Quad Perspective Transformation

[Kamilche]

I have a need to tile a bitmap across an arbitrary quadrilateral, and
apply perspective to it.
The Python Imaging Library (PIL) has an undocumented function that
might work, but I can't figure out how to make it work. You're
supposed to pass it 8 parameters, a b c d e f g h .

What I want is to take a rectangular texture map and 'flop it down on
the floor' - pinch in the left and right with perspective, and squash
down the top with perspective. I've modified those 8 parameters and
examined the results, but that hasn't brought me any closer to my
goal.

The PIL function is this:

im2 = im.transform(im.size, Image.PERSPECTIVE, (1, 0, 0, 0, 1, -100,
0, .001), Image.BILINEAR)

Here's hoping someone can shed some light on this function!

[Gabriel Genellina]

En Thu, 01 Feb 2007 13:46:37 -0300, Kamilche <kl*******@comcast.net>
escribió:

I have a need to tile a bitmap across an arbitrary quadrilateral, and
apply perspective to it.
The Python Imaging Library (PIL) has an undocumented function that
might work, but I can't figure out how to make it work. You're
supposed to pass it 8 parameters, a b c d e f g h .

I don't know exactly how it's implemented, but the usual perspective
transformation matrix has exactly 8 non zero parameters. Any text on
computer graphics should cover it. My first hit on Google:
http://bishopw.loni.ucla.edu/AIR5/2Dperspective.html

--
Gabriel Genellina