Android多种方式实现相机圆形预览

效果图如下：

TextureView + GLSurfaceView，1088x1088	TextureView + GLSurfaceView，1920x1080

一、为预览控件设置圆角

为控件设置ViewOutlineProvider

 public RoundTextureView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setOutlineProvider(new ViewOutlineProvider() {
            @Override
            public void getOutline(View view, Outline outline) {
                Rect rect = new Rect(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
                outline.setRoundRect(rect, radius);
            }
        });
        setClipToOutline(true);
    }

在需要时修改圆角值并更新

    public void setRadius(int radius) {
        this.radius = radius;
    }

    public void turnRound() {
        invalidateOutline();
    }

即可根据设置的圆角值更新控件显示的圆角大小。当控件为正方形，且圆角值为边长的一半，显示的就是圆形。

二、实现正方形预览

1. 设备支持1:1预览尺寸

首先介绍一种简单但是局限性较大的实现方式：将相机预览尺寸和预览控件的大小都调整为1:1。

一般Android设备都支持多种预览尺寸，以Samsung Tab S3为例

• 在使用Camera API时，其支持的预览尺寸如下：

2019-08-02 13:16:08.669 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 1920x1080
2019-08-02 13:16:08.669 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 1280x720
2019-08-02 13:16:08.669 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 1440x1080
2019-08-02 13:16:08.669 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 1088x1088
2019-08-02 13:16:08.670 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 1056x864
2019-08-02 13:16:08.670 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 960x720
2019-08-02 13:16:08.670 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 720x480
2019-08-02 13:16:08.670 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 640x480
2019-08-02 13:16:08.670 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 352x288
2019-08-02 13:16:08.670 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 320x240
2019-08-02 13:16:08.670 16407-16407/com.wsy.glcamerademo I/CameraHelper: supportedPreviewSize: 176x144

其中1:1的预览尺寸为：1088x1088。

• 在使用Camera2 API时，其支持的预览尺寸（其实也包含了PictureSize）如下：

2019-08-02 13:19:24.980 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 4128x3096
2019-08-02 13:19:24.980 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 4128x2322
2019-08-02 13:19:24.980 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 3264x2448
2019-08-02 13:19:24.980 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 3264x1836
2019-08-02 13:19:24.980 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 3024x3024
2019-08-02 13:19:24.980 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2976x2976
2019-08-02 13:19:24.980 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2880x2160
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2592x1944
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2560x1920
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2560x1440
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2560x1080
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2160x2160
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2048x1536
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 2048x1152
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 1936x1936
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 1920x1080
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 1440x1080
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 1280x960
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 1280x720
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 960x720
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 720x480
2019-08-02 13:19:24.981 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 640x480
2019-08-02 13:19:24.982 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 320x240
2019-08-02 13:19:24.982 16768-16768/com.wsy.glcamerademo I/Camera2Helper: getBestSupportedSize: 176x144

其中1:1的预览尺寸为：3024x3024、2976x2976、2160x2160、1936x1936。

只要我们选择1:1的预览尺寸，再将预览控件设置为正方形，即可实现正方形预览；
再通过设置预览控件的圆角为边长的一半，即可实现圆形预览。

2. 设备不支持1:1预览尺寸的情况

• 选择1:1预览尺寸的缺陷分析

  • 分辨率局限性
    上述说到，我们可以选择1:1的预览尺寸进行预览，但是局限性较高，
    可选择范围都很小。如果相机不支持1:1的预览尺寸，这个方案就不可行了。
  • 资源消耗
    以Samsung tab S3为例，该设备使用Camera2 API时，支持的正方形预览尺寸都很大，在进行图像处理等操作时将占用较多系统资源。

• 处理不支持1:1预览尺寸的情况

  • 添加一个1:1尺寸的ViewGroup
  • 将TextureView放入ViewGroup
  • 设置TextureView的margin值以达到显示中心正方形区域的效果

