LTexture.h

bool loadPixelsFromFile( std::string path );
bool loadTextureFromFileWithColorKey( std::string path, GLubyte r, GLubyte g, GLubyte b, GLubyte a = 000 );
bool loadTextureFromPixels32();

LTexture.cpp

bool LTexture::loadPixelsFromFile( std::string path )
{
    freeTexture();
    bool pixelsLoaded = false;
    ILuint imgID = 0;
    ilGenImages( 1, &imgID );//生成ID
    ilBindImage( imgID );//绑定
    ILboolean success = ilLoadImage( path.c_str() );//加载图片
    if( success == IL_TRUE )
    {
        success = ilConvertImage( IL_RGBA, IL_UNSIGNED_BYTE );//转为rgba
        if( success == IL_TRUE )
        {
            GLuint imgWidth = (GLuint)ilGetInteger( IL_IMAGE_WIDTH );//获取图片宽高
            GLuint imgHeight = (GLuint)ilGetInteger( IL_IMAGE_HEIGHT );
            GLuint texWidth = powerOfTwo( imgWidth );//计算对应的二次幂
            GLuint texHeight = powerOfTwo( imgHeight );
            if( imgWidth != texWidth || imgHeight != texHeight )
            {
                iluImageParameter( ILU_PLACEMENT, ILU_UPPER_LEFT );//将图片放在左上角
                iluEnlargeCanvas( (int)texWidth, (int)texHeight, 1 );//调整图像大小
            }
            GLuint size = texWidth * texHeight;
            mPixels = new GLuint[ size ];
            mImageWidth = imgWidth;
            mImageHeight = imgHeight;
            mTextureWidth = texWidth;
            mTextureHeight = texHeight;
            memcpy( mPixels, ilGetData(), size * 4 );//把像素copy到mPixels
            pixelsLoaded = true;
        }
        ilDeleteImages( 1, &imgID );
    }
    if( !pixelsLoaded )
    {
        printf( "Unable to load %s\n", path.c_str() );
    }
    return pixelsLoaded;
}

bool LTexture::loadTextureFromFileWithColorKey( std::string path, GLubyte r, GLubyte g, GLubyte b, GLubyte a )
{
    if( !loadPixelsFromFile( path ) )
    {
        return false;
    }
    GLuint size = mTextureWidth * mTextureHeight;
    for( int i = 0; i < size; ++i )//遍历每一个像素
    {
        //Get pixel colors
        GLubyte* colors = (GLubyte*)&mPixels[ i ];//mPixels[ i ]是32位，rgba各占8位，GLubyte是8位，强转为8位指针指向即可分别对rgba分量操作
        if( colors[ 0 ] == r && colors[ 1 ] == g && colors[ 2 ] == b && ( 0 == a || colors[ 3 ] == a ) )
        {//下面四句设置为透明
            colors[ 0 ] = 255;
            colors[ 1 ] = 255;
            colors[ 2 ] = 255;
            colors[ 3 ] = 000;
        }
    }
    return loadTextureFromPixels32();
}
bool LTexture::loadTextureFromPixels32()
{
    bool success = true;
    if( mTextureID == 0 && mPixels != NULL )
    {
        glGenTextures( 1, &mTextureID );
        glBindTexture( GL_TEXTURE_2D, mTextureID );
        glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, mTextureWidth, mTextureHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, mPixels );//创建纹理
        glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
        glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
        glBindTexture( GL_TEXTURE_2D, NULL );
        GLenum error = glGetError();
        if( error != GL_NO_ERROR )
        {
            printf( "Error loading texture from %p pixels! %s\n", mPixels, gluErrorString( error ) );
            success = false;
        }
        else
        {
            delete[] mPixels;
            mPixels = NULL;
        }
    }
    else
    {
        printf( "Cannot load texture from current pixels! " );
        if( mTextureID != 0 )
        {
            printf( "A texture is already loaded!\n" );
        }
        else if( mPixels == NULL )
        {
            printf( "No pixels to create texture from!\n" );
        }
        success = false;
    }
    return success;
}

LUtil.cpp

bool initGL(){
　　...
　　glEnable( GL_BLEND );//启用混合
　　glDisable( GL_DEPTH_TEST );
　　glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
　　...
}
bool loadMedia()
{
    if( !gCircleTexture.loadTextureFromFileWithColorKey( "circle.png", 000, 255, 255 ) )
    {
        printf( "Unable to load circle texture!\n" );
        return false;
    }
    return true;
}
void render()
{
    glClear( GL_COLOR_BUFFER_BIT );
    glColor4f( 1.f, 1.f, 1.f, 0.5f );
    gCircleTexture.render( ( SCREEN_WIDTH - gCircleTexture.imageWidth() ) / 2.f, ( SCREEN_HEIGHT - gCircleTexture.imageHeight() ) / 2.f );
    glutSwapBuffers();
}