本章在第三章(Opengl ES 1.x NDK例項開發之三:多邊形的旋轉)的基礎上演示如何使用紋理貼圖，分別實現了三角形紋理貼圖和正方形紋理貼圖。

【例項講解】

OpenglES要求生成紋理的圖片長寬為2的n次方，支援各種格式(BMP, GIF, JPEG, PNG...)

本例中使用的圖片為png格式，尺寸為128*128

本例中，在上層GLJNIView.java中生成紋理，將紋理控制代碼傳遞給Native層進行繪製，詳見

private void genTexture(GL10 gl, Context context)

【例項原始碼】

[GLJNIActivity.java]

1. /*
    
2.  * Copyright (C) 2007 The Android Open Source Project 
3.  * 
4.  * Licensed under the Apache License, Version 2.0 (the "License"); 
5.  * you may not use this file except in compliance with the License. 
6.  * You may obtain a copy of the License at 
7.  * 
8.  *      http://www.apache.org/licenses/LICENSE-2.0 
9.  * 
10.  * Unless required by applicable law or agreed to in writing, software
     
11.  * distributed under the License is distributed on an "AS IS" BASIS, 
12.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
13.  * See the License for the specific language governing permissions and 
14.  * limitations under the License. 
15.  *  
16.  * author: [email protected] 
17.  */
18. package
     com.android.gljni;  
19. import com.android.gljni.GLJNIView;  
20. import android.app.Activity;  
21. import android.os.Bundle;  
22. publicclass GLJNIActivity extends Activity {  
23.     GLJNIView mView;  
24.     @Override
25.     protectedvoid onCreate(Bundle icicle) {  
26.         super.onCreate(icicle);  
27.         mView = new GLJNIView(getApplication());  
28.         setContentView(mView);  
29.     }  
30.     @Override
31.     protectedvoid onPause() {  
32.         super.onPause();  
33.         mView.onPause();  
34.     }  
35.     @Override
36.     protectedvoid onResume() {  
37.         super.onResume();  
38.         mView.onResume();  
39.     }  
40. }  

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * author: [email protected]
 */

package com.android.gljni;

import java.io.IOException;
import java.io.InputStream;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import com.android.gljni.GLJNILib;
import com.android.gljnidemo06.R;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLSurfaceView;
import android.opengl.GLUtils;
import android.util.Log;

/**
 * A simple GLSurfaceView sub-class that demonstrate how to perform
 * OpenGL ES 1.x rendering into a GL Surface.
 */
public class GLJNIView extends GLSurfaceView {

	private static final String LOG_TAG = GLJNIView.class.getSimpleName();

	private Renderer renderer;

	public GLJNIView(Context context) {
		super(context);

		// setEGLConfigChooser會對fps產生影響
		setEGLConfigChooser(8, 8, 8, 8, 16, 0);

		renderer = new Renderer(context);
		setRenderer(renderer);
	}

	private static class Renderer implements GLSurfaceView.Renderer {
		//用於紋理對映的繫結，並把繫結後的ID傳遞給C++程式碼，供其呼叫
		private int[] mTexture = new int[2];
		//用於載入Bitmap的context
		private Context mContext;
		public Renderer(Context ctx) {
			mContext = ctx;
		}

		public void onDrawFrame(GL10 gl) {
			GLJNILib.step();
		}

		public void onSurfaceChanged(GL10 gl, int width, int height) {
			GLJNILib.resize(width, height);
		}

		public void onSurfaceCreated(GL10 gl, EGLConfig config) {
			//用來繫結Bitmap紋理
			genTexture(gl, mContext);
			//呼叫本地setTexture方法，把紋理繫結的ID傳遞給C++程式碼，以供其呼叫
			GLJNILib.setTexture(mTexture);
			GLJNILib.init();
		}
		
		/**
		 * 載入Bitmap的方法，
		 * 用來從res中載入Bitmap資源
		 * */
		private Bitmap loadBitmap(Context context, int resourceId) {
			InputStream is = context.getResources().openRawResource(resourceId);
			Bitmap bitmap = null;
			try {