示意图

示例代码

    //将预览控件和预览尺寸比例保持一致，避免拉伸
    {
        FrameLayout.LayoutParams textureViewLayoutParams = (FrameLayout.LayoutParams) textureView.getLayoutParams();
        int newHeight = 0;
        int newWidth = textureViewLayoutParams.width;
        //横屏
        if (displayOrientation % 180 == 0) {
            newHeight = textureViewLayoutParams.width * previewSize.height / previewSize.width;
        }
        //竖屏
        else {
            newHeight = textureViewLayoutParams.width * previewSize.width / previewSize.height;
        }
        ////当不是正方形预览的情况下，添加一层ViewGroup限制View的显示区域
        if (newHeight != textureViewLayoutParams.height) {
           insertFrameLayout = new RoundFrameLayout(CoverByParentCameraActivity.this);
           int sideLength = Math.min(newWidth, newHeight);
           FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(sideLength, sideLength);
           insertFrameLayout.setLayoutParams(layoutParams);
           FrameLayout parentView = (FrameLayout) textureView.getParent();
           parentView.removeView(textureView);
           parentView.addView(insertFrameLayout);

           insertFrameLayout.addView(textureView);
           FrameLayout.LayoutParams newTextureViewLayoutParams = new FrameLayout.LayoutParams(newWidth, newHeight);
           //横屏
           if (displayOrientation % 180 == 0) {
               newTextureViewLayoutParams.leftMargin = ((newHeight - newWidth) / 2);
           }
           //竖屏
           else {
               newTextureViewLayoutParams.topMargin = -(newHeight - newWidth) / 2;
           }
           textureView.setLayoutParams(newTextureViewLayoutParams);
        }
    }

三、使用GLSurfaceView进行自定义程度更高的预览

使用上面的方法操作已经可完成正方形和圆形预览，但是仅适用于原生相机，当我们的数据源并非是原生相机的情况时如何进行圆形预览？接下来介绍使用GLSurfaceView显示NV21的方案，完全是自己实现预览数据的绘制。

1. GLSurfaceView使用流程

OpenGL渲染YUV数据流程

其中的重点是渲染器（Renderer）的编写，Renderer的介绍如下：

   /**
     * A generic renderer interface.
     * 

     * The renderer is responsible for making OpenGL calls to render a frame.
     * 

     * GLSurfaceView clients typically create their own classes that implement
     * this interface, and then call {@link GLSurfaceView#setRenderer} to
     * register the renderer with the GLSurfaceView.
     * 

     *
     * 

     * 
Developer Guides
     * 
For more information about how to use OpenGL, read the
     * OpenGL developer guide.
     * 
     *
     * 
Threading
     * The renderer will be called on a separate thread, so that rendering
     * performance is decoupled from the UI thread. Clients typically need to
     * communicate with the renderer from the UI thread, because that's where
     * input events are received. Clients can communicate using any of the
     * standard Java techniques for cross-thread communication, or they can
     * use the {@link GLSurfaceView#queueEvent(Runnable)} convenience method.
     * 

     * 
EGL Context Lost
     * There are situations where the EGL rendering context will be lost. This
     * typically happens when device wakes up after going to sleep. When
     * the EGL context is lost, all OpenGL resources (such as textures) that are
     * associated with that context will be automatically deleted. In order to
     * keep rendering correctly, a renderer must recreate any lost resources
     * that it still needs. The {@link #onSurfaceCreated(GL10, EGLConfig)} method
     * is a convenient place to do this.
     *
     *
     * @see #setRenderer(Renderer)
     */
    public interface Renderer {
        /**
         * Called when the surface is created or recreated.
         * 

         * Called when the rendering thread
         * starts and whenever the EGL context is lost. The EGL context will typically
         * be lost when the Android device awakes after going to sleep.
         * 

         * Since this method is called at the beginning of rendering, as well as
         * every time the EGL context is lost, this method is a convenient place to put
         * code to create resources that need to be created when the rendering
         * starts, and that need to be recreated when the EGL context is lost.
         * Textures are an example of a resource that you might want to create
         * here.
         * 

