Creating a set of images for image recognition.

iPhone camera gantry to take photos in focus at 3x magnification.

I would like to train an image recognition model with my own images to see how well it works. Here I want to use the obverse of coins to make a model to recognize the portraits of Elizabeth II (younger), Elizabeth II (more mature), George VI and Abraham Lincoln.

Initially I used 5 cent coins but I found they reflected too much light to take a good photograph so I switched to 1 cent coins. I also started with a camera on a Microsoft Surface Pro computer, taking pictures of 9 coins at a time in order to try to be efficient, but I did not get the higher image quality I believe I need.

Microsoft Surface Pro camera taking pictures using a Python program in Google Colab.
Photograph taken using the Surface Pro camera.
Photo taken with iPhone: 3x magnification, square layout, flash on white paper background.

The next step is to remove the background using OpenCV in Python, crop the image to have just the coin. I don’t want to have the image recognition model recognize the portrait because her name is printed on it, so I will crop it again to have only the portrait.

I believe this type of image processing can be applied to historical artifacts photographed using a neutral background. I am concerned the coins are too worn and have too little variation in colour to make a good model but that in itself will be useful to learn if it’s the case.

My thanks to the Saskatoon Coin Club for their excellent page describing the obverse designs of Canadian one cent coins.

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