				// 利用BitmapFactory生成Bitmap
				bitmap = BitmapFactory.decodeStream(is);
			} finally {
				try {

					// 關閉流
					is.close();
					is = null;
				} catch (IOException e) {
					e.printStackTrace();
				}

			}
			return bitmap;

		}
		
		/**
		 * 繫結Bitmap紋理
		 * */

		private void genTexture(GL10 gl, Context context) {
			//生成紋理
			gl.glGenTextures(2, mTexture, 0);
			//載入Bitmap
			Bitmap bitmap = loadBitmap(context, R.drawable.logo);
			if (bitmap != null) {
				//如果bitmap載入成功，則生成此bitmap的紋理對映
				gl.glBindTexture(GL10.GL_TEXTURE_2D, mTexture[0]);
				//設定紋理對映的屬性
				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_NEAREST);
				//生成紋理對映
				GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);
				//釋放bitmap資源
				bitmap.recycle();
			}

		}
	}

}

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * author: [email protected]
 */

package com.android.gljni;

//Wrapper for native library
public class GLJNILib {
	
	static {
		System.loadLibrary("gljni");
	}

	/**
     * @param width the current view width
     * @param height the current view height
     */
	public static native void resize(int width, int height); 
	
	/**
	 * render 
	 */
    public static native void step();  
    
    /**
     * init
     */
    public static native void init();  
    
    /**
     * set the texture
     * @param texture	texture id
     */
    public static native void setTexture(int[] texture);
}

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * author: 	[email protected]
 * created:	2014/10/20
 * purpose:	紋理的使用
 */

// OpenGL ES 1.x code

#include <jni.h>
#include <android/log.h>

#include <GLES/gl.h>
#include <GLES/glext.h>

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

/************************************************************************/
/*                             定義                                     */
/************************************************************************/

#define  LOG_TAG    "libgljni"
#define  LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

//初始化紋理陣列
GLuint *gTexture = 0;

// 定義π
const GLfloat PI = 3.1415f;

// 旋轉角度
static GLfloat gAngle = 0.0f; 

// 頂點陣列
const GLfloat gVertices[] = {
	0.0f, 1.0f, 0.0f,	// 上
	-1.0f,-1.0f, 0.0f,	// 左下
	1.0f,-1.0f, 0.0f,	// 右下
};

const GLfloat gVerticesSquare[] = {
	-1.0f, -1.0f, 0.0f, // 左下
	1.0f, -1.0f, 0.0f, 	// 右下
	-1.0f, 1.0f, 0.0f, 	// 左上
	1.0f, 1.0f, 0.0f 	// 右上
};

// 紋理座標
// 紋理座標原點會因不同系統環境而有所不同。
// 比如在iOS以及Android上，紋理座標原點（0, 0）是在左上角
// 而在OS X上，紋理座標的原點是在左下角
const GLfloat gTextureCoord[] = {
	0.5f,0.0f,
	0.0f,1.0f,
	1.0f,1.0f,
};

const GLfloat gTextureSquareCoord[] = {
	0.0f,1.0f,
	1.0f,1.0f,
	0.0f,0.0f,
	1.0f,0.0f,
};
/************************************************************************/
/*                             C++程式碼                                  */
/************************************************************************/

static void printGLString(const char *name, GLenum s) {
	const char *v = (const char *) glGetString(s);
	LOGI("GL %s = %s\n", name, v);
}

static void checkGlError(const char* op) {
	for (GLint error = glGetError(); error; error
		= glGetError()) {
			LOGI("after %s() glError (0x%x)\n", op, error);
	}
}

bool init() {
	printGLString("Version", GL_VERSION);
	printGLString("Vendor", GL_VENDOR);
	printGLString("Renderer", GL_RENDERER);
	printGLString("Extensions", GL_EXTENSIONS);

	// 啟用陰影平滑
	glShadeModel(GL_SMOOTH);

	// 黑色背景	
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);	