         * Note that when the EGL context is lost, all OpenGL resources associated
         * with that context will be automatically deleted. You do not need to call
         * the corresponding "glDelete" methods such as glDeleteTextures to
         * manually delete these lost resources.
         * 

         * @param gl the GL interface. Use instanceof to
         * test if the interface supports GL11 or higher interfaces.
         * @param config the EGLConfig of the created surface. Can be used
         * to create matching pbuffers.
         */
        void onSurfaceCreated(GL10 gl, EGLConfig config);

        /**
         * Called when the surface changed size.
         * 

         * Called after the surface is created and whenever
         * the OpenGL ES surface size changes.
         * 

         * Typically you will set your viewport here. If your camera
         * is fixed then you could also set your projection matrix here:
         * 
         * void onSurfaceChanged(GL10 gl, int width, int height) {
         *     gl.glViewport(0, 0, width, height);
         *     // for a fixed camera, set the projection too
         *     float ratio = (float) width / height;
         *     gl.glMatrixMode(GL10.GL_PROJECTION);
         *     gl.glLoadIdentity();
         *     gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10);
         * }
         * 
         * @param gl the GL interface. Use instanceof to
         * test if the interface supports GL11 or higher interfaces.
         * @param width
         * @param height
         */
        void onSurfaceChanged(GL10 gl, int width, int height);

        /**
         * Called to draw the current frame.
         * 

         * This method is responsible for drawing the current frame.
         * 

         * The implementation of this method typically looks like this:
         * 
         * void onDrawFrame(GL10 gl) {
         *     gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
         *     //... other gl calls to render the scene ...
         * }
         * 
         * @param gl the GL interface. Use instanceof to
         * test if the interface supports GL11 or higher interfaces.
         */
        void onDrawFrame(GL10 gl);
    }

• void onSurfaceCreated(GL10 gl, EGLConfig config)
  在Surface创建或重建的情况下回调
• void onSurfaceChanged(GL10 gl, int width, int height)
  在Surface的大小发生变化的情况下回调
• void onDrawFrame(GL10 gl)
  在这里实现绘制操作。当我们设置的renderMode为RENDERMODE_CONTINUOUSLY时，该函数将不断地执行；
  当我们设置的renderMode为RENDERMODE_WHEN_DIRTY时，将只在创建完成和调用requestRender后才执行。一般我们选择RENDERMODE_WHEN_DIRTY渲染模式，避免过度绘制。

一般情况下，我们会自己实现一个Renderer，然后为GLSurfaceView设置Renderer，可以说，Renderer的编写是整个流程的核心步骤。以下是在void onSurfaceCreated(GL10 gl, EGLConfig config)进行的初始化操作和在void onDrawFrame(GL10 gl)进行的绘制操作的流程图：

渲染YUV数据的Renderer

2. 具体实现

• 坐标系介绍

Android View坐标系	OpenGL世界坐标系

如图所示，和Android的View坐标系不同，OpenGL的坐标系是笛卡尔坐标系。
Android View的坐标系以左上角为原点，向右x递增，向下y递增；
而OpenGL坐标系以中心为原点，向右x递增，向上y递增。

• 着色器编写

    /**
     * 顶点着色器
     */
    private static String VERTEX_SHADER =
            "    attribute vec4 attr_position;\n" +
                    "    attribute vec2 attr_tc;\n" +
                    "    varying vec2 tc;\n" +
                    "    void main() {\n" +
                    "        gl_Position = attr_position;\n" +
                    "        tc = attr_tc;\n" +
                    "    }";

    /**
     * 片段着色器
     */
    private static String FRAG_SHADER =
            "    varying vec2 tc;\n" +
                    "    uniform sampler2D ySampler;\n" +
                    "    uniform sampler2D uSampler;\n" +
                    "    uniform sampler2D vSampler;\n" +
                    "    const mat3 convertMat = mat3( 1.0, 1.0, 1.0, -0.001, -0.3441, 1.772, 1.402, -0.7141, -0.58060);\n" +
                    "    void main()\n" +
                    "    {\n" +
                    "        vec3 yuv;\n" +
                    "        yuv.x = texture2D(ySampler, tc).r;\n" +
                    "        yuv.y = texture2D(uSampler, tc).r - 0.5;\n" +
                    "        yuv.z = texture2D(vSampler, tc).r - 0.5;\n" +
                    "        gl_FragColor = vec4(convertMat * yuv, 1.0);\n" +
                    "    }";

