triangulated delauny vertex colours from image

ProtFx.py

# Dealga McArdle 2015 April 22.

import bpy
import mathutils
from mathutils import Vector, Matrix

D = bpy.data  

# access image, get pixels
img_name = 'Buzz_Aldrin_on_moon-thumb-590x499-82071.jpg'
img = D.images[img_name]

# flat r,g,b,a,r,g,b,a...
pxs = list(img.pixels)   

# nested [[r,g,b,a],[r,g,b,a],...]
num_values = len(pxs)  
nested_rgba_list = [pxs[i:i+4] for i in range(num_values)[::4]] 
  
# px dims
px_wide = img.size[0]  # 590
px_high = img.size[1]  # 499

# mesh dimensions, match these with your target mesh.
# protip: use import image as planes addon
# match the size of your triangulated mesh to the rect
# generated by image as plane
x_wide = 1.18236  
y_high = 1.0

# first how wide/tall is a pixel in this scene?
real_x = x_wide / px_wide
real_y = y_high / px_high
offs_x = real_x / 2
offs_y = real_y / 2

def idx_to_co(idx, width):
    # the image starts bottom left
    r = int(idx / width)  
    c = idx % width  
    return r, c 

def generate_tree(vt):
    size = len(vt)
    kd = mathutils.kdtree.KDTree(size)

    for i, vtx in enumerate(vt):
        kd.insert(Vector(vtx), i)
    kd.balance()
    return kd

def get_pretend_pixels(indexed_pixels):
    # let's pretend we get colour from the middle of the pixel
    # this means offsetting the coordinates by half the real pixel sizes
    pretend_pixels = []
    add_pretend_px = pretend_pixels.append

    for i, px in enumerate(indexed_pixels):
        r, c = idx_to_co(i, px_wide)
        x = offs_x + (c * real_x)
        y = offs_y + (r * real_y)
        add_pretend_px([x, y, 0])
        
    return pretend_pixels

pretend_pixels = get_pretend_pixels(nested_rgba_list)
kdtree = generate_tree(pretend_pixels)

obj = bpy.data.objects['Sv_0.001']
mesh = obj.data

# for every vertex in delauny mesh, 
#    find its closest ordered px idx, (this gives us idx->color)
nearest_fake_vertex = []
add_fake = nearest_fake_vertex.append
for i, vtx in enumerate(mesh.vertices):
    co, index, dist = kdtree.find(vtx.co)
    add_fake(index)

color_layer = mesh.vertex_colors['Col']

# for every face in data.polygons
#    for every indexed vertex of the face
#        assign associated colour to colourmap index.
i = 0
for poly in mesh.polygons:
    print(poly.loop_indices)
    for idx in poly.loop_indices:
        loop = mesh.loops[idx]
        v = loop.vertex_index
        
        f = nearest_fake_vertex[v]
        color = nested_rgba_list[f]
        color_layer.data[i].color = color[:3]
        i +=1

note, this doesn't create the Vertex plane / Triangulation for you, that's a separate step you do before all this.