罗大柚OpenGL ES教程系列_LessonY_使用2D纹理渲染文字

在创建OpenGL场景时，我们常常需要在场景中渲染一些文字，如在游戏结束时，你需要显示一个“Game Over” 字样。 下面我在GLKit框架下写了一个方法，代码详细描述如下：

//用文字作为image
-(UIImage *) imageWithText:(NSString *)text
                  fontName:(NSString *)fontName
                     color:(UIColor *)color
                     width:(float)width
                    height:(float)height
                rightAlign:(BOOL) rightAlign
{
    
	CGRect textRect = [text boundingRectWithSize:CGSizeMake(width, height)
                                         options:NSStringDrawingUsesLineFragmentOrigin
                                      attributes:@{NSFontAttributeName:[UIFont fontWithName:fontName size:60.0]}
                                         context:nil];
    
    CGSize expectedLabelSize = textRect.size;
    
    float offsetX = rightAlign ? (width - expectedLabelSize.width) : 0.0f;
    UIImage *image2 = [[UIImage alloc] init];
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(width, height), YES, 1);
    [image2 drawInRect:CGRectMake(offsetX,
                                  expectedLabelSize.height / 2.0,
                                  expectedLabelSize.width,
                                  expectedLabelSize.height)
             blendMode:kCGBlendModeNormal
                 alpha:1.0f];
    [image2 drawAtPoint:CGPointMake(offsetX, 0.0f)];
    [text drawAtPoint:CGPointMake(offsetX,0.0f)
       withAttributes:@{NSFontAttributeName:[UIFont fontWithName:fontName size:36.0],
                        NSForegroundColorAttributeName: color}];
    
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return result;
}

然后，按照下面的方式调用上述方法：

UIImage *image = [self imageWithText:@"齐天大圣到此一游" fontName:@"Helvetica" color:[UIColor   greenColor] width:300.0 height:100.0 rightAlign:YES];
    
    //设置纹理
    CGImageRef imageRef = [image CGImage];
    
    //接受一个CGImgaeRef并创建一个新的包含CGImageRef的像素数据的OpenGL ES 纹理缓存
    GLKTextureInfo *textureInfo = [GLKTextureLoader textureWithCGImage:imageRef options:nil error:NULL];
    self.effect.texture2d1.name = textureInfo.name;
    self.effect.texture2d1.target = textureInfo.target;

由于用2D纹理绘制文字的原理比较简单，只需要看懂

-(UIImage *) imageWithText:(NSString *)text
                  fontName:(NSString *)fontName
                     color:(UIColor *)color
                     width:(float)width
                    height:(float)height
                rightAlign:(BOOL) rightAlign  

方法就OK，整个十分方便。

最后是源码下载地址： http://download.csdn.net/detail/luozhonglan/7187875