OpenGL ES纹理尺寸限制的处理方法

快来打我* 2022-09-28 13:14 287阅读 0赞

大家都知道，OpenGL ES对纹理的尺寸有限制，就是长和宽都必须是2的整数次幂。（实际上OpenGL都有此限制，但有一些扩展可以解决此问题）。因此处理方案有两种：

1.  将纹理尺寸限制为2的整数次幂。比如，我有一个480×320的背景图案，我可以用Photoshop将画布设置为512×512，在纹理映射时只使用480×320部分。当然我也可以将多个图案合成在一个纹理中，在纹理映射时根据图案的位置进行映射。
2.  仍然使用正常的图像尺寸，但在使用时进行转换。下面是源代码：

<table> 
 <tbody> 
 <tr> 
 <td> 
 <div>
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 </div> </td> 
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 &nbsp; &nbsp; &nbsp; &nbsp; 
 // 首先调整纹理的长和宽为2的整数次幂 &nbsp; &nbsp; &nbsp; &nbsp; 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 if 
 ( 
 ( _width 
 ! 
 = 1 
 ) 
 &amp;&amp; 
 ( _width 
 &amp; 
 ( _width 
 - 1 
 ) 
 ) 
 ) 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 { 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; i 
 = 
 1 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 
 while 
 ( 
 ( sizeToFit 
 ? 2 
 * i 
 : i 
 ) 
 &lt; _width 
 ) 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; i 
 * 
 = 
 2 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; _width 
 = i 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 } 
 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 if 
 ( 
 ( _height 
 ! 
 = 1 
 ) 
 &amp;&amp; 
 ( _height 
 &amp; 
 ( _height 
 - 1 
 ) 
 ) 
 ) 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 { 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; i 
 = 
 1 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 
 while 
 ( 
 ( sizeToFit 
 ? 2 
 * i 
 : i 
 ) 
 &lt; _height 
 ) 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; i 
 * 
 = 
 2 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; _height 
 = i 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 } 
 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 // 如果调整后的图像尺寸大于最大纹理尺寸（1024），那么需要缩小 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 while 
 ( 
 ( _width 
 &amp; gt 
 ; kMaxTextureSize 
 ) 
 || 
 ( _height 
 &amp; gt 
 ; kMaxTextureSize 
 ) 
 ) 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 { 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; _width 
 / 
 = 
 2 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; _height 
 / 
 = 
 2 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; transform 
 = CGAffineTransformScale 
 ( transform, 0.5, 0.5 
 ) 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; imageSize. 
 x 
 * 
 = 
 0.5 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; imageSize. 
 y 
 * 
 = 
 0.5 
 ; 
 &nbsp; &nbsp; &nbsp; &nbsp; 
 } 
 </div> </td> 
 </tr> 
 </tbody> 
</table>