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android:GLSurfaceView绘制bitmap图片及glViewport调整的效果
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：
package net.mobctrl.glsurfaceviewbmp;
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));
}
}
下面，我们主要看一下MyGLRender类的写法，它实现了Renderer接口，具体如下：
package net.mobctrl.glsurfaceviewbmp;
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。
package net.mobctrl.glsurfaceviewbmp;
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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android:GLSurfaceView绘制bitmap图片及glViewport调整的效果
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