image quality is bad when zoom factors >= 1.0 ?!


In my application i use the OGL function “glDrawPixels” to draw images into screen; when the zoom factor(modified by glPixelZoom) is >= 1.0, the image quality becomes bad(a small rectangles appear on the screen replacing each pixel). i am searching a way to avoid this image quality (pixelization). I know that we can do it if we use texture mapping whit parameter “GL_LINEAR” in the OGL function “glTexParameteri”, but i draw with “glDrawPixels”.
can anyone help!
(sorry for bad english)