On 2006-08-09, Dean Card <[EMAIL PROTECTED]> wrote:
> Okay, so here is the situation. I have need to do some on-the-fly image
> creation. I have everything working great except for the last part of it,
> applying a perspective type transform to the image. The transform will take
> a rectangular 2D image and transform it to a 3D representation in 2D.
>
> Please see the link to see what I am trying to do:
> http://seanberry.com/transform.png
>
> I have PIL v1.15 installed which has a PERSPECTIVE transform, but it does
> not appear to do what I want - or I can't figure out how to use it correctly
> because it is using a transform matrix's coefficients.
>
> Here is the only info I could find on the usage:
> http://mail.python.org/pipermail/image-sig/2005-February/003198.html
This looks like a correct description of the sources:
In Image.py:
elif method == PERSPECTIVE:
# change argument order to match implementation
data = (data[2], data[0], data[1],
data[5], data[3],
data[4],
data[6],
data[7])
and then in Geometry.c:
static int
perspective_transform(double* xin, double* yin, int x, int y, void*
data)
{
double* a = (double*) data;
double a0 = a[0]; double a1 = a[1]; double a2 = a[2];
double a3 = a[3]; double a4 = a[4]; double a5 = a[5];
double a6 = a[6]; double a7 = a[7];
xin[0] = (a0 + a1*x + a2*y) / (a6*x + a7*y + 1);
yin[0] = (a3 + a4*x + a5*y) / (a6*x + a7*y + 1);
return 1;
}
> This is for the creation of images to be used in Flash. Originally I was
> doing the image processing in Flash because Flash 8 has a BitmapData class
> which does the basics of images, copy, transform, etc. To accomplish the
> transform I was using an algorithm that approximated triangles to fill and
> worked really well, but I need the image processing to be server side, not
> client.
>
> So, here I am. Anyone have any idea how to accomplish my goal here? Is
> there a way to fill a triangle with a bitmap using PIL? What about better
> docs on the PERSPECTIVE transform?
>
> Thanks for any and all help on this.
Something like this is almost what you what:
im = im.transform(im.size, Image.PERSPECTIVE, (1, 0, 0, 0, 1, 0, -0.004, 0))
But the problem really is that the top row of the image is at at y of
0-- I think you want the origin of the image to be in the centre for
this to work properly.
Is there a way to do that in PIL?
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