How to Create Awesome Mosaic Picture in Excel with Python

What will we do in this tutorial?

Create a mosaic in Excel using Python.

See the tutorial on YouTube and hear how you can use it as prank!

Step 1: How to create a mosaic from a photo

If you want a deeper description of how to create a mosaic you should read the following tutorial, which shows the code on how to do it.

Step 2: Install the necessary libraries

You need to install OpenCV. If you use PyCharm you can follow this tutorial.

Otherwise you can install the libraries as follows.

pip install opencv-python
pip install numpy
pip install xlsxwriter

Please ask if you have troubles with it.

Step 3: The code used to create the Mosaic in Excel

This will just provide the code for you to enjoy. The process code is used from the tutorial linked above, where it is described.

import cv2
import numpy as np
import xlsxwriter

def create_mosaic_in_excel(photo, box_height, box_width, col_width=2, row_height=15):
    # Get the height and width of the photo
    height, width, _ = photo.shape

    # Create Excel workbook and worksheet
    workbook = xlsxwriter.Workbook('mosaic.xlsx')
    worksheet = workbook.add_worksheet("Urgent")

    # Resize columns and rows
    worksheet.set_column(0, width//box_width - 1, col_width)
    for i in range(height//box_height):
        worksheet.set_row(i, row_height)

    # Create mosaic
    for i in range(0, height, box_height):
        for j in range(0, width, box_width):
            # Create region of interest (ROI)
            roi = photo[i:i + box_height, j:j + box_width]
            # Use numpy to calculate mean in ROI of color channels
            b_mean = np.mean(roi[:, :, 0])
            g_mean = np.mean(roi[:, :, 1])
            r_mean = np.mean(roi[:, :, 2])

            # Convert mean to int
            b_mean_int = b_mean.astype(int).item()
            g_mean_int = g_mean.astype(int).item()
            r_mean_int = r_mean.astype(int).item()

            # Create color code
            color = '#{:02x}{:02x}{:02x}'.format(r_mean_int, g_mean_int, b_mean_int)

            # Add color code to cell
            cell_format = workbook.add_format()
            worksheet.write(i//box_height, j//box_width, "", cell_format)

    # Close and write the Excel sheet

def main():
    photo = cv2.imread("rune.png")

    number_cols = 50
    number_rows = 45

    # Get height and width of photo
    height, width, _ = photo.shape
    box_width = width // number_cols
    box_height = height // number_rows

    # To make sure that it we can slice the photo in box-sizes
    width = (width // box_width) * box_width
    height = (height // box_height) * box_height
    photo = cv2.resize(photo, (width, height))

    # Create the Excel mosaic
    create_mosaic_in_excel(photo.copy(), box_height, box_width, col_width=2, row_height=15)


Step 4: What to modify

The above tutorial assumes a photo of me in rune.png. I used the one taken from this page. You should obviously change it to something else.

You can change how many columns and rows in the Excel sheet the mosaic should be. This is done by changing the values of number_cols and number_rows.

Then you can change the values of col_width=2 and row_height=15.

In the YouTube video I use this free picture from Pexels (download) and modify number_cols = 100 and number_rows = 90, and col_width=1 and row_height=6.


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