1.前言

图片如下：纹理坐标为左上角为（0，0），右下角为（1，1）

我们绘制一个正方形,顶点坐标数据如下：

此次代码不包含z轴，默认为0。

要做的事就是把图片贴到正方形的表面，并绘制出正方形。

所以上面的纹理坐标和顶点坐标的顺序要一致。这样绘制的图片才完整。

比如左上角纹理坐标为（0，0）对应顶点坐标为（-0.5 , 0.5）。

因为多加了一组纹理坐标，所以需要修改我们的着色器为：

String vertexShaderCode =
            "attribute vec4 vPosition;\n" +
                    "attribute vec2 vCoordinate;\n" +
                    "uniform mat4 vMatrix;\n" +
                    "\n" +
                    "varying vec2 aCoordinate;\n" +
                    "\n" +
                    "void main(){\n" +
                    "    gl_Position=vMatrix*vPosition;\n" +
                    "    aCoordinate=vCoordinate;\n" +
                    "}";

    String fragmentShaderCode =
            "precision mediump float;\n" +
                    "\n" +
                    "uniform sampler2D vTexture;\n" +
                    "varying vec2 aCoordinate;\n" +
                    "\n" +
                    "void main(){\n" +
                    "    gl_FragColor=texture2D(vTexture,aCoordinate);\n" +
                    "}";

上面着色器中有：

顶点位置句柄：vPosition
矩阵变换句柄：vMatrix
纹理坐标句柄：vCoodinate
纹理图像句柄：vTexture

2.代码：

Activity 和 GLSurfaceView不给出，太简单了。直接看Render

public class MyOtherRender implements GLSurfaceView.Renderer {

    String vertexShaderCode =
            "attribute vec4 vPosition;\n" +
                    "attribute vec2 vCoordinate;\n" +
                    "uniform mat4 vMatrix;\n" +
                    "\n" +
                    "varying vec2 aCoordinate;\n" +
                    "\n" +
                    "void main(){\n" +
                    "    gl_Position=vMatrix*vPosition;\n" +
                    "    aCoordinate=vCoordinate;\n" +
                    "}";

    String fragmentShaderCode =
            "precision mediump float;\n" +
                    "\n" +
                    "uniform sampler2D vTexture;\n" +
                    "varying vec2 aCoordinate;\n" +
                    "\n" +
                    "void main(){\n" +
                    "    gl_FragColor=texture2D(vTexture,aCoordinate);\n" +
                    "}";

    private int mProgram;

    private final float[] sPos={
            -1.0f,1.0f,    //左上角
            -1.0f,-1.0f,   //左下角
            1.0f,1.0f,     //右上角
            1.0f,-1.0f     //右下角
    };
//顶点坐标
    private FloatBuffer bPos;
//纹理坐标
    private FloatBuffer bCoord;
//使用的纹理
    private int textureId;
    //纹理坐标数据
    private final float[] sCoord={
            0.0f,0.0f,
            0.0f,1.0f,
            1.0f,0.0f,
            1.0f,1.0f,
    };

    //所有的句柄
    private int vPositionHandle;
    private int vCoordinateHandle;
    private int vMatrixHandle;
    private int vTextureHandle;

    Context context;
    public MyOtherRender(Context context) {
        this.context = context;
    }

    Bitmap mBitmap = null;
    @Override
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        GLES20.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
        GLES20.glEnable(GLES20.GL_TEXTURE_2D);
        //顶点坐标
        ByteBuffer bb = ByteBuffer.allocateDirect(sPos.length * 4);
        bb.order(ByteOrder.nativeOrder());
        bPos = bb.asFloatBuffer();
        bPos.put(sPos);
        bPos.position(0);
        //纹理坐标
        ByteBuffer cc = ByteBuffer.allocateDirect(sCoord.length * 4);
        cc.order(ByteOrder.nativeOrder());
        bCoord = cc.asFloatBuffer();
        bCoord.put(sCoord);
        bCoord.position(0);

        mBitmap = BitmapFactory.decodeResource(context.getResources() , R.drawable.bj);

        int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER,
                vertexShaderCode);
        int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER,
                fragmentShaderCode);
        mProgram = GLES20.glCreateProgram();
        GLES20.glAttachShader(mProgram, vertexShader);
        GLES20.glAttachShader(mProgram, fragmentShader);
        GLES20.glLinkProgram(mProgram);

