【OpenGL】GLSurfaceView绘制bitmap图片及glViewport调整的效果

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首先看一下GLSurfaceView是如何绘制的。正如android开发文档中描述的那样，我们需要new一个GLSurfaceView对象，然后设置一个实现了Renderer接口的对象，我们需要写一个MyRender类，实现Renderer的方法等等。我们先看一下Activity的写法。它不需要一个布局文件，我们将GLSurfaceView对象作为activity的contentview即可。如下：

import java.util.Random; import android.annotation.SuppressLint;import android.app.Activity;import android.opengl.GLSurfaceView;import android.os.Bundle;import android.view.WindowManager; /** *  * @author Zheng Haibo * @web http://www.mobctrl.net * */public class MainActivity extends Activity {     private GLSurfaceView glView; // Use GLSurfaceView    Random rnd = new Random();     @SuppressLint("NewApi")    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setTheme(android.R.style.Theme_Translucent_NoTitleBar);        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);        glView = new GLSurfaceView(this); // Allocate a GLSurfaceView        glView.setRenderer(new MyGLRenderer(this)); // Use a custom renderer        glView.getAlpha();        this.setContentView(glView);      }     @Override    protected void onPause() {        super.onPause();        glView.onPause();    }     @Override    protected void onResume() {        super.onResume();        glView.onResume();        android.provider.Settings.System.putInt(this.getContentResolver(),                android.provider.Settings.System.SCREEN_BRIGHTNESS,                rnd.nextInt(256));     }}

import java.util.Random; import javax.microedition.khronos.opengles.GL10; import android.content.Context;import android.opengl.GLSurfaceView.Renderer;import android.opengl.GLU; /** * @date 2014年10月20日 下午2:49:17 * @author Zheng Haibo * @Description: TODO */public class MyGLRenderer implements Renderer {    Context context; // Application's context    Random r = new Random();    //private Square square;    private GLBitmap glBitmap;    private int width = 0;    private int height = 0;    private long frameSeq = 0;    private int viewportOffset = 0;    private int maxOffset = 400;     public MyGLRenderer(Context context) {        this.context = context;        //square = new Square();        glBitmap = new GLBitmap();    }     @Override    public void onSurfaceChanged(GL10 gl, int width, int height) {        if (height == 0) { // Prevent A Divide By Zero By            height = 1; // Making Height Equal One        }        this.width = width;        this.height = height;        gl.glViewport(0, 0, width, height); // Reset The                                            // Current        // Viewport        gl.glMatrixMode(GL10.GL_PROJECTION); // Select The Projection Matrix        gl.glLoadIdentity(); // Reset The Projection Matrix         // Calculate The Aspect Ratio Of The Window        GLU.gluPerspective(gl, 45.0f, (float) width / (float) height, 0.1f,                100.0f);         gl.glMatrixMode(GL10.GL_MODELVIEW); // Select The Modelview Matrix        gl.glLoadIdentity();    }     /**     * 每隔16ms调用一次     */    @Override    public void onDrawFrame(GL10 gl) {        gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);        // Reset the Modelview Matrix        gl.glLoadIdentity();        gl.glTranslatef(0.0f, 0.0f, -5.0f); // move 5 units INTO the screen is                                            // the same as moving the camera 5                                            // units away        // square.draw(gl);        glBitmap.draw(gl);        changeGLViewport(gl);    }     /**     * 通过改变gl的视角获取     *      * @param gl     */    private void changeGLViewport(GL10 gl) {        System.out.println("time=" + System.currentTimeMillis());        frameSeq++;        viewportOffset++;        // The        // Current        if (frameSeq % 100 == 0) {// 每隔100帧，重置            gl.glViewport(0, 0, width, height);            viewportOffset = 0;        } else {            int k = 4;            gl.glViewport(-maxOffset + viewportOffset * k, -maxOffset                    + viewportOffset * k, this.width - viewportOffset * 2 * k                    + maxOffset * 2, this.height - viewportOffset * 2 * k                    + maxOffset * 2);        }    }     @Override    public void onSurfaceCreated(GL10 gl,            javax.microedition.khronos.egl.EGLConfig arg1) {        glBitmap.loadGLTexture(gl, this.context);         gl.glEnable(GL10.GL_TEXTURE_2D); // Enable Texture Mapping ( NEW )        gl.glShadeModel(GL10.GL_SMOOTH); // Enable Smooth Shading        gl.glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black Background        gl.glClearDepthf(1.0f); // Depth Buffer Setup        gl.glEnable(GL10.GL_DEPTH_TEST); // Enables Depth Testing        gl.glDepthFunc(GL10.GL_LEQUAL); // The Type Of Depth Testing To Do         gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST);    }}

