How to get coordinate of only one item in numpy array

Question

So this is my code. I don't want to get all the coordinates of pixel values below 210 because I want to perform some operation on them and possibly adjust the condition depending on outcome of that operation.

filename = "/home/User/PycharmProjects/Test/files/1366-000082.png"

image = Image.open(filename)

image_data = np.asarray(image, dtype='int64')

def get_image_data():
     for row in image_data:
         for cell in row:
             if condition:
                 # I need only coordinate of cell here

So again I am aware of the argwhere function. But that only gets me all the coordinates. But I might want to change that condition somewhere in the loop.

Is this even possible?

Otherwise I have to use Pillow, but then the loop will be 10x slower.

What imports are you using? You reference Image.open which looks like it's from PIllow, but then you make it sound like you don't want to use Pillow? How are you trying to call 'get_image_data()'? — Tom Johnson
– Tom Johnson, Commented Dec 15, 2018 at 18:55
I use Pillow, I suppose I was too lazy to change it to cv2 as I started out with Pillow. And it is pretty fast. — TheProgramMAN123
– TheProgramMAN123, Commented Dec 15, 2018 at 19:36

nick nick · Accepted Answer · 2018-12-15 19:43:14Z

1

You can use enumerate() to get value indexes:

def get_image_data():
    for row_number, row in enumerate(image_data):
        for column_number, cell in enumerate(row):
            if condition:
                # I need only coordinate of cell here
                print(row_number, column_number)

and, maybe you should pass image_data to get_image_data method

answered Dec 15, 2018 at 19:43

nick nick

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Nicholas Smith · Accepted Answer · 2018-12-15 19:00:11Z

0

Have you looked at using a mask? It should make your life much simpler and faster as with the built in functions of a numpy array you wouldn't have to loop through the entire thing.

As an example for you:

A = np.random.randint(1, 500, (100,100)) Mask = A < 210

This would then give you a matrix of True/False values that you could essentially query and adjust the entries as you want. I know you don't want to deal with all of the coordinates, but this would be much faster than looping through your pixel values.

Hopefully that helps you

answered Dec 15, 2018 at 19:00

Nicholas Smith

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