• 内建变量解释

  • gl_Position
VERTEX_SHADER代码里的gl_Position代表绘制的空间坐标。由于我们是二维绘制，所以直接传入OpenGL二维坐标系的左下(-1,-1)、右下(1,-1)、左上(-1,1)、右上(1,1)，也就是{-1,-1,1,-1,-1,1,1,1}
  • gl_FragColor
FRAG_SHADER代码里的gl_FragColor代表单个片元的颜色

• 其他变量解释

  • ySampler、uSampler、vSampler
    分别代表Y、U、V纹理采样器
  • convertMat
    根据以下公式：

    R = Y + 1.402 (V - 128)
    G = Y - 0.34414 (U - 128) - 0.71414 (V - 128)
    B = Y + 1.772 (U - 128)
    

    我们可得到一个YUV转RGB的矩阵

    1.0,    1.0,    1.0, 
    0,     -0.344,  1.77, 
    1.403, -0.714,  0 
    

• 部分类型、函数的解释

  • vec3、vec4
    分别代表三维向量、四维向量。
  • vec4 texture2D(sampler2D sampler, vec2 coord)
    以指定的矩阵将采样器的图像纹理转换为颜色值；如：
    texture2D(ySampler, tc).r获取到的是Y数据，
    texture2D(uSampler, tc).r获取到的是U数据，
    texture2D(vSampler, tc).r获取到的是V数据。

• 在Java代码中进行初始化
  根据图像宽高创建Y、U、V对应的ByteBuffer纹理数据；
  根据是否镜像显示、旋转角度选择对应的转换矩阵；

  public void init(boolean isMirror, int rotateDegree, int frameWidth, int frameHeight) {
      if (this.frameWidth == frameWidth
              && this.frameHeight == frameHeight
              && this.rotateDegree == rotateDegree
              && this.isMirror == isMirror) {
          return;
      }
      dataInput = false;
      this.frameWidth = frameWidth;
      this.frameHeight = frameHeight;
      this.rotateDegree = rotateDegree;
      this.isMirror = isMirror;
      yArray = new byte[this.frameWidth * this.frameHeight];
      uArray = new byte[this.frameWidth * this.frameHeight / 4];
      vArray = new byte[this.frameWidth * this.frameHeight / 4];
  
      int yFrameSize = this.frameHeight * this.frameWidth;
      int uvFrameSize = yFrameSize >> 2;
      yBuf = ByteBuffer.allocateDirect(yFrameSize);
      yBuf.order(ByteOrder.nativeOrder()).position(0);
  
      uBuf = ByteBuffer.allocateDirect(uvFrameSize);
      uBuf.order(ByteOrder.nativeOrder()).position(0);
  
      vBuf = ByteBuffer.allocateDirect(uvFrameSize);
      vBuf.order(ByteOrder.nativeOrder()).position(0);
      // 顶点坐标
      squareVertices = ByteBuffer
              .allocateDirect(GLUtil.SQUARE_VERTICES.length * FLOAT_SIZE_BYTES)
              .order(ByteOrder.nativeOrder())
              .asFloatBuffer();
      squareVertices.put(GLUtil.SQUARE_VERTICES).position(0);
      //纹理坐标
      if (isMirror) {
          switch (rotateDegree) {
              case 0:
                  coordVertice = GLUtil.MIRROR_COORD_VERTICES;
                  break;
              case 90:
                  coordVertice = GLUtil.ROTATE_90_MIRROR_COORD_VERTICES;
                  break;
              case 180:
                  coordVertice = GLUtil.ROTATE_180_MIRROR_COORD_VERTICES;
                  break;
              case 270:
                  coordVertice = GLUtil.ROTATE_270_MIRROR_COORD_VERTICES;
                  break;
              default:
                  break;
          }
      } else {
          switch (rotateDegree) {
              case 0:
                  coordVertice = GLUtil.COORD_VERTICES;
                  break;
              case 90:
                  coordVertice = GLUtil.ROTATE_90_COORD_VERTICES;
                  break;
              case 180:
                  coordVertice = GLUtil.ROTATE_180_COORD_VERTICES;
                  break;
              case 270:
                  coordVertice = GLUtil.ROTATE_270_COORD_VERTICES;
                  break;
              default:
                  break;
          }
      }
      coordVertices = ByteBuffer.allocateDirect(coordVertice.length * FLOAT_SIZE_BYTES).order(ByteOrder.nativeOrder()).asFloatBuffer();
      coordVertices.put(coordVertice).position(0);
  }
  

