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+--- Thread: How it is possible that Gimp while exporting histogram counts more pixels than there (/Thread-How-it-is-possible-that-Gimp-while-exporting-histogram-counts-more-pixels-than-there)
How it is possible that Gimp while exporting histogram counts more pixels than there - niitard - 06-12-2020
Hello,
I'm currently learning programming in python, one of subject that i'm trying to cover now is working with image. So i wanted to created o program that's counting how many pixel of each colour is in my image (which is 10x10 pixel gray scale). So i created the image all black with 24 white pixel and my program, all works well. It counts 24 pixel of "255" and 76 of "0.
But here comes the problem:
when i have used the Gimp [color] -> [information] -> [export histogram] to file i got the results like this
Range start,Value
0 , 76.0
1 , 0.0
2 , 0.0
[...]
253 , 0.0
254 , 24.0
255 , 24.0
it looks like, the Gimp software counted white pixel two times, so when they are summed up that makes 24 + 24 + 76 = 124 , and yet the picture size is still 10x10 = 100
i've searched the internet but cant find the clue:
How it is possible that Gimp while exporting histogram counts more pixels than there are really in the picture?
Thank you for help
RE: How it is possible that Gimp while exporting histogram counts more pixels than there - Ofnuts - 06-12-2020
Yes, likely a bug, nice finding.
Didn't see you code, but if you access each pixel in turn using get_pixel(), you code will not scale to real-life images. In Python your can use "pixel regions", which is a nbig array-like structure that you can access in Python (it even supports slices).
RE: How it is possible that Gimp while exporting histogram counts more pixels than there - niitard - 06-12-2020
(06-12-2020, 03:40 PM)Ofnuts Wrote: Yes, likely a bug, nice finding.
Didn't see you code, but if you access each pixel in turn using get_pixel(), you code will not scale to real-life images. In Python your can use "pixel regions", which is a nbig array-like structure that you can access in Python (it even supports slices).
from PIL import Image
import numpy as np
img = Image.open('start.bmp')
arr=np.array(img)
print (arr)
#im still learning arrays so i changed it to list that im more familiar with
b=arr.tolist()
print ()
flat_list=[]
for sublist in b:
for item in sublist:
flat_list.append(item)
white_dots=0
black_dots=0
for i in flat_list:
if i == 255:
white_dots+=1
if i == 0:
black_dots+=1
print ('number 255: ', white_dots)
print ('number 0: ', black_dots)
thats my code
thank you very much
RE: How it is possible that Gimp while exporting histogram counts more pixels than there - Ofnuts - 06-12-2020
Oh, I thought you where doing a Python Gimp script...
You may be more familiar with lists, but the numpy array is much faster. Not as bad as a Gimp get_pixel() but for real-size images numpy will make a very significant difference.
RE: How it is possible that Gimp while exporting histogram counts more pixels than there - niitard - 06-12-2020
(06-12-2020, 04:16 PM)Ofnuts Wrote: Oh, I thought you where doing a Python Gimp script...
You may be more familiar with lists, but the numpy array is much faster. Not as bad as a Gimp get_pixel() but for real-size images numpy will make a very significant difference.
Thank you