How to Hide Two Images in Three Slides

In this little project, we will print three slides containing two hidden images.

The two images are revealed when the slides are stacked in the correct orientation.

Applause from the amazed audience is guaranteed!👏

This project was inspired by the brilliant artwork of Petros Vrellis.

1. Essential Parts:

1x Transparency films for inkjet printers

Total cost of essential parts will be approx. 15,- €/$ as of October 2024

2. Optional parts:

1x Punch pliers for punching 3.2 mm (1/8") holes in the slides

1x Light table with battery for slide presentation

Total cost of optional parts will be approx. 46,- €/$ as of October 2024

You will also need a 3D printer to print the slide holder described in the next chapter.

If you want to edit the source code of the program that generates the slides, you will need a MS Windows PC with Visual Studio installed.

Download the Image Merger Holder.stl 3D printing file at the end of this chapter.

Parts are printed on a 3D FFF printer that should have a build area of at least 200x200mm. (7.9x7.9").

Standard PLA is sufficient for printing material. Infill = 30%, print accuracy = 0.2 mm.

The dimensions of the slide holder are suitable for slides that are printed in the A4 page format. Rescale the slide holder for other formats.

Insert two M3 screws through the holes in the slides holder.

Simply download the PDF file at the end of this chapter, and print it out on transparencies.

In the Print menu, select the option to fit the pages to the print area.

Use the Punch Pliers to punch two 3.2 mm (1/8") holes at the marked positions on each slide.

If you want to try your own images, you will need to install the Image Merger program on your Windows computer.

1. Download the Image.Merger.Setup ZIP file to your Windows PC.
2. Unzip and run the setup.exe program, then follow the instructions. You may be prompted to install .NET Desktop Runtime 8.0.8 (x64) as a prerequisite.

1. In the program, click on one of the five images and select an alternative image of your choice.
2. Click the Merge Images button to merge the three source images and two merge images.
3. Click the Show Merged Images button to see what the images will look like when they are placed on top of each other.
4. When you are satisfied with the result, click the Save Merged Images button to save the resulting images as a PDF file. Print the contents of the PDF file on three transparencies as described in Step 2.
5. Clicking the Reset Images button restores the original images.

Please keep these points in mind when experimenting with your own images:

1. Avoid high contrast such as dark hair, white beards, etc.
2. The background colors of the merged images should be the same.
3. Image resolution should be 1200x1200 pixels or less.

You can download the source code from Github.

This program was written using the free-of-charge MS Visual Studio Community Edition 2022.