  在Surface创建完成时进行Renderer初始化

     private void initRenderer() {
          rendererReady = false;
          createGLProgram();
  
          //启用纹理
          GLES20.glEnable(GLES20.GL_TEXTURE_2D);
          //创建纹理
          createTexture(frameWidth, frameHeight, GLES20.GL_LUMINANCE, yTexture);
          createTexture(frameWidth / 2, frameHeight / 2, GLES20.GL_LUMINANCE, uTexture);
          createTexture(frameWidth / 2, frameHeight / 2, GLES20.GL_LUMINANCE, vTexture);
  
          rendererReady = true;
      }  
  

  其中createGLProgram用于创建OpenGL Program并关联着色器代码中的变量

    private void createGLProgram() {
        int programHandleMain = GLUtil.createShaderProgram();
        if (programHandleMain != -1) {
            // 使用着色器程序
            GLES20.glUseProgram(programHandleMain);
            // 获取顶点着色器变量
            int glPosition = GLES20.glGetAttribLocation(programHandleMain, "attr_position");
            int textureCoord = GLES20.glGetAttribLocation(programHandleMain, "attr_tc");
  
            // 获取片段着色器变量
            int ySampler = GLES20.glGetUniformLocation(programHandleMain, "ySampler");
            int uSampler = GLES20.glGetUniformLocation(programHandleMain, "uSampler");
            int vSampler = GLES20.glGetUniformLocation(programHandleMain, "vSampler");
  
            //给变量赋值
            /**
             * GLES20.GL_TEXTURE0 和 ySampler 绑定
             * GLES20.GL_TEXTURE1 和 uSampler 绑定
             * GLES20.GL_TEXTURE2 和 vSampler 绑定
             *
             * 也就是说 glUniform1i的第二个参数代表图层序号
             */
            GLES20.glUniform1i(ySampler, 0);
            GLES20.glUniform1i(uSampler, 1);
            GLES20.glUniform1i(vSampler, 2);
  
            GLES20.glEnableVertexAttribArray(glPosition);
            GLES20.glEnableVertexAttribArray(textureCoord);
  
            /**
             * 设置Vertex Shader数据
             */
            squareVertices.position(0);
            GLES20.glVertexAttribPointer(glPosition, GLUtil.COUNT_PER_SQUARE_VERTICE, GLES20.GL_FLOAT, false, 8, squareVertices);
            coordVertices.position(0);
            GLES20.glVertexAttribPointer(textureCoord, GLUtil.COUNT_PER_COORD_VERTICES, GLES20.GL_FLOAT, false, 8, coordVertices);
        }
    }
  

