Gimp python-fu how do I select a polygon?

Question

Problem

I have the need to make a polygonal selection on an image hundreds of times. To help, I have been trying to use the python console to create a script that will do this in a calculated fashion (same size area, hundreds of different start points). I am using GIMP 2.8.18 on a Windows 10 machine.

The problem is that the function pdb.gimp_image_select_polygon does not seem to function.

Code

Here is the bare bones of what I am trying to do in the python console:

    theImage = gimp.image_list()[0]
    OP_ADD = 0
    POINT_COUNT = 5
    x = 0
    y = 0
    points = [0.0 for i in range(0,10)]
    points[0] = 64.0 + (128.0 * x)
    points[1] = 64.0 * y
    points[2] = 128.0 * x
    points[3] = 32.0 + (64.0 * y)
    points[4] = 64.0 + (128.0 * x)
    points[5] = 64.0 + (64.0 * y)
    points[6] = 128.0 + (128.0 * x)
    points[7] = 32.0 + (64.0 * y)
    points[8] = 64.0 + (128.0 * x)
    points[9] = 64.0 * y
    pdb.gimp_image_select_polygon(theImage, OP_ADD, POINT_COUNT, points)

When this runs, nothing happens. OTOH, if I use another selection function, I get a selection:

    pdb.gimp_image_select_rectangle(theImage, 0, 64 ,0 ,128 ,32)

I get no traceback errors using gimp_image_select_polygon, so I know I have the correct number of parameters and the correct types of parameters. I've tried various things and am unable to find much help online.

Does anyone see a problem with my code, or is the python engine in GIMP totally fubar?

Answer 1

The length argument is the number of coordinates, not the number of points (so, typically, the double)

OP_REPLACE isn't defined in my version.

For a 100x100 square at (100,100):

p=[100,100,100,200,200,200,200,100]
pdb.gimp_image_select_polygon(image, CHANNEL_OP_REPLACE,len(p),p)