Vfrdtyky

I want to draw a diamond pattern (using 1's) in the zeros matrix 80x80. The first half is going really well but I get nothing but 0s in the second half.

img = np.zeros((80,80))



def draw_pic(image):

    for i in range(len(image)):

        for j in range(len(image[i])):

            print(int(image[i][j]), end = '')

        print()



def gen_diamond(image):

    ret = np.copy(image)

    for i in range(len(image)):

        for j in range(len(image[i])):

            if (i < len(image)/2 and j >= len(image[i])/2 - (i + 1) and j <= len(image[i])/2 + i):

                ret[i][j] = 1

            if (i > len(image)/2 and j >= len(image[i])/2 - (i + 1)and j <= len(image[i])/2 - i):

                ret[i][j] = 1





    return ret



draw_pic(gen_diamond(img))

Your error is in the range checks in the lower half. Let's look at the arithmetic for row 42 ...

        if (i > len(image)/2 and

            j >= len(image[i])/2 - (i + 1) and

            j <= len(image[i])/2 - i):

Substituting the proper values, we have:

        if (42 > 40 and

            j >= 40 - (42 + 1) and

            j <= 40 - 42):

That last condition cannot happen: you need to subtract the row number from the midpoint and take the absolute value. Simpler yet, just set your loop values directly to the ranges you need:

row_mid = len(image) // 2

col_mid = len(image[0]) // 2



for row in range(row_mid):

    for col in range(col_mid-row, col_mid+row):

        print(row, col)

        ret[row, col] = 1



for tmp in range(row_mid):

    row = len(image) - tmp    # Work from the bottom up

    for col in range(col_mid-tmp, col_mid+tmp):

        ret[row, col] = 1 

Output for a 10x10 array:

0000000000

0000110000

0001111000

0011111100

0111111110

0000000000

0111111110

0011111100

0001111000

0000110000

I'll trust you to adjust the boundary conditions. :-)

Here is a solution. It works well on even by even and odd x odd image grids.

img = np.zeros((12,12))





def draw_pic(image):

    for i in range(len(image)):

        for j in range(len(image[i])):

            print(int(image[i][j]), end = '')

        print()



def gen_diamond(image):

    ret = np.copy(image)

    for i in range(len(image)):

        for j in range(len(image[i])):

            if (i < len(image)/2 and j >= len(image[i])/2 - (i + 1) and j <= len(image[i])/2 + i):

                ret[i][j] = 1

            if (i >= len(image)/2 and j >= i-len(image[i])/2 and j <= (3/2*len(image[i])-i)-1):

                ret[i][j] = 1





    return ret



draw_pic(gen_diamond(img))

Output looks like this for 12x12

000001100000

000011110000

000111111000

001111111100

011111111110

111111111111

111111111111

011111111110

001111111100

000111111000

000011110000

000001100000

and this for 11 x 11

00000100000

00001110000

00011111000

00111111100

01111111110

11111111111

01111111110

00111111100

00011111000

00001110000

00000100000