  其中createTexture用于根据宽高和格式创建纹理

        private void createTexture(int width, int height, int format, int[] textureId) {
            //创建纹理
            GLES20.glGenTextures(1, textureId, 0);
            //绑定纹理
            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId[0]);
            /**
             * {@link GLES20#GL_TEXTURE_WRAP_S}代表左右方向的纹理环绕模式
             * {@link GLES20#GL_TEXTURE_WRAP_T}代表上下方向的纹理环绕模式
             *
             *  {@link GLES20#GL_REPEAT}：重复
             *  {@link GLES20#GL_MIRRORED_REPEAT}：镜像重复
             *  {@link GLES20#GL_CLAMP_TO_EDGE}：忽略边框截取
             *
             * 例如我们使用{@link GLES20#GL_REPEAT}：
             *
             *             squareVertices           coordVertices
             *             -1.0f, -1.0f,            1.0f, 1.0f,
             *             1.0f, -1.0f,             1.0f, 0.0f,         ->          和textureView预览相同
             *             -1.0f, 1.0f,             0.0f, 1.0f,
             *             1.0f, 1.0f               0.0f, 0.0f
             *
             *             squareVertices           coordVertices
             *             -1.0f, -1.0f,            2.0f, 2.0f,
             *             1.0f, -1.0f,             2.0f, 0.0f,         ->          和textureView预览相比，分割成了4 块相同的预览（左下，右下，左上，右上）
             *             -1.0f, 1.0f,             0.0f, 2.0f,
             *             1.0f, 1.0f               0.0f, 0.0f
             */
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_REPEAT);
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_REPEAT);
            /**
             * {@link GLES20#GL_TEXTURE_MIN_FILTER}代表所显示的纹理比加载进来的纹理小时的情况
             * {@link GLES20#GL_TEXTURE_MAG_FILTER}代表所显示的纹理比加载进来的纹理大时的情况
             *
             *  {@link GLES20#GL_NEAREST}：使用纹理中坐标最接近的一个像素的颜色作为需要绘制的像素颜色
             *  {@link GLES20#GL_LINEAR}：使用纹理中坐标最接近的若干个颜色，通过加权平均算法得到需要绘制的像素颜色
             */
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
            GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);
            GLES20.glTexImage2D(GLES20.GL_TEXTURE_2D, 0, format, width, height, 0, format, GLES20.GL_UNSIGNED_BYTE, null);
        }
  

  • 在Java代码中调用绘制

  在数据源获取到时裁剪并传入帧数据

   @Override
    public void onPreview(final byte[] nv21, Camera camera) {
        //裁剪指定的图像区域
        ImageUtil.cropNV21(nv21, this.squareNV21, previewSize.width, previewSize.height, cropRect);
        //刷新GLSurfaceView
        roundCameraGLSurfaceView.refreshFrameNV21(this.squareNV21);
    }
  

  NV21数据裁剪代码

    /**
     * 裁剪NV21数据
     *
     * @param originNV21 原始的NV21数据
     * @param cropNV21   裁剪结果NV21数据，需要预先分配内存
     * @param width      原始数据的宽度
     * @param height     原始数据的高度
     * @param left       原始数据被裁剪的区域的左边界
     * @param top        原始数据被裁剪的区域的上边界
     * @param right      原始数据被裁剪的区域的右边界
     * @param bottom     原始数据被裁剪的区域的下边界
     */
    public static void cropNV21(byte[] originNV21, byte[] cropNV21, int width, int height, int left, int top, int right, int bottom) {
        int halfWidth = width / 2;
        int cropImageWidth = right - left;
        int cropImageHeight = bottom - top;
  
        //原数据Y左上
        int originalYLineStart = top * width;
        int targetYIndex = 0;
  
        //原数据UV左上
        int originalUVLineStart = width * height + top * halfWidth;
  
        //目标数据的UV起始值
        int targetUVIndex = cropImageWidth * cropImageHeight;
  
        for (int i = top; i < bottom; i++) {
            System.arraycopy(originNV21, originalYLineStart + left, cropNV21, targetYIndex, cropImageWidth);
            originalYLineStart += width;
            targetYIndex += cropImageWidth;
            if ((i & 1) == 0) {
                System.arraycopy(originNV21, originalUVLineStart + left, cropNV21, targetUVIndex, cropImageWidth);
                originalUVLineStart += width;
                targetUVIndex += cropImageWidth;
            }
        }
    }
  

  传给GLSurafceView并刷新帧数据

    /**
     * 传入NV21刷新帧
     *
     * @param data NV21数据
     */
    public void refreshFrameNV21(byte[] data) {
        if (rendererReady) {
            yBuf.clear();
            uBuf.clear();
            vBuf.clear();
            putNV21(data, frameWidth, frameHeight);
            dataInput = true;
            requestRender();
        }
    }
  

