How to scale an image in Python?

Question

def scaleImage(image):
    """
    A function that takes an image and makes each pixel grayscale:
    the red, blue, green components are the average of the respective
    components in each original pixel.
    """

    pix = image.getPixels()

    # How can I condense the following loop?

    newimage = Image()
    for pixel in pix:
        newpixel = ((int(pixel[0]) + int(pixel[1]) + int(pixel[2]))/3,
                    (int(pixel[0]) + int(pixel[1]) + int(pixel[2]))/3,
                    (int(pixel[0]) + int(pixel[1]) + int(pixel[2]))/3,
                     int(pixel[3]))
        newimage.setPixels(newpixel)

    return newimage

My task is to write a function showScale() that asks the user for an image filename, then displays both that image and its grayscale version in a window.

def showScale():

    filename = raw_input("The name of the image file? ")
    picture = Image.open(filename)
    newpicture = Image.open(scaleImage(picture))
    newpicture.show()

Question1. Should I use cs1graphics module to make it work?

Question2. How should I change my code to answer my task?

Your title is very general. I think you should edit it to be more specific. — senderle
– senderle, Commented Mar 24, 2011 at 0:56
Your grayscaling algorithm is incorrect. It's a weighted average, not a mean. — Ignacio Vazquez-Abrams
– Ignacio Vazquez-Abrams, Commented Mar 24, 2011 at 1:12
@pynator: all the questions from hkus10 seems like homework... — gok
– gok, Commented Mar 24, 2011 at 9:23

Jonathan Root · Accepted Answer · 2013-08-11 16:22:51Z

4

if you are using PIL

greyscaleIm = Image.open(filename).convert("L")

http://effbot.org/imagingbook/introduction.htm

edited Aug 11, 2013 at 16:22

Jonathan Root

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answered Mar 24, 2011 at 0:56

dting

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Comments

gok · Accepted Answer · 2011-03-24 01:09:54Z

-1

although it may be overkill depending on what your ultimate goal is. It is also possible to do it with opencv.

img = cv.LoadImage(image)
gray = cv.cvCreateImage ((img.width, img.height), 8, 1)
cv.cvCvtColor(img, gray, cv.CV_BGR2GRAY)

then show both with

cv.NamedWindow(...
cv.ShowImage(...

answered Mar 24, 2011 at 1:09

gok

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