	// 設定深度快取	
	glClearDepthf(1.0f);

	// 啟用深度測試
	glEnable(GL_DEPTH_TEST);	

	// 所作深度測試的型別	
	glDepthFunc(GL_LEQUAL);	

	// 對透視進行修正	
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	

	return true;
}

static void _gluPerspective(GLfloat fovy, GLfloat aspect, GLfloat zNear, GLfloat zFar)
{
	GLfloat top = zNear * ((GLfloat) tan(fovy * PI / 360.0));
	GLfloat bottom = -top;
	GLfloat left = bottom * aspect;
	GLfloat right = top * aspect;
	glFrustumf(left, right, bottom, top, zNear, zFar);
}

void resize(int width, int height)
{
	// 防止被零除
	if (height==0)								
	{
		height=1;
	}

	// 重置當前的視口
	glViewport(0, 0, width, height);	
	// 選擇投影矩陣	
	glMatrixMode(GL_PROJECTION);	
	// 重置投影矩陣	
	glLoadIdentity();							

	// 設定視口的大小
	_gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	// 選擇模型觀察矩陣
	glMatrixMode(GL_MODELVIEW);	

	// 重置模型觀察矩陣
	glLoadIdentity();							
}

void renderFrame() {
	// 清除螢幕及深度快取
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  
	// 設定背景顏色為黑色
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
	// 重置當前的模型觀察矩陣
	glLoadIdentity();		
	
	// 啟用頂點陣列
	glEnableClientState(GL_VERTEX_ARRAY);
	glTexEnvf (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
	// 紋理設定
	glEnable(GL_TEXTURE_2D);								// 啟用紋理對映
	glBindTexture(GL_TEXTURE_2D, gTexture[0]);				// 選擇紋理
	glEnableClientState(GL_TEXTURE_COORD_ARRAY);			// 啟用紋理座標陣列

	// 繪製三角形
	glTranslatef(0.0f,2.0f,-10.0f);							// 設定三角形位置
	glRotatef(gAngle,0.0f,1.0f,0.0f);						// 旋轉三角形
	glVertexPointer(3, GL_FLOAT, 0, gVertices);				// 指定頂點陣列
	glTexCoordPointer(2, GL_FLOAT, 0, gTextureCoord);		// 設定紋理座標
	glDrawArrays(GL_TRIANGLES, 0, 3);						// 繪製三角形

	// 繪製正方形
	glTranslatef(0.0f,-4.0f,0.0f);							// 設定正方形位置
	glRotatef(-gAngle*2,0.0f,1.0f,0.0f);					// 旋轉正方形
	glVertexPointer(3, GL_FLOAT, 0, gVerticesSquare);		// 指定頂點陣列
	glTexCoordPointer(2, GL_FLOAT, 0, gTextureSquareCoord);	// 設定紋理座標
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);					// 繪製正方形

	// 關閉頂點陣列
	glDisableClientState(GL_VERTEX_ARRAY);
	// 關閉紋理陣列
	glDisableClientState(GL_TEXTURE_COORD_ARRAY);
	glDisable(GL_TEXTURE_2D);

	// 增加旋轉角度
	gAngle += 2.0f;
}

/************************************************************************/
/*                          JNI程式碼                                     */
/************************************************************************/

extern "C" {
	JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_resize(JNIEnv * env, jobject obj,  jint width, jint height);
	JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_step(JNIEnv * env, jobject obj);
	JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_init(JNIEnv * env, jobject obj);
	JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_setTexture(JNIEnv * env, jclass obj, jintArray tex);
};

JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_resize(JNIEnv * env, jobject obj,  jint width, jint height)
{
	resize(width, height);
}

JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_step(JNIEnv * env, jobject obj)
{
	renderFrame();
}

JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_init(JNIEnv * env, jobject obj)
{
	init();
}

JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_setTexture(JNIEnv * env, jclass obj, jintArray tex)
{
	gTexture = (GLuint *)env->GetIntArrayElements(tex,0);
}