  其中putNV21用于将NV21中的Y、U、V数据分别取出

    /**
     * 将NV21数据的Y、U、V分量取出
     *
     * @param src    nv21帧数据
     * @param width  宽度
     * @param height 高度
     */
    private void putNV21(byte[] src, int width, int height) {
  
        int ySize = width * height;
        int frameSize = ySize * 3 / 2;
  
        //取分量y值
        System.arraycopy(src, 0, yArray, 0, ySize);
  
        int k = 0;
  
        //取分量uv值
        int index = ySize;
        while (index < frameSize) {
            vArray[k] = src[index++];
            uArray[k++] = src[index++];
        }
        yBuf.put(yArray).position(0);
        uBuf.put(uArray).position(0);
        vBuf.put(vArray).position(0);
    }
  

  在执行requestRender后，onDrawFrame函数将被回调，在其中进行三个纹理的数据绑定并绘制

        @Override
        public void onDrawFrame(GL10 gl) {
            // 分别对每个纹理做激活、绑定、设置数据操作
            if (dataInput) {
                //y
                GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
                GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, yTexture[0]);
                GLES20.glTexSubImage2D(GLES20.GL_TEXTURE_2D,
                        0,
                        0,
                        0,
                        frameWidth,
                        frameHeight,
                        GLES20.GL_LUMINANCE,
                        GLES20.GL_UNSIGNED_BYTE,
                        yBuf);
  
                //u
                GLES20.glActiveTexture(GLES20.GL_TEXTURE1);
                GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, uTexture[0]);
                GLES20.glTexSubImage2D(GLES20.GL_TEXTURE_2D,
                        0,
                        0,
                        0,
                        frameWidth >> 1,
                        frameHeight >> 1,
                        GLES20.GL_LUMINANCE,
                        GLES20.GL_UNSIGNED_BYTE,
                        uBuf);
  
                //v
                GLES20.glActiveTexture(GLES20.GL_TEXTURE2);
                GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, vTexture[0]);
                GLES20.glTexSubImage2D(GLES20.GL_TEXTURE_2D,
                        0,
                        0,
                        0,
                        frameWidth >> 1,
                        frameHeight >> 1,
                        GLES20.GL_LUMINANCE,
                        GLES20.GL_UNSIGNED_BYTE,
                        vBuf);
                //在数据绑定完成后进行绘制
                GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
            }
        }
  

  即可完成绘制。

四、加一层边框

有时候需求并不仅仅是圆形预览这么简单，我们可能还要为相机预览加一层边框

边框效果

一样的思路，我们动态地修改边框值，并进行重绘。
边框自定义View中的相关代码如下：

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (paint == null) {
            paint = new Paint();
            paint.setStyle(Paint.Style.STROKE);
            paint.setAntiAlias(true);
            SweepGradient sweepGradient = new SweepGradient(((float) getWidth() / 2), ((float) getHeight() / 2),
                    new int[]{Color.GREEN, Color.CYAN, Color.BLUE, Color.CYAN, Color.GREEN}, null);
            paint.setShader(sweepGradient);
        }
        drawBorder(canvas, 6);
    }


    private void drawBorder(Canvas canvas, int rectThickness) {
        if (canvas == null) {
            return;
        }
        paint.setStrokeWidth(rectThickness);
        Path drawPath = new Path();
        drawPath.addRoundRect(new RectF(0, 0, getWidth(), getHeight()), radius, radius, Path.Direction.CW);
        canvas.drawPath(drawPath, paint);
    }

    public void turnRound() {
        invalidate();
    }

    public void setRadius(int radius) {
        this.radius = radius;
    }

五、完整Demo代码：

https://github.com/wangshengyang1996/GLCameraDemo

• 使用Camera API和Camera2 API并选择最接近正方形的预览尺寸
• 使用Camera API并为其动态添加一层父控件，达到正方形预览的效果
• 使用Camera API获取预览数据，使用OpenGL的方式进行显示