android:GLSurfaceView绘制bitmap图片及glViewport调整的效果
首先看一下GLSurfaceView是怎样绘制的。正如android开发文档中描写叙述的那样,我们须要new一个GLSurfaceView对象,然后设置一个实现了Renderer接口的对象,我们须要写一个MyRender类,实现Renderer的方法等等。我们先看一下Activity的写法。它不须要一个布局文件,我们将GLSurfaceView对象作为activity的contentview就可以。例如以下:
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)); } }
以下,我们主要看一下MyGLRender类的写法,它实现了Renderer接口,详细例如以下:
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,这里主要实现了例如以下三个方法:onSurfaceCreated,onSurfaceChanged和onDrawFrame,当中,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能够看出,我们首先须要载入一个图片资源,然后生成texture。在这里,特别说明一下changeGLViewport这种方法,假设在MyRender里面去掉这种方法,执行结果是,GLSurfaceView绘制出一张图片。加入这种方法以后,则是周期性得绘制一个由远到近的一个“动画”。注意,这样的动画,并没有改变图像本身,并且调整不通的视角产生的,因此效率非常高。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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