Choose a clear photo with strong outlines and simple details
Open the image in an editing app or online converter
Convert the image to grayscale
Increase contrast to make edges more visible
Apply a sketch, edge-detection, or outline filter
Remove or lighten the background if needed
Clean up stray marks and unwanted details
Thicken important lines for easier coloring
Simplify overly complex areas
Invert the image if the tool requires it
Adjust brightness and contrast until the lines look clean
Save the result as a high-resolution image or PDF
Print the image on white paper
Test the page by checking that the lines are clear and bold