    }

    private final float[] mMVPMatrix = new float[16];
    private final float[] mProjectMatrix = new float[16];
    private final float[] mViewMatrix = new float[16];
    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        GLES20.glViewport(0, 0, width, height);
        float ratio = (float) width / height;
        Matrix.frustumM(mProjectMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
        //设置相机位置
        Matrix.setLookAtM(mViewMatrix, 0, 0, 0, 7.0f, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
        //计算变换矩阵
        Matrix.multiplyMM(mMVPMatrix, 0, mProjectMatrix, 0, mViewMatrix, 0);
    }


    @Override
    public void onDrawFrame(GL10 gl) {
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
        GLES20.glUseProgram(mProgram);

        //获取所有句柄
        vPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
        vCoordinateHandle = GLES20.glGetAttribLocation(mProgram, "vCoordinate");
        vTextureHandle = GLES20.glGetUniformLocation(mProgram, "vTexture");
        vMatrixHandle = GLES20.glGetUniformLocation(mProgram, "vMatrix");

        GLES20.glUniformMatrix4fv(vMatrixHandle, 1, false, mMVPMatrix, 0);
        GLES20.glEnableVertexAttribArray(vPositionHandle);
        GLES20.glEnableVertexAttribArray(vCoordinateHandle);
        GLES20.glUniform1i(vTextureHandle, 0);
        textureId = createTexture();

        //传入顶点坐标 没有给z轴设置坐标
        GLES20.glVertexAttribPointer(vPositionHandle, 2, GLES20.GL_FLOAT, false, 0, bPos);
        //传入纹理坐标
        GLES20.glVertexAttribPointer(vCoordinateHandle, 2, GLES20.GL_FLOAT, false, 0, bCoord);
        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
    }

    private int createTexture(){
        int[] texture=new int[1];
        if(mBitmap!=null&&!mBitmap.isRecycled()){
            //生成纹理
            GLES20.glGenTextures(1,texture,0);
            //生成纹理
            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D,texture[0]);
            //设置缩小过滤为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
            GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER,GLES20.GL_NEAREST);
            //设置放大过滤为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.glTexParameterf(GLES20.GL_TEXTURE_2D,GLES20.GL_TEXTURE_MAG_FILTER,GLES20.GL_LINEAR);
            //设置环绕方向S，截取纹理坐标到[1/2n,1-1/2n]。将导致永远不会与border融合
            GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S,GLES20.GL_CLAMP_TO_EDGE);
            //设置环绕方向T，截取纹理坐标到[1/2n,1-1/2n]。将导致永远不会与border融合
            GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T,GLES20.GL_CLAMP_TO_EDGE);
            //根据以上指定的参数，生成一个2D纹理
            GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, mBitmap, 0);
            return texture[0];
        }
        return 0;
    }

    //编译着色器
    public static int loadShader(int type, String shaderCode){
        int shader = GLES20.glCreateShader(type);
        GLES20.glShaderSource(shader, shaderCode);
        GLES20.glCompileShader(shader);
        return shader;
    }

}

纹理贴图运行效果如上，但是有个问题就是，运行一段时间之后，程序会自动退出。求解？

有时候为了使我们的图片不变形，我们需要修改投影矩阵，所以，部分代码改为：

 @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        GLES20.glViewport(0, 0, width, height);
        int w = mBitmap.getWidth();
        int h = mBitmap.getHeight();
        float sWH = w / (float) h;
        float sWidthHeight = width / (float) height;
        if (width > height) {
            if (sWH > sWidthHeight) {
                Matrix.orthoM(mProjectMatrix, 0, -sWidthHeight * sWH, sWidthHeight * sWH, -1, 1, 3, 7);
            } else {
                Matrix.orthoM(mProjectMatrix, 0, -sWidthHeight / sWH, sWidthHeight / sWH, -1, 1, 3, 7);
            }
        } else {
            if (sWH > sWidthHeight) {
                Matrix.orthoM(mProjectMatrix, 0, -1, 1, -1 / sWidthHeight * sWH, 1 / sWidthHeight * sWH, 3, 7);
            } else {
                Matrix.orthoM(mProjectMatrix, 0, -1, 1, -sWH / sWidthHeight, sWH / sWidthHeight, 3, 7);
            }
        }
//        float ratio = (float) width / height;
//        Matrix.frustumM(mProjectMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
        //设置相机位置
        Matrix.setLookAtM(mViewMatrix, 0, 0, 0, 7.0f, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
        //计算变换矩阵
        Matrix.multiplyMM(mMVPMatrix, 0, mProjectMatrix, 0, mViewMatrix, 0);

OpenGL ES (16): 纹理贴图

1.前言

2.代码：

猜你喜欢