Re: [PyOpenGL-Users] Upcoming fix may cause minor incompatibility...

[Mike C. F. <mcf...@ro...>]

Just to expand a little on this:

    glDrawPixelsXX previously was working on the assumption that the
    graphics passed to it were stored such that array[0] was the first
    row.  This meant that if you did array.tostring() and passed the
    array dimensions in to glDrawPixels you would wind up with a trashed
    image (since Numpy packs arrays to strings from the lowest dimension
    up).  By switching to assuming that array[0] gives the first column
    of the image (that is, that the first dimension represents the index
    *into* the first row), we are basically using the natural order of
    the array and also making the two types of glDrawPixels calls match
    up as expected; so that array[20,30] is the pixel twenty from the
    right and 30 from the bottom, and dumping to a string and passing
    array dimensions works the same as passing in the array.

I've so far come across 1 instance of an incompatibility in 
OpenGLContext.  It actually turned out to be quite nasty (the 
work-around works fine, but figuring out how to eliminate the huge 
series of convolutions through which the code goes at the moment has 
been a bit of a pain...).

Have fun all,
Mike

Mike C. Fletcher wrote:

> I've just checked in changes on the 2.0.1 maintenance branch that fix 
> a bug in how glDrawPixelsXX (that is, all glDrawPixels calls which 
> take an array argument, rather than a string) operates.  The code was 
> previously (unintentionally) reversing the first and second arguments, 
> so that it would take (height,width) rather than (width,height) from 
> the array to decide how to render it.
>
> If you have any code that uses glDrawPixelsXX you will find that this 
> fix causes your code to stop working.  Solution is simply to use 
> properly-sized arrays (i.e. if you want an image 300x100 pixels wide 
> it's shape should be (300,100,depth), rather than (100,300,depth)).  
> If you can't make that change, then simply assigning array.shape = 
> (array.shape[1],array.shape[0]) + array.shape(2:])  will allow you to 
> continue operating as before.
>
> This bug does not affect string-based glDrawPixels calls.
>
> Enjoy yourselves,
> Mike

________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com