfaceCreated`里，我们会初始化`GlTextureDrawer`，并将`Filter`赋值给`GlTextureDrawer`，`GlTextureDrawer`是负责绘制的类。  
接着，由于我们使用的是`GLSurfaceView.RENDERMODE_WHEN_DIRTY`，所以要在合适的时机去调用`requestRender`来通知`OpenGL`渲染。

public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        
        if (mCurrentFilter == null) {
        
            mCurrentFilter = new NoFilter();
        }
        mOutputTextureDrawer = new GlTextureDrawer();
        mOutputTextureDrawer.setFilter(mCurrentFilter);
        final int textureId = mOutputTextureDrawer.getTexture().getId();
        mInputSurfaceTexture = new SurfaceTexture(textureId);
        getView().queueEvent(new Runnable() {
        
            @Override
            public void run() {
        
                for (RendererFrameCallback callback : mRendererFrameCallbacks) {
        
                    callback.onRendererTextureCreated(textureId);
                }
            }
        });
    
        // Since we are using GLSurfaceView.RENDERMODE_WHEN_DIRTY, we must notify
        // the SurfaceView of dirtyness, so that it draws again. This is how it's done.
        mInputSurfaceTexture.setOnFrameAvailableListener(new SurfaceTexture.OnFrameAvailableListener() {
        
            @Override
            public void onFrameAvailable(SurfaceTexture surfaceTexture) {
        
                getView().requestRender(); // requestRender is thread-safe.
            }
        });
    }

还有一点，会分发`RendererFrameCallback`回调的`onRendererTextureCreated()`，带滤镜拍照、录像都实现了`RendererFrameCallback`回调，从而来现实拍照和录像的功能。

*  `SnapshotGlPictureRecorder`中`take()`的时候会添加该回调 : 是用来拍照的。
 *  `SnapshotVideoRecorder` : 是用来录制视频的。

这两个我们后面的文章会讲，这里先略过。

#### 5.2 onSurfaceChanged ####

##### 5.2.1 设置尺寸 #####

在`onSurfaceChanged`方法中，会调用`gl.glViewport`，从而确定`OpenGL`窗口中显示的区域。  
然后会调用`Filter.setSize()`，从而设置滤镜的尺寸。

public void onSurfaceChanged(GL10 gl, final int width, final int height) {
        
        gl.glViewport(0, 0, width, height);
        mCurrentFilter.setSize(width, height);
        if (!mDispatched) {
        
            dispatchOnSurfaceAvailable(width, height);
            mDispatched = true;
        } else if (width != mOutputSurfaceWidth || height != mOutputSurfaceHeight) {
        
            dispatchOnSurfaceSizeChanged(width, height);
        }
    }

##### 5.2.2 裁剪缩放计算 #####

在`dispatchOnSurfaceAvailable()`中，会将宽高赋值给`mOutputSurfaceWidth`和`mOutputSurfaceHeight`

protected final void dispatchOnSurfaceAvailable(int width, int height) {
        
        mOutputSurfaceWidth = width;
        mOutputSurfaceHeight = height;
        if (mOutputSurfaceWidth > 0 && mOutputSurfaceHeight > 0) {
        
            crop(mCropCallback);
        }
        if (mSurfaceCallback != null) {
        
            mSurfaceCallback.onSurfaceAvailable();
        }
    }

并调用`crop`进行裁剪缩放的计算，这里的`mCropping`、`mCropScaleX`、`mCropScaleY` 都会在后面绘制的时候用到。

protected void crop(@Nullable final CropCallback callback) {
        
        if (mInputStreamWidth > 0 && mInputStreamHeight > 0 && mOutputSurfaceWidth > 0
                && mOutputSurfaceHeight > 0) {
        
            float scaleX = 1f, scaleY = 1f;
            AspectRatio current = AspectRatio.of(mOutputSurfaceWidth, mOutputSurfaceHeight);
            AspectRatio target = AspectRatio.of(mInputStreamWidth, mInputStreamHeight);
            if (current.toFloat() >= target.toFloat()) {
        
                // We are too short. Must increase height.
                scaleY = current.toFloat() / target.toFloat();
            } else {
        
                // We must increase width.
                scaleX = target.toFloat() / current.toFloat();
            }
            mCropping = scaleX > 1.02f || scaleY > 1.02f;
            mCropScaleX = 1F / scaleX;
            mCropScaleY = 1F / scaleY;
            getView().requestRender();
        }
        if (callback != null) callback.onCrop();
    }

