Texture in QGLWidget

[showhand]

Hi, all

In the scene, I make an image by using large size of data. And I need to do some other operations on the drawed image. Take drawing lines by move mouse for example. As anybody know, the image will be repainted when the mouse moving and this make the speed very slow!! I want to use texture to solve the proble. But the texture size is limited as 64,128 or 256. My image size can't be limited.

1. How can I use texture but not limit?
2. Or is there any other way to speed up?
3. I use gluBuild2DMipmaps(), but the color of my drawed lines won't be correctly display. And why?

Does anybody can help me, thanks in advance!!