When I convert depth map to 3D point cloud, I found there is a term called scaling factor. Can anyone give me some idea what scaling factor actually is. Is there any relationship between scaling factor and focal length. The code is as follows:
import argparse
import sys
import os
from PIL import Image
focalLength = 938.0
centerX = 319.5
centerY = 239.5
scalingFactor = 5000
def generate_pointcloud(rgb_file,depth_file,ply_file):
rgb = Image.open(rgb_file)
depth = Image.open(depth_file).convert('I')
if rgb.size != depth.size:
raise Exception("Color and depth image do not have the same
resolution.")
if rgb.mode != "RGB":
raise Exception("Color image is not in RGB format")
if depth.mode != "I":
raise Exception("Depth image is not in intensity format")
points = []
for v in range(rgb.size[1]):
for u in range(rgb.size[0]):
color = rgb.getpixel((u,v))
Z = depth.getpixel((u,v)) / scalingFactor
print(Z)
if Z==0: continue
X = (u - centerX) * Z / focalLength
Y = (v - centerY) * Z / focalLength
points.append("%f %f %f %d %d %d 0\n"%
In this context "scaling factor" refers to the relation between depth map units and meters; it has nothing to do with the focal length of the camera.
Depth maps are typically stored in 16-bit unsigned integers at millimeter scale, thus to obtain Z value in meters, the depth map pixels need to be divided by 1000. You have a somewhat unconventional scaling factor of 5000, meaning that the unit of your depth maps is 200 micrometers.