#### 5.3 onDrawFrame ####

在我们调用`requestRender()`后，就会触发`onDrawFrame`。  
在`onDrawFrame`中，会操作`OpenGL`进行重新的绘制，并渲染到`GlSurfaceView`上，从而达到预览的效果。

##### 5.3.1 进行裁剪、旋转等操作 #####

这部分获取了`transform`矩阵，然后根据之前计算出来的`mCropping`、`mCropScaleX`、`mCropScaleY` 等参数进行裁剪和旋转的操作

final float[] transform = mOutputTextureDrawer.getTextureTransform();
    mInputSurfaceTexture.updateTexImage();
    mInputSurfaceTexture.getTransformMatrix(transform);
    // LOG.v("onDrawFrame:", "timestamp:", mInputSurfaceTexture.getTimestamp());
    
    // For Camera2, apply the draw rotation.
    // See TextureCameraPreview.setDrawRotation() for info.
    if (mDrawRotation != 0) {
        
        Matrix.translateM(transform, 0, 0.5F, 0.5F, 0);
        Matrix.rotateM(transform, 0, mDrawRotation, 0, 0, 1);
        Matrix.translateM(transform, 0, -0.5F, -0.5F, 0);
    }
    
    if (isCropping()) {
        
        // Scaling is easy, but we must also translate before:
        // If the view is 10x1000 (very tall), it will show only the left strip
        // of the preview (not the center one).
        // If the view is 1000x10 (very large), it will show only the bottom strip
        // of the preview (not the center one).
        float translX = (1F - mCropScaleX) / 2F;
        float translY = (1F - mCropScaleY) / 2F;
        Matrix.translateM(transform, 0, translX, translY, 0);
        Matrix.scaleM(transform, 0, mCropScaleX, mCropScaleY, 1);
    }

##### 5.3.2 进行绘制 #####

接着，调用`mOutputTextureDrawer.draw()`从而重新进行绘制，并渲染到`GlSurfaceView`上，从而达到了预览的效果。

mOutputTextureDrawer.draw(mInputSurfaceTexture.getTimestamp() / 1000L);

##### 5.3.3 分发回调 #####

最后会调用`RendererFrameCallback.onRendererFrame`，`RendererFrameCallback`我们刚才已经说过了，带滤镜拍照、录像都实现了这个`RendererFrameCallback`回调，从而来现实拍照和录像的功能，这不是本文的重点，这里我们也先略过，后续文章中会详细讲解。

for (RendererFrameCallback callback : mRendererFrameCallbacks) {
        
        callback.onRendererFrame(mInputSurfaceTexture, mDrawRotation, mCropScaleX, mCropScaleY);
    }

### 6. 其他 ###

#### 6.1 CameraView源码解析系列 ####

[Android 相机库CameraView源码解析 (一) : 预览-CSDN博客][Android _CameraView_ _ _]  
[Android 相机库CameraView源码解析 (二) : 拍照-CSDN博客][Android _CameraView_ _ _ _-CSDN]  
[Android 相机库CameraView源码解析 (三) : 滤镜相关类说明-CSDN博客][Link 1]  
[Android 相机库CameraView源码解析 (四) : 带滤镜预览-CSDN博客][Android _CameraView_ _ _ _-CSDN 1]  
[Android 相机库CameraView源码解析 (五) : 带滤镜拍照-CSDN博客][Android _CameraView_ _ _ _-CSDN 2]  
[Android 相机库CameraView源码解析 (六) : 保存滤镜效果-CSDN博客][Android _CameraView_ _ _ _-CSDN 3]

[natario1_CameraView]: https://github.com/natario1/CameraView
[Link 1]: https://blog.csdn.net/EthanCo/article/details/134517249
[c92f5c122cb6428ba2fa01c2f4421049.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/25/5507fa6ba7a14dc1b7c7d063ba012618.png
[Android _CameraView_ _ _]: https://blog.csdn.net/EthanCo/article/details/134511622
[Android _CameraView_ _ _ _-CSDN]: https://blog.csdn.net/EthanCo/article/details/134545086
[Android _CameraView_ _ _ _-CSDN 1]: https://blog.csdn.net/EthanCo/article/details/135202176
[Android _CameraView_ _ _ _-CSDN 2]: https://blog.csdn.net/EthanCo/article/details/134517154
[Android _CameraView_ _ _ _-CSDN 3]: https://blog.csdn.net/EthanCo/article/details/134691849