注意，这里主要实现了如下三个方法：onSurfaceCreated，onSurfaceChanged和onDrawFrame，其中，关键就是onDrawFrame方法，它的绘制机制是：1s的时间内，onDrawFrame方法会调用60次，大约每隔16ms调用一次。我们先看里面的glBitmap对象，changeGLViewport方法待会再说。

import java.nio.ByteBuffer;import java.nio.ByteOrder;import java.nio.FloatBuffer; import javax.microedition.khronos.opengles.GL10; import net.mobctrl.glsurfaceviewbmp.R;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.opengl.GLUtils; /** * @date 2014年10月20日 下午3:09:33 * @author Zheng Haibo * @Description: TODO */public class GLBitmap {    private FloatBuffer textureBuffer; // buffer holding the texture coordinates    private float texture[] = {            // Mapping coordinates for the vertices            0.0f, 1.0f, // top left (V2)            0.0f, 0.0f, // bottom left (V1)            1.0f, 1.0f, // top right (V4)            1.0f, 0.0f // bottom right (V3)    };     private FloatBuffer vertexBuffer; // buffer holding the vertices     private float vertices[] = { -1.0f, -1.0f, 0.0f, // V1 - bottom left            -1.0f, 1.0f, 0.0f, // V2 - top left            1.0f, -1.0f, 0.0f, // V3 - bottom right            1.0f, 1.0f, 0.0f // V4 - top right    };     public GLBitmap() {        ByteBuffer byteBuffer = ByteBuffer.allocateDirect(vertices.length * 4);        byteBuffer.order(ByteOrder.nativeOrder());        vertexBuffer = byteBuffer.asFloatBuffer();        vertexBuffer.put(vertices);        vertexBuffer.position(0);         byteBuffer = ByteBuffer.allocateDirect(texture.length * 4);        byteBuffer.order(ByteOrder.nativeOrder());        textureBuffer = byteBuffer.asFloatBuffer();        textureBuffer.put(texture);        textureBuffer.position(0);    }     /** The texture pointer */    private int[] textures = new int[1];     public void loadGLTexture(GL10 gl, Context context) {        // loading texture        Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(),                R.drawable.plane_image);         // generate one texture pointer        gl.glGenTextures(1, textures, 0);        // ...and bind it to our array        gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);         // create nearest filtered texture        gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER,                GL10.GL_NEAREST);        gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER,                GL10.GL_LINEAR);         // Use Android GLUtils to specify a two-dimensional texture image from        // our bitmap        GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);         // Clean up        bitmap.recycle();    }     public void draw(GL10 gl) {        // bind the previously generated texture        gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);         // Point to our buffers        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);        gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);         // Set the face rotation        gl.glFrontFace(GL10.GL_CW);         // Point to our vertex buffer        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);        gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);         // Draw the vertices as triangle strip        gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);         // Disable the client state before leaving        gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);        gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);    } }

从GLBitmap可以看出，我们首先需要加载一个图片资源，然后生成texture。在这里，特别说明一下changeGLViewport这个方法，如果在MyRender里面去掉这个方法，运行结果是，GLSurfaceView绘制出一张图片。添加这个方法以后，则是周期性得绘制一个由远到近的一个“动画”。注意，这种动画，并没有改变图像本身，而且调整不通的视角产生的，因此效率很高。它的原理，就像你拿一个相机，去拍摄墙壁上得一幅画，相机离画越来越近时，画面在放大，而墙壁本身并没有变化。

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