《OpenGL ES 2.0 Programming Guide》第9章 “最简单的本地纹理显示”示例代码【C语言版】

#include <stdlib.h>
#include "esUtil.h"
typedef struct
{
    // Handle to a program object
    GLuint programObject;
    // Attribute locations
    GLint  positionLoc;
    GLint  texCoordLoc;
    // Sampler location
    GLint samplerLoc;
    // Texture handle
    GLuint textureId;
} UserData;
///
// Load texture from disk
//
GLuint LoadTexture ( char *fileName )
{
    int width, height;
    char *buffer = esLoadTGA ( fileName, &width, &height );
    GLuint texId;
    if ( buffer == NULL )
    {
        esLogMessage ( "Error loading (%s) image.\n", fileName );
        return 0;
    }
    glGenTextures ( 1, &texId );
    glBindTexture ( GL_TEXTURE_2D, texId );
    glTexImage2D ( GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, buffer );
    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
    free ( buffer );
    return texId;
}
///
// Initialize the shader and program object
//
int Init ( ESContext *esContext )
{
    char *fileName = "D:/Projects/Visual Studio 2012/OpenGL_Demo/opengles-book-samples-master/Windows/Chapter_9/Simple_Texture2D/Fieldstone.tga";
    UserData *userData = esContext->userData;
    GLbyte vShaderStr[] =
        "attribute vec4 a_position;   \n"
        "attribute vec2 a_texCoord;   \n"
        "varying vec2 v_texCoord;     \n"
        "void main()                  \n"
        "{                            \n"
        "   gl_Position = a_position; \n"
        "   v_texCoord = a_texCoord;  \n"
        "}                            \n";
    GLbyte fShaderStr[] =
        "precision mediump float;                            \n"
        "varying vec2 v_texCoord;                            \n"
        "uniform sampler2D s_texture;                        \n"
        "void main()                                         \n"
        "{                                                   \n"
        "  gl_FragColor = texture2D( s_texture, v_texCoord );\n"
        "}                                                   \n";
    // Load the shaders and get a linked program object
    userData->programObject = esLoadProgram ( vShaderStr, fShaderStr );
    // Get the attribute locations
    userData->positionLoc = glGetAttribLocation ( userData->programObject, "a_position" );
    userData->texCoordLoc = glGetAttribLocation ( userData->programObject, "a_texCoord" );
    // Get the sampler location
    userData->samplerLoc = glGetUniformLocation ( userData->programObject, "s_texture" );
    // Load the texture
    //userData->textureId = CreateSimpleTexture2D ();
    userData->textureId = LoadTexture(fileName);
    glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
    return TRUE;
}
///
// Draw a triangle using the shader pair created in Init()
//
void Draw ( ESContext *esContext )
{
    UserData *userData = esContext->userData;
    GLfloat vVertices[] = { -0.5f,  0.5f, 0.0f,  // Position 0
                            0.0f,  0.0f,        // TexCoord 0
                            -0.5f, -0.5f, 0.0f,  // Position 1
                            0.0f,  1.0f,        // TexCoord 1
                            0.5f, -0.5f, 0.0f,  // Position 2
                            1.0f,  1.0f,        // TexCoord 2
                            0.5f,  0.5f, 0.0f,  // Position 3
                            1.0f,  0.0f         // TexCoord 3
                          };
    GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
    // Set the viewport
    glViewport ( 0, 0, esContext->width, esContext->height );
    // Clear the color buffer
    glClear ( GL_COLOR_BUFFER_BIT );
    // Use the program object
    glUseProgram ( userData->programObject );
    // Load the vertex position
    glVertexAttribPointer ( userData->positionLoc, 3, GL_FLOAT,
                            GL_FALSE, 5 * sizeof(GLfloat), vVertices );
    // Load the texture coordinate
    glVertexAttribPointer ( userData->texCoordLoc, 2, GL_FLOAT,
                            GL_FALSE, 5 * sizeof(GLfloat), &vVertices[3] );
    glEnableVertexAttribArray ( userData->positionLoc );
    glEnableVertexAttribArray ( userData->texCoordLoc );
    // Bind the texture
    glActiveTexture ( GL_TEXTURE0 );
    glBindTexture ( GL_TEXTURE_2D, userData->textureId );
    // Set the sampler texture unit to 0
    glUniform1i ( userData->samplerLoc, 0 );
    glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
    eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
}
///
// Cleanup
//
void ShutDown ( ESContext *esContext )
{
    UserData *userData = esContext->userData;
    // Delete texture object
    glDeleteTextures ( 1, &userData->textureId );
    // Delete program object
    glDeleteProgram ( userData->programObject );
}
int main ( int argc, char *argv[] )
{
    ESContext esContext;
    UserData  userData;
    esInitContext ( &esContext );
    esContext.userData = &userData;
    esCreateWindow ( &esContext, "Simple Texture 2D", 512, 512, ES_WINDOW_RGB );
    if ( !Init ( &esContext ) )
        return 0;
    esRegisterDrawFunc ( &esContext, Draw );
    esMainLoop ( &esContext );
    ShutDown